IBM Switch 12122EA6 User Manual
Cisco Systems Intelligent Gigabit Ethernet  
Switch Modules for the IBM BladeCenter  
Software Configuration Guide  
Cisco IOS Release 12.1(22)EA6  
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C O N T E N T S  
Preface xxiii  
Audience xxiii  
Purpose xxiii  
Conventions xxiv  
Related Publications xxv  
CHAPTER  
1
Overview 1-1  
Features 1-1  
Ease of Use and Ease of Deployment 1-1  
Performance 1-1  
Manageability 1-2  
Redundancy 1-3  
VLAN Support 1-4  
Security 1-4  
Quality of Service and Class of Service 1-5  
Monitoring 1-5  
Management Options 1-6  
Management Interface Options 1-6  
Network Configuration Examples 1-7  
Where to Go Next 1-8  
CHAPTER  
2
Using the Command-Line Interface 2-1  
Cisco IOS Command Modes 2-1  
Getting Help 2-3  
Abbreviating Commands 2-4  
Using no and default Forms of Commands 2-4  
Understanding CLI Messages 2-5  
Using Command History 2-5  
Changing the Command History Buffer Size 2-5  
Recalling Commands 2-6  
Disabling the Command History Feature 2-6  
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Using Editing Features 2-6  
Enabling and Disabling Editing Features 2-6  
Editing Commands through Keystrokes 2-7  
Editing Command Lines that Wrap 2-8  
Searching and Filtering Output of show and more Commands 2-9  
Accessing the CLI 2-9  
CHAPTER  
3
Assigning the Switch IP Address and Default Gateway 3-1  
Understanding the Boot Process 3-1  
Assigning Switch Information 3-2  
Default Switch Information 3-2  
Manually Assigning IP Information 3-3  
Checking and Saving the Running Configuration 3-4  
Modifying the Startup Configuration 3-6  
Default Boot Configuration 3-7  
Specifying the Filename to Read and Write the System Configuration 3-7  
Booting a Specific Software Image 3-8  
Controlling Environment Variables 3-8  
Scheduling a Reload of the Software Image 3-11  
Configuring a Scheduled Reload 3-11  
Displaying Scheduled Reload Information 3-12  
CHAPTER  
4
Administering the Switch 4-1  
Managing the System Time and Date 4-1  
Understanding the System Clock 4-1  
Understanding Network Time Protocol 4-2  
Configuring NTP 4-3  
Default NTP Configuration 4-4  
Configuring NTP Authentication 4-4  
Configuring NTP Associations 4-5  
Configuring NTP Broadcast Service 4-6  
Configuring NTP Access Restrictions 4-7  
Configuring the Source IP Address for NTP Packets 4-9  
Displaying the NTP Configuration 4-10  
Configuring Time and Date Manually 4-10  
Setting the System Clock 4-10  
Displaying the Time and Date Configuration 4-11  
Configuring the Time Zone 4-11  
Configuring Summer Time (Daylight Saving Time) 4-12  
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Configuring a System Name and Prompt 4-13  
Default System Name and Prompt Configuration 4-14  
Configuring a System Name 4-14  
Understanding DNS 4-14  
Default DNS Configuration 4-15  
Setting Up DNS 4-15  
Displaying the DNS Configuration 4-16  
Creating a Banner 4-16  
Default Banner Configuration 4-16  
Configuring a Message-of-the-Day Login Banner 4-16  
Configuring a Login Banner 4-18  
Managing the MAC Address Table 4-18  
Building the Address Table 4-19  
MAC Addresses and VLANs 4-19  
Default MAC Address Table Configuration 4-20  
Changing the Address Aging Time 4-20  
Removing Dynamic Address Entries 4-20  
Configuring MAC Address Notification Traps 4-21  
Adding and Removing Static Address Entries 4-23  
Displaying Address Table Entries 4-24  
Managing the ARP Table 4-24  
CHAPTER  
5
Configuring Switch-Based Authentication 5-1  
Preventing Unauthorized Access to Your Switch 5-1  
Protecting Access to Privileged EXEC Commands 5-2  
Default Password and Privilege Level Configuration 5-2  
Setting or Changing a Static Enable Password 5-3  
Protecting Enable and Enable Secret Passwords with Encryption 5-4  
Setting a Telnet Password for a Terminal Line 5-5  
Configuring Username and Password Pairs 5-6  
Configuring Multiple Privilege Levels 5-6  
Setting the Privilege Level for a Command 5-7  
Changing the Default Privilege Level for Lines 5-8  
Logging into and Exiting a Privilege Level 5-8  
Controlling Switch Access with TACACS+ 5-9  
Understanding TACACS+ 5-9  
TACACS+ Operation 5-11  
Configuring TACACS+ 5-11  
Default TACACS+ Configuration 5-12  
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Identifying the TACACS+ Server Host and Setting the Authentication Key 5-12  
Configuring TACACS+ Login Authentication 5-13  
Configuring TACACS+ Authorization for Privileged EXEC Access and Network Services 5-15  
Starting TACACS+ Accounting 5-16  
Displaying the TACACS+ Configuration 5-16  
Controlling Switch Access with RADIUS 5-16  
Understanding RADIUS 5-17  
RADIUS Operation 5-18  
Configuring RADIUS 5-19  
Default RADIUS Configuration 5-19  
Identifying the RADIUS Server Host 5-19  
Configuring RADIUS Login Authentication 5-22  
Defining AAA Server Groups 5-24  
Configuring RADIUS Authorization for User Privileged Access and Network Services 5-26  
Starting RADIUS Accounting 5-27  
Configuring Settings for All RADIUS Servers 5-28  
Configuring the Switch to Use Vendor-Specific RADIUS Attributes 5-28  
Configuring the Switch for Vendor-Proprietary RADIUS Server Communication 5-29  
Displaying the RADIUS Configuration 5-30  
Configuring the Switch for Local Authentication and Authorization 5-31  
Configuring the Switch for Secure Shell 5-32  
Understanding SSH 5-32  
SSH Servers, Integrated Clients, and Supported Versions 5-32  
Limitations 5-33  
Configuring SSH 5-33  
Configuration Guidelines 5-33  
Cryptographic Software Image Guidelines 5-34  
Setting Up the Switch to Run SSH 5-34  
Configuring the SSH Server 5-35  
Displaying the SSH Configuration and Status 5-36  
CHAPTER  
6
Configuring IEEE 802.1x Port-Based Authentication 6-1  
Understanding IEEE 802.1x Port-Based Authentication 6-1  
Device Roles 6-2  
Authentication Initiation and Message Exchange 6-3  
Ports in Authorized and Unauthorized States 6-4  
IEEE 802.1x Accounting 6-5  
IEEE 802.1x Accounting Attribute-Value Pairs 6-5  
IEEE 802.1x Host Mode 6-6  
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Using IEEE 802.1x with Port Security 6-7  
Using IEEE 802.1x with Voice VLAN Ports 6-8  
Using IEEE 802.1x with VLAN Assignment 6-8  
Using IEEE 802.1x with Guest VLAN 6-9  
Using IEEE 802.1x with Wake-on-LAN 6-10  
Unidirectional State 6-10  
Bidirectional State 6-10  
Configuring IEEE 802.1x Authentication 6-11  
Default IEEE 802.1x Configuration 6-11  
IEEE 802.1x Configuration Guidelines 6-12  
Enabling IEEE 802.1x Authentication 6-13  
Configuring the Switch-to-RADIUS-Server Communication 6-14  
Configuring IEEE 802.1x Authentication Using a RADIUS Server 6-16  
Enabling Periodic Re-Authentication 6-16  
Manually Re-Authenticating a Client Connected to a Port 6-17  
Changing the Quiet Period 6-17  
Changing the Switch-to-Client Retransmission Time 6-18  
Setting the Switch-to-Client Frame-Retransmission Number 6-19  
Configuring the Host Mode 6-20  
Configuring a Guest VLAN 6-20  
Resetting the IEEE 802.1x Configuration to the Default Values 6-22  
Configuring IEEE 802.1x Authentication 6-22  
Configuring IEEE 802.1x Accounting 6-24  
Displaying IEEE 802.1x Statistics and Status 6-25  
CHAPTER  
7
Configuring Interface Characteristics 7-1  
Understanding Interface Types 7-1  
Access Ports 7-2  
Trunk Ports 7-2  
Port-Based VLANs 7-3  
EtherChannel Port Groups 7-3  
Connecting Interfaces 7-4  
Using the Interface Command 7-4  
Procedures for Configuring Interfaces 7-5  
Configuring a Range of Interfaces 7-6  
Configuring and Using Interface-Range Macros 7-7  
Configuring Ethernet Interfaces 7-9  
Default Ethernet Interface Configuration 7-9  
Configuring Interface Speed and Duplex Mode 7-10  
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Configuration Guidelines 7-11  
Setting the Interface Speed and Duplex Parameters 7-11  
Adding a Description for an Interface 7-12  
Monitoring and Maintaining the Interfaces 7-13  
Monitoring Interface and Controller Status 7-13  
Clearing and Resetting Interfaces and Counters 7-15  
Shutting Down and Restarting the Interface 7-15  
CHAPTER  
8
Configuring Smartports Macros 8-1  
Understanding Smartports Macros 8-1  
Configuring Smartports Macros 8-2  
Default Smartports Macro Configuration 8-2  
Smartports Macro Configuration Guidelines 8-2  
Creating Smartports Macros 8-4  
Applying Smartports Macros 8-5  
Applying Cisco-Default Smartports Macros 8-6  
Displaying Smartports Macros 8-8  
CHAPTER  
9
Configuring STP 9-1  
Understanding Spanning-Tree Features 9-1  
STP Overview 9-2  
Spanning-Tree Topology and BPDUs 9-3  
Bridge ID, Switch Priority, and Extended System ID 9-4  
Spanning-Tree Interface States 9-4  
Blocking State 9-5  
Listening State 9-6  
Learning State 9-6  
Forwarding State 9-6  
Disabled State 9-7  
How a Switch or Port Becomes the Root Switch or Root Port 9-7  
Spanning Tree and Redundant Connectivity 9-8  
Spanning-Tree Address Management 9-8  
Accelerated Aging to Retain Connectivity 9-8  
Spanning-Tree Modes and Protocols 9-9  
Supported Spanning-Tree Instances 9-9  
Spanning-Tree Interoperability and Backward Compatibility 9-10  
STP and IEEE 802.1Q Trunks 9-10  
Spanning Tree Considerations for Cisco Systems Intelligent Gigabit Ethernet Switch Modules 9-11  
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Configuring Spanning-Tree Features 9-11  
Default Spanning-Tree Configuration 9-12  
Spanning-Tree Configuration Guidelines 9-12  
Changing the Spanning-Tree Mode 9-13  
Disabling Spanning Tree 9-14  
Configuring the Root Switch 9-15  
Configuring a Secondary Root Switch 9-17  
Configuring the Port Priority 9-17  
Configuring the Path Cost 9-19  
Configuring the Switch Priority of a VLAN 9-20  
Configuring Spanning-Tree Timers 9-21  
Configuring the Hello Time 9-21  
Configuring the Forwarding-Delay Time for a VLAN 9-22  
Configuring the Maximum-Aging Time for a VLAN 9-22  
Displaying the Spanning-Tree Status 9-23  
CHAPTER 10  
Configuring MSTP 10-1  
Understanding MSTP 10-2  
Multiple Spanning-Tree Regions 10-2  
IST, CIST, and CST 10-2  
Operations Within an MST Region 10-3  
Hop Count 10-4  
Interoperability with IEEE 802.1D STP 10-4  
Understanding RSTP 10-5  
Port Roles and the Active Topology 10-5  
Rapid Convergence 10-6  
Synchronization of Port Roles 10-7  
Bridge Protocol Data Unit Format and Processing 10-8  
Processing Superior BPDU Information 10-9  
Processing Inferior BPDU Information 10-9  
Topology Changes 10-9  
Configuring MSTP Features 10-10  
Default MSTP Configuration 10-11  
MSTP Configuration Guidelines 10-11  
Specifying the MST Region Configuration and Enabling MSTP 10-12  
Configuring the Root Switch 10-13  
Configuring a Secondary Root Switch 10-15  
Configuring the Port Priority 10-15  
Configuring the Path Cost 10-17  
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Contents  
Configuring the Switch Priority 10-18  
Configuring the Hello Time 10-18  
Configuring the Forwarding-Delay Time 10-19  
Configuring the Maximum-Aging Time 10-20  
Configuring the Maximum-Hop Count 10-20  
Specifying the Link Type to Ensure Rapid Transitions 10-21  
Restarting the Protocol Migration Process 10-21  
Displaying the MST Configuration and Status 10-22  
CHAPTER 11  
Configuring Optional Spanning-Tree Features 11-1  
Understanding Optional Spanning-Tree Features 11-1  
Understanding Port Fast 11-2  
Understanding BPDU Guard 11-3  
Understanding BPDU Filtering 11-3  
Understanding UplinkFast 11-4  
Understanding BackboneFast 11-5  
Understanding EtherChannel Guard 11-8  
Understanding Root Guard 11-8  
Understanding Loop Guard 11-9  
Configuring Optional Spanning-Tree Features 11-9  
Default Optional Spanning-Tree Configuration 11-10  
Optional Spanning-Tree Configuration Guidelines 11-10  
Enabling Port Fast 11-10  
Enabling BPDU Guard 11-11  
Enabling BPDU Filtering 11-12  
Enabling UplinkFast for Use with Redundant Links 11-13  
Enabling BackboneFast 11-14  
Enabling EtherChannel Guard 11-15  
Enabling Root Guard 11-15  
Enabling Loop Guard 11-16  
Displaying the Spanning-Tree Status 11-17  
CHAPTER 12  
Configuring VLANs 12-1  
Understanding VLANs 12-1  
Supported VLANs 12-2  
VLAN Port Membership Modes 12-3  
Configuring Normal-Range VLANs 12-4  
Token Ring VLANs 12-5  
Normal-Range VLAN Configuration Guidelines 12-5  
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VLAN Configuration Mode Options 12-6  
VLAN Configuration in config-vlan Mode 12-6  
VLAN Configuration in VLAN Configuration Mode 12-6  
Saving VLAN Configuration 12-7  
Default Ethernet VLAN Configuration 12-7  
Creating or Modifying an Ethernet VLAN 12-8  
Deleting a VLAN 12-10  
Assigning Static-Access Ports to a VLAN 12-10  
Configuring Extended-Range VLANs 12-11  
Default VLAN Configuration 12-12  
Extended-Range VLAN Configuration Guidelines 12-12  
Creating an Extended-Range VLAN 12-12  
Displaying VLANs 12-13  
Configuring VLAN Trunks 12-14  
Trunking Overview 12-14  
IEEE 802.1Q Configuration Considerations 12-16  
Default Layer 2 Ethernet Interface VLAN Configuration 12-17  
Configuring an Ethernet Interface as a Trunk Port 12-17  
Interaction with Other Features 12-18  
Configuring a Trunk Port 12-18  
Defining the Allowed VLANs on a Trunk 12-19  
Changing the Pruning-Eligible List 12-20  
Configuring the Native VLAN for Untagged Traffic 12-21  
Load Sharing Using STP 12-22  
Load Sharing Using STP Port Priorities 12-22  
Load Sharing Using STP Path Cost 12-24  
Configuring VMPS 12-25  
Understanding VMPS 12-26  
Dynamic Port VLAN Membership 12-26  
VMPS Database Configuration File 12-27  
Default VMPS Client Configuration 12-27  
VMPS Configuration Guidelines 12-27  
Configuring the VMPS Client 12-28  
Entering the IP Address of the VMPS 12-28  
Configuring Dynamic Access Ports on VMPS Clients 12-28  
Reconfirming VLAN Memberships 12-29  
Changing the Reconfirmation Interval 12-30  
Changing the Retry Count 12-30  
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Monitoring the VMPS 12-30  
Troubleshooting Dynamic Port VLAN Membership 12-31  
VMPS Configuration Example 12-31  
CHAPTER 13  
Configuring VTP 13-1  
Understanding VTP 13-1  
The VTP Domain 13-2  
VTP Modes 13-3  
VTP Advertisements 13-3  
VTP Version 2 13-4  
VTP Pruning 13-4  
Configuring VTP 13-6  
Default VTP Configuration 13-6  
VTP Configuration Options 13-7  
VTP Configuration in Global Configuration Mode 13-7  
VTP Configuration in VLAN Configuration Mode 13-7  
VTP Configuration Guidelines 13-8  
Domain Names 13-8  
Passwords 13-8  
VTP Version 13-8  
Configuration Requirements 13-9  
Configuring a VTP Server 13-9  
Configuring a VTP Client 13-10  
Disabling VTP (VTP Transparent Mode) 13-11  
Enabling VTP Version 2 13-12  
Enabling VTP Pruning 13-13  
Adding a VTP Client Switch to a VTP Domain 13-14  
Monitoring VTP 13-15  
CHAPTER 14  
Configuring IGMP Snooping and MVR 14-1  
Understanding IGMP Snooping 14-2  
IGMP Versions 14-2  
Joining a Multicast Group 14-3  
Leaving a Multicast Group 14-5  
Immediate-Leave Processing 14-6  
IGMP Configurable-Leave Timer 14-6  
IGMP Report Suppression 14-6  
Source-Only Networks 14-7  
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Configuring IGMP Snooping 14-7  
Default IGMP Snooping Configuration 14-8  
Enabling or Disabling IGMP Snooping 14-8  
Setting the Snooping Method 14-9  
Configuring a Multicast Router Port 14-10  
Configuring a Host Statically to Join a Group 14-10  
Enabling IGMP Immediate-Leave Processing 14-11  
Configuring the IGMP Leave Timer 14-12  
Disabling IGMP Report Suppression 14-12  
Disabling IP Multicast-Source-Only Learning 14-13  
Configuring the Aging Time 14-14  
Displaying IGMP Snooping Information 14-14  
Understanding Multicast VLAN Registration 14-15  
Using MVR in a Multicast Television Application 14-16  
Configuring MVR 14-17  
Default MVR Configuration 14-18  
MVR Configuration Guidelines and Limitations 14-18  
Configuring MVR Global Parameters 14-18  
Configuring MVR Interfaces 14-20  
Displaying MVR Information 14-21  
Configuring IGMP Filtering and Throttling 14-21  
Default IGMP Filtering and Throttling Configuration 14-22  
Configuring IGMP Profiles 14-23  
Applying IGMP Profiles 14-24  
Setting the Maximum Number of IGMP Groups 14-25  
Configuring the IGMP Throttling Action 14-25  
Displaying IGMP Filtering and Throttling Configuration 14-27  
CHAPTER 15  
Configuring Port-Based Traffic Control 15-1  
Configuring Storm Control 15-1  
Understanding Storm Control 15-1  
Default Storm Control Configuration 15-2  
Configuring Storm Control and Threshold Levels 15-2  
Configuring Protected Ports 15-3  
Configuring Port Security 15-4  
Understanding Port Security 15-4  
Secure MAC Addresses 15-5  
Security Violations 15-5  
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Default Port Security Configuration 15-6  
Port Security Configuration Guidelines 15-6  
Enabling and Configuring Port Security 15-7  
Enabling and Configuring Port Security Aging 15-9  
Displaying Port-Based Traffic Control Settings 15-11  
CHAPTER 16  
Configuring UDLD 16-1  
Understanding UDLD 16-1  
Modes of Operation 16-1  
Methods to Detect Unidirectional Links 16-2  
Configuring UDLD 16-4  
Default UDLD Configuration 16-4  
Configuration Guidelines 16-4  
Enabling UDLD Globally 16-5  
Enabling UDLD on an Interface 16-6  
Resetting an Interface Shut Down by UDLD 16-6  
Displaying UDLD Status 16-7  
CHAPTER 17  
Configuring CDP 17-1  
Understanding CDP 17-1  
Configuring CDP 17-2  
Default CDP Configuration 17-2  
Configuring the CDP Characteristics 17-2  
Disabling and Enabling CDP 17-3  
Disabling and Enabling CDP on an Interface 17-4  
Monitoring and Maintaining CDP 17-5  
CHAPTER 18  
Configuring SPAN and RSPAN 18-1  
Understanding SPAN and RSPAN 18-1  
SPAN and RSPAN Concepts and Terminology 18-3  
SPAN Session 18-3  
Traffic Types 18-3  
Source Port 18-4  
Destination Port 18-4  
Reflector Port 18-5  
SPAN Traffic 18-5  
SPAN and RSPAN Interaction with Other Features 18-6  
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SPAN and RSPAN Session Limits 18-7  
Default SPAN and RSPAN Configuration 18-7  
Configuring SPAN 18-7  
SPAN Configuration Guidelines 18-7  
Creating a SPAN Session and Specifying Ports to Monitor 18-8  
Creating a SPAN Session and Enabling Ingress Traffic 18-9  
Removing Ports from a SPAN Session 18-11  
Configuring RSPAN 18-12  
RSPAN Configuration Guidelines 18-12  
Configuring a VLAN as an RSPAN VLAN 18-13  
Creating an RSPAN Source Session 18-14  
Creating an RSPAN Destination Session 18-15  
Removing Ports from an RSPAN Session 18-16  
Displaying SPAN and RSPAN Status 18-17  
CHAPTER 19  
Configuring RMON 19-1  
Understanding RMON 19-1  
Configuring RMON 19-2  
Default RMON Configuration 19-3  
Configuring RMON Alarms and Events 19-3  
Configuring RMON Collection on an Interface 19-5  
Displaying RMON Status 19-6  
CHAPTER 20  
Configuring System Message Logging 20-1  
Understanding System Message Logging 20-1  
Configuring System Message Logging 20-2  
System Log Message Format 20-2  
Default System Message Logging Configuration 20-3  
Disabling and Enabling Message Logging 20-4  
Setting the Message Display Destination Device 20-4  
Synchronizing Log Messages 20-6  
Enabling and Disabling Timestamps on Log Messages 20-7  
Enabling and Disabling Sequence Numbers in Log Messages 20-8  
Defining the Message Severity Level 20-8  
Limiting Syslog Messages Sent to the History Table and to SNMP 20-10  
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Configuring UNIX Syslog Servers 20-10  
Logging Messages to a UNIX Syslog Daemon 20-11  
Configuring the UNIX System Logging Facility 20-11  
Displaying the Logging Configuration 20-12  
CHAPTER 21  
Configuring SNMP 21-1  
Understanding SNMP 21-1  
SNMP Versions 21-2  
SNMP Manager Functions 21-3  
SNMP Agent Functions 21-3  
SNMP Community Strings 21-4  
Using SNMP to Access MIB Variables 21-4  
SNMP Notifications 21-4  
Configuring SNMP 21-5  
Default SNMP Configuration 21-5  
SNMP Configuration Guidelines 21-6  
Disabling the SNMP Agent 21-6  
Configuring Community Strings 21-7  
Configuring SNMP Groups and Users 21-8  
Configuring SNMP Notifications 21-10  
Setting the Agent Contact and Location Information 21-13  
Limiting TFTP Servers Used Through SNMP 21-13  
SNMP Examples 21-14  
Displaying SNMP Status 21-15  
CHAPTER 22  
Configuring Network Security with ACLs 22-1  
Understanding ACLs 22-2  
Handling Fragmented and Unfragmented Traffic 22-3  
Understanding Access Control Parameters 22-4  
Guidelines for Applying ACLs to Physical Interfaces 22-5  
Configuring ACLs 22-6  
Unsupported Features 22-6  
Creating Standard and Extended IP ACLs 22-7  
ACL Numbers 22-7  
Creating a Numbered Standard ACL 22-8  
Creating a Numbered Extended ACL 22-9  
Creating Named Standard and Extended ACLs 22-12  
Applying Time Ranges to ACLs 22-14  
Including Comments About Entries in ACLs 22-16  
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Creating Named MAC Extended ACLs 22-17  
Creating MAC Access Groups 22-18  
Applying ACLs to Terminal Lines or Physical Interfaces 22-18  
Applying ACLs to a Terminal Line 22-19  
Applying ACLs to a Physical Interface 22-19  
Displaying ACL Information 22-20  
Displaying ACLs 22-20  
Displaying Access Groups 22-21  
Examples for Compiling ACLs 22-22  
Numbered ACL Examples 22-23  
Extended ACL Examples 22-23  
Named ACL Example 22-23  
Commented IP ACL Entry Examples 22-23  
CHAPTER 23  
Configuring QoS 23-1  
Understanding QoS 23-2  
Basic QoS Model 23-3  
Classification 23-4  
Classification Based on QoS ACLs 23-5  
Classification Based on Class Maps and Policy Maps 23-6  
Policing and Marking 23-6  
Mapping Tables 23-7  
Queueing and Scheduling 23-7  
How Class of Service Works 23-7  
Port Priority 23-7  
Port Scheduling 23-8  
Egress CoS Queues 23-8  
Configuring Auto-QoS 23-9  
Generated Auto-QoS Configuration 23-9  
Effects of Auto-QoS on the Configuration 23-11  
Configuration Guidelines 23-11  
Enabling Auto-QoS for VoIP 23-12  
Displaying Auto-QoS Information 23-13  
Auto-QoS Configuration Example 23-14  
Configuring Standard QoS 23-16  
Default Standard QoS Configuration 23-16  
Configuration Guidelines 23-16  
Configuring Classification Using Port Trust States 23-17  
Configuring the Trust State on Ports within the QoS Domain 23-18  
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Configuring the CoS Value for an Interface 23-19  
Configuring Trusted Boundary 23-20  
Enabling Pass-Through Mode 23-22  
Configuring a QoS Policy 23-23  
Classifying Traffic by Using ACLs 23-23  
Classifying Traffic by Using Class Maps 23-27  
Classifying, Policing, and Marking Traffic by Using Policy Maps 23-28  
Configuring CoS Maps 23-31  
Configuring the CoS-to-DSCP Map 23-32  
Configuring the DSCP-to-CoS Map 23-33  
Configuring the Egress Queues 23-34  
Configuring CoS Priority Queues 23-34  
Configuring WRR Priority 23-35  
Enabling the Expedite Queue and Configuring WRR Priority 23-35  
Displaying Standard QoS Information 23-36  
Standard QoS Configuration Examples 23-36  
QoS Configuration for the Existing Wiring Closet 23-37  
QoS Configuration for the Intelligent Wiring Closet 23-38  
CHAPTER 24  
Configuring EtherChannels and Layer 2 Trunk Failover 24-1  
Understanding EtherChannels 24-1  
Understanding Port-Channel Interfaces 24-2  
Understanding the Port Aggregation Protocol and Link Aggregation Protocol 24-3  
PAgP and LACP Modes 24-4  
Physical Learners and Aggregate-Port Learners 24-5  
PAgP and LACP Interaction with Other Features 24-5  
EtherChannel On Mode 24-6  
Understanding Load Balancing and Forwarding Methods 24-6  
Configuring EtherChannels 24-8  
Default EtherChannel Configuration 24-8  
EtherChannel Configuration Guidelines 24-8  
Configuring Layer 2 EtherChannels 24-9  
Configuring EtherChannel Load Balancing 24-11  
Configuring the PAgP Learn Method and Priority 24-12  
Configuring the LACP Port Priority 24-13  
Configuring Hot Standby Ports 24-13  
Configuring the LACP System Priority 24-14  
Displaying EtherChannel, PAgP, and LACP Status 24-15  
Understanding Layer 2 Trunk Failover 24-15  
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Configuring Layer 2 Trunk Failover 24-16  
Default Layer 2 Trunk Failover Configuration 24-16  
Layer 2 Trunk Failover Configuration Guidelines 24-17  
Configuring Layer 2 Trunk Failover 24-17  
Displaying Layer 2 Trunk Failover Status 24-18  
CHAPTER 25  
Troubleshooting 25-1  
Using Recovery Procedures 25-1  
Recovering from a Software Failure 25-1  
Recovering from Lost or Forgotten Passwords 25-2  
Password Recovery with Password Recovery Enabled 25-4  
Procedure with Password Recovery Disabled 25-5  
Preventing Autonegotiation Mismatches 25-7  
SFP Module Security and Identification 25-7  
Diagnosing Connectivity Problems 25-7  
Using Ping 25-8  
Understanding Ping 25-8  
Executing Ping 25-8  
Using Layer 2 Traceroute 25-9  
Understanding Layer 2 Traceroute 25-9  
Usage Guidelines 25-9  
Displaying the Physical Path 25-10  
Using Debug Commands 25-11  
Enabling Debugging on a Specific Feature 25-11  
Enabling All-System Diagnostics 25-12  
Redirecting Debug and Error Message Output 25-12  
Using the debug auto qos Command 25-12  
Using the crashinfo File 25-13  
APPENDIX  
A
B
Supported MIBs A-1  
MIB List A-1  
Using FTP to Access the MIB Files A-3  
APPENDIX  
Working with the Cisco IOS File System, Configuration Files, and Software Images B-1  
Working with the Flash File System B-1  
Displaying Available File Systems B-2  
Setting the Default File System B-3  
Displaying Information about Files on a File System B-3  
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Changing Directories and Displaying the Working Directory B-4  
Creating and Removing Directories B-4  
Copying Files B-5  
Deleting Files B-6  
Creating, Displaying, and Extracting tar Files B-6  
Creating a tar File B-6  
Displaying the Contents of a tar File B-7  
Extracting a tar File B-7  
Displaying the Contents of a File B-8  
Working with Configuration Files B-8  
Guidelines for Creating and Using Configuration Files B-9  
Configuration File Types and Location B-10  
Creating a Configuration File By Using a Text Editor B-10  
Copying Configuration Files By Using TFTP B-10  
Preparing to Download or Upload a Configuration File By Using TFTP B-10  
Downloading the Configuration File By Using TFTP B-11  
Uploading the Configuration File By Using TFTP B-12  
Copying Configuration Files By Using FTP B-12  
Preparing to Download or Upload a Configuration File By Using FTP B-13  
Downloading a Configuration File By Using FTP B-13  
Uploading a Configuration File By Using FTP B-14  
Copying Configuration Files By Using RCP B-15  
Preparing to Download or Upload a Configuration File By Using RCP B-16  
Downloading a Configuration File By Using RCP B-17  
Uploading a Configuration File By Using RCP B-18  
Clearing Configuration Information B-19  
Clearing the Startup Configuration File B-19  
Deleting a Stored Configuration File B-19  
Working with Software Images B-19  
Image Location on the Switch B-20  
tar File Format of Images on a Server or IBM.com B-20  
Copying Image Files By Using TFTP B-21  
Preparing to Download or Upload an Image File By Using TFTP B-21  
Downloading an Image File By Using TFTP B-22  
Uploading an Image File By Using TFTP B-23  
Copying Image Files By Using FTP B-24  
Preparing to Download or Upload an Image File By Using FTP B-24  
Downloading an Image File By Using FTP B-25  
Uploading an Image File By Using FTP B-27  
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Copying Image Files By Using RCP B-28  
Preparing to Download or Upload an Image File By Using RCP B-28  
Downloading an Image File By Using RCP B-29  
Uploading an Image File By Using RCP B-31  
APPENDIX  
C
Getting Help and Technical Assistance C-1  
Before You Call C-1  
Using the Documentation C-2  
Getting Help and Information from the World Wide Web C-2  
Software Service and Support C-2  
Hardware Service and Support C-2  
APPENDIX  
D
Notices D-1  
Edition Notice D-2  
Trademarks D-2  
INDEX  
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Preface  
Audience  
Purpose  
This guide is for the networking professional managing the Cisco Systems Intelligent Gigabit Ethernet  
Switch Modules, hereafter referred to as the switch. Before using this guide, you should have experience  
working with the Cisco IOS and be familiar with the concepts and terminology of Ethernet and local area  
networking.  
This guide provides the information you need to configure software features on your switch.  
Use this guide with other documents for information about these topics:  
•
Requirements—This guide assumes that you have met the hardware and software requirements  
described in the release notes.  
•
Start-up information—This guide assumes that you have assigned switch IP information and  
passwords by using the BladeCenter Management Module WEB page described in the IBM  
BladeCenter QuickStart Guide.  
•
•
Embedded device manager graphical user interface (GUI)—This guide does not provide detailed  
information on the GUI. However, the concepts in this guide are applicable to the GUI user. For  
information about the device manager, see the switch online help.  
CLI command information—This guide provides an overview for using the CLI. For complete  
syntax and usage information about the commands that have been specifically created or changed  
for the switches, see the command reference for this release.  
This guide provides procedures for using the commands that have been created or changed for use with  
the switch. It does not provide detailed information about these commands. For detailed information  
about these commands, see the command reference for this release.  
This guide does not repeat the concepts and CLI procedures provided in the standard Cisco IOS  
Release 12.1 documentation. For information about the standard Cisco IOS Release 12.1 commands, see  
the Cisco IOS documentation set available from the Cisco.com home page at Service and Support >  
Technical Documents. On the Cisco Product Documentation home page, select Release 12.1 from the Cisco  
IOS Software drop-down list.  
This guide does not describe system messages you might encounter or how to install your switch. For  
this information, see the system message guide for this release and to the hardware installation guide.  
For documentation updates, see the release notes for this release.  
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Preface  
Conventions  
Conventions  
This publication uses these conventions to convey instructions and information:  
Command descriptions use these conventions:  
•
•
•
•
•
Commands and keywords are in boldface text.  
Arguments for which you supply values are in italic.  
Square brackets ([ ]) mean optional elements.  
Braces ({ }) group required choices, and vertical bars ( | ) separate the alternative elements.  
Braces and vertical bars within square brackets ([{ | }]) mean a required choice within an optional  
element.  
Interactive examples use these conventions:  
•
•
•
Terminal sessions and system displays are in screenfont.  
Information you enter is in boldface screenfont.  
Nonprinting characters, such as passwords or tabs, are in angle brackets (< >).  
Notes, cautions, and timesavers use these conventions and symbols:  
Note  
Means reader take note. Notes contain helpful suggestions or references to materials not contained in  
this manual.  
Caution  
Means reader be careful. In this situation, you might do something that could result equipment damage  
or loss of data.  
Timesaver  
Means the following will help you solve a problem. The tips information might not be troubleshooting  
or even an action, but could be useful information.  
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Preface  
Related Publications  
Related Publications  
In addition to this document, the following related documentation comes with the Gigabit Ethernet  
switch module:  
•
Cisco Systems Intelligent Gigabit Ethernet Switch Module for the IBM BladeCenter System Release  
Notes  
Note  
Switch requirements and procedures for initial configurations and software upgrades tend to change and  
therefore appear only in the release notes. Before installing, configuring, or upgrading the switch, see  
the release notes for the latest information.  
•
Cisco Systems Intelligent Gigabit Ethernet Switch Module for the IBM BladeCenter System  
Command Reference  
This document is in PDF form on the IBM BladeCenter Documentation CD. It includes:  
–
–
–
–
–
–
–
Command-line interface (CLI) modes  
CLI commands and examples  
Syntax description  
Defaults  
Command history  
Usage guidelines  
Related commands  
•
Cisco Systems Intelligent Gigabit Ethernet Switch Module for the IBM BladeCenter System  
Message Guide  
This document is in PDF on the IBM BladeCenter Documentation CD. It has information about the  
switch-specific system messages. During operation, the system software sends these messages to the  
console or logging server on another system. Not all system messages indicate problems with the  
system. Some messages are informational, and others can help diagnose problems with  
communication lines, internal hardware, or the system software. This document also includes error  
messages that appear when the system fails.  
•
•
Cisco Systems Intelligent Gigabit Ethernet Switch Module for the IBM BladeCenter Installation  
Guide  
This document has installation and configuration instructions for the Gigabit Ethernet switch  
module. This document also provides general information about your Gigabit Ethernet switch  
module, including warranty information and how to get help. This document is also on the IBM  
BladeCenter Documentation CD.  
Cisco Systems Intelligent Gb Fiber Ethernet Switch Module for the IBM BladeCenter Installation  
Guide  
This document has installation and configuration instructions for the Gb Fiber Ethernet switch  
module. This document also provides general information about your Gb Fiber Ethernet switch  
module, including warranty information and how to get help. This document is also on the IBM  
BladeCenter Documentation CD.  
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Preface  
Related Publications  
•
BladeCenter Type 8677 Installation and User’s Guide  
This document is in PDF on the IBM BladeCenter Documentation CD. It contains general  
information about your BladeCenter unit, including:  
–
–
–
–
–
–
Information about features  
How to set up, cable, and start the BladeCenter unit  
How to install options in the BladeCenter unit  
How to configure the BladeCenter unit  
How to perform basic troubleshooting of the BladeCenter unit  
How to get help  
•
BladeCenter Management Module User’s Guide  
This document is in PDF on the IBM BladeCenter Documentation CD. It provides general  
information about the management module, including:  
–
–
–
–
Information about features  
How to start the management module  
How to install the management module  
How to configure and use the management module  
•
BladeCenter HS20 Installation and User’s Guide (for each blade server type)  
These documents are in PDF on the IBM BladeCenter Documentation CD. Each provides general  
information about a blade server, including:  
–
–
–
–
–
–
–
Information about features  
How to set up and start your blade server  
How to install options in your blade server  
How to configure your blade server  
How to install an operating system on your blade server  
How to perform basic troubleshooting of your blade server  
How to get help  
•
•
Cisco IOS Release 12.1 documentation at  
http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/index.html  
Cisco IOS Release 12.2 documentation at  
http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/index.html  
For information about related products, see these documents:  
•
•
Cisco Small Form-Factor Pluggable Modules Installation Notes (order number DOC-7815160=)  
Cisco CWDM GBIC and CWDM SFP Installation Note (not orderable but available on Cisco.com)  
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C H A P T E R  
1
Overview  
This chapter provides these topics about the Cisco Systems Intelligent Gigabit Ethernet Switch Module:  
•
•
•
•
Features, page 1-1  
Management Options, page 1-6  
Network Configuration Examples, page 1-7  
Where to Go Next, page 1-8  
Note  
In this document, IP refers to IP version 4 (IPv4). Layer 3 IP version 6 (IPv6) packets are treated as  
non-IP packets.  
Features  
This section describes the features supported in this release.  
Ease of Use and Ease of Deployment  
•
User-defined Smartports macros for creating custom switch configurations for simplified  
deployment across the network.  
•
Embedded device manager GUI for configuring and monitoring a single switch through a web  
browser. For information about launching the device manager, see the switch hardware installation  
guide. For more information about the device manager, see the switch online help.  
•
Real-time status monitoring of a switch from the LEDs on a front-panel image from the device  
manager.  
Performance  
•
•
•
Autosensing of speed on the 10/100/1000 ports and autonegotiation of duplex mode on the external  
ports for optimizing bandwidth  
Fast EtherChannel and Gigabit EtherChannel for enhanced fault tolerance and for providing up  
to 4 Gbps of bandwidth among switches, routers, and servers  
Support for frame sizes from 64 to 9216 bytes  
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Chapter 1 Overview  
Features  
•
•
Port blocking on forwarding unknown unicast and multicast traffic  
Per-port broadcast storm control for preventing faulty end stations from degrading overall system  
performance with broadcast storms  
•
•
•
•
•
Port Aggregation Protocol (PAgP) and Link Aggregation Control Protocol (LACP) for automatic  
creation of EtherChannel links  
Internet Group Management Protocol (IGMP) snooping for IGMP versions 1, 2, and 3 to limit  
flooding of IP multicast traffic  
IGMP report suppression for sending only one IGMP report per multicast router query to the  
multicast devices (supported only for IGMPv1 or IGMPv2 queries)  
IGMP snooping querier support to configure switch to generate periodic IGMP General Query  
messages  
Multicast VLAN registration (MVR) to continuously send multicast streams in a multicast VLAN  
while isolating the streams from subscriber VLANs for bandwidth and security reasons  
•
•
IGMP filtering for controlling the set of multicast groups to which hosts on a switch port can belong  
IGMP throttling for configuring the action when the maximum number of entries is in the IGMP  
forwarding table  
•
•
Protected port (private VLAN edge port) option for restricting the forwarding of traffic to  
designated ports on the same switch  
Dynamic address learning for enhanced security  
Manageability  
•
Address Resolution Protocol (ARP) for identifying a switch through its IP address and its  
corresponding MAC address  
•
•
Unicast MAC address filtering to drop packets with specific source or destination MAC addresses  
Cisco Discovery Protocol (CDP) versions 1 and 2 for network topology discovery and mapping  
between the switch and other Cisco devices on the network  
•
Network Time Protocol (NTP) for providing a consistent time stamp to all switches from an external  
source  
•
•
Directed unicast requests to a TFTP server for obtaining software upgrades from a TFTP server  
Default configuration storage in flash memory to ensure that the switch can be connected to a  
network and can forward traffic with minimal user intervention  
•
•
•
In-band management access through the embedded device manager through a Netscape Navigator  
or Internet Explorer session  
In-band management access through up to 16 simultaneous Telnet connections for multiple  
command-line interface (CLI)-based sessions over the network  
In-band management access through up to five simultaneous, encrypted Secure Shell (SSH)  
connections for multiple CLI-based sessions over the network (only available in the enhanced  
cryptographic software image)  
•
In-band management access through SNMP versions 1, 2c, and 3 get and set requests  
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Chapter 1 Overview  
Features  
•
Out-of-band management access through the switch service port to a directly-attached terminal or  
to a remote terminal through a serial connection and a modem  
Note  
For additional descriptions of the management interfaces, see the “Management Options”  
section on page 1-6.  
Redundancy  
•
Link state tracking to mirror the state of the external ports on the internal Ethernet links and to allow  
the failover of the processor blade traffic to an operational external link on a separate Cisco Ethernet  
switch  
•
•
HSRP for command-switch redundancy  
UniDirectional Link Detection (UDLD) on all Ethernet ports for detecting and disabling  
unidirectional links on fiber-optic interfaces caused by incorrect fiber-optic wiring or port faults  
•
IEEE 802.1D Spanning Tree Protocol (STP) for redundant backbone connections and loop-free  
networks.  
–
–
–
–
Up to 64 spanning-tree instances supported  
Per-VLAN spanning-tree plus (PVST+) for load balancing across VLANs  
Rapid PVST+ for load balancing across VLANs  
UplinkFast and BackboneFast for fast convergence after a spanning-tree topology change and  
for achieving load balancing among redundant uplinks, including Gigabit uplinks  
•
•
IEEE 802.1s Multiple Spanning Tree Protocol (MSTP) for grouping VLANs into a spanning-tree  
instance and for providing multiple forwarding paths for data traffic and load balancing and rapid  
per-VLAN Spanning-Tree plus (rapid-PVST+), based on the IEEE 802.1w Rapid Spanning Tree  
Protocol (RSTP) for rapid convergence of the spanning tree by immediately transitioning root and  
designated ports to the forwarding state  
Optional spanning-tree features available in the PVST+, rapid PVST+, and MSTP modes:  
–
Port Fast for eliminating the forwarding delay by enabling a port to immediately transition from  
the blocking state to the forwarding state  
–
–
–
BPDU guard for shutting down Port Fast-enabled ports that receive BPDUs  
BPDU filtering for preventing a Port Fast-enabled port from sending or receiving BPDUs  
Root guard for preventing switches outside the network core from becoming the spanning-tree  
root  
–
Loop guard for preventing alternate or root ports from becoming designated ports because of a  
failure that leads to a unidirectional link  
Note  
The switch supports up to 64 spanning-tree instances.  
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Chapter 1 Overview  
Features  
VLAN Support  
•
•
•
The switches support 250 port-based VLANs for assigning users to VLANs associated with  
appropriate network resources, traffic patterns, and bandwidth  
The switch supports up to 4094 VLAN IDs to allow service provider networks to support the number of  
VLANs allowed by the IEEE 802.1Q standard  
IEEE 802.1Q trunking protocol on all ports for network moves, adds, and changes; management and  
control of broadcast and multicast traffic; and network security by establishing VLAN groups for  
high-security users and network resources  
•
•
VLAN Membership Policy Server (VMPS) for dynamic VLAN membership  
VLAN Trunking Protocol (VTP) pruning for reducing network traffic by restricting flooded traffic  
to links destined for stations receiving the traffic  
•
•
Dynamic Trunking Protocol (DTP) for negotiating trunking on a link between two devices and for  
negotiating the type of trunking encapsulation (IEEE 802.1Q) to be used  
VLAN 1 minimization to reduce the risk of spanning-tree loops or storms by allowing VLAN 1 to  
be disabled on any individual VLAN trunk link. With this feature enabled, no user traffic is sent or  
received. The switch CPU continues to send and receive control protocol frames.  
•
Multiple management interface support allowing multiple interfaces to be assigned to a unique IP  
address.  
Security  
•
Bridge protocol data unit (BPDU) guard for shutting down a Port Fast-configured port when an  
invalid configuration occurs  
•
•
Protected port option for restricting the forwarding of traffic to designated ports on the same switch  
Password-protected access (read-only and read-write access) to management interfaces (device  
manager and CLI) for protection against unauthorized configuration changes  
•
Port security option for limiting and identifying MAC addresses of the stations allowed to access  
the port  
•
•
•
Port security aging to set the aging time for secure addresses on a port  
Multilevel security for a choice of security level, notification, and resulting actions  
MAC-based port-level security for restricting the use of a switch port to a specific group of source  
addresses and preventing switch access from unauthorized stations  
•
•
TACACS+, a proprietary feature for managing network security through a TACACS server  
IEEE 802.1x port-based authentication to prevent unauthorized devices from gaining access to the  
network  
•
•
IEEE 802.1x accounting to track network usage  
IEEE 802.1x with wake-on-LAN to allow dormant PCs to be powered on based on the receipt of a  
specific Ethernet frame  
•
Standard and extended IP access control lists (ACLs) for defining security policies  
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Chapter 1 Overview  
Features  
Quality of Service and Class of Service  
•
Automatic quality of service (auto-QoS) to simplify the deployment of existing QoS features by  
classifying traffic and configuring egress queues  
•
IEEE 802.1p class of service (CoS) with eight priority queues on the Gigabit ports for prioritizing  
mission-critical and time-sensitive traffic from data, voice, and telephony applications  
–
IP Differentiated Services Code Point (IP DSCP) and CoS marking priorities on a per-port basis  
for protecting the performance of mission-critical applications  
–
Flow-based packet classification (classification based on information in the MAC, IP, and  
TCP/UDP headers) for high-performance quality of service at the network edge, allowing for  
differentiated service levels for different types of network traffic and for prioritizing  
mission-critical traffic in the network  
–
–
Support for IEEE 802.1p CoS scheduling for classification and preferential treatment of  
high-priority voice traffic  
Trusted boundary (detect the presence of a Cisco IP Phone, trust the CoS value received, and  
ensure port security. If the IP phone is not detected, disable the trusted setting on the port and  
prevent misuse of a high-priority queue.)  
•
Policing  
–
–
–
–
Traffic-policing policies on the switch port for allocating the amount of the port bandwidth to  
a specific traffic flow  
Policing traffic flows to restrict specific applications or traffic flows to metered, predefined  
rates  
Up to 60 policers on ingress Gigabit-capable Ethernet ports  
Granularity of 8 Mbps on 10/100/1000 ports  
Out-of-profile markdown for packets that exceed bandwidth utilization limits  
•
•
Egress Policing and Scheduling of Egress Queues—Four egress queues on all switch ports. Support  
for strict priority and weighted round-robin (WRR) CoS policies  
Source IP/Destination IP (SIP/DIP) address routing  
Monitoring  
•
•
Switch LEDs that show port and switch status  
Switched Port Analyzer (SPAN) and Remote SPAN (RSPAN) for traffic monitoring on any port or  
VLAN  
•
•
•
SPAN support of Intrusion Detection Systems (IDSs) to monitor, repel, and report network security  
violations  
Four groups (history, statistics, alarms, and events) of embedded remote monitoring (RMON) agents  
for network monitoring and traffic analysis  
MAC address notification for tracking the MAC addresses that the switch has learned or removed  
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Chapter 1 Overview  
Management Options  
•
•
Syslog facility for logging system messages about authentication or authorization errors, resource  
issues, and time-out events  
Layer 2 traceroute to identify the physical path that a packet takes from a source device to a  
destination device  
Management Options  
The switch is designed for plug-and-play operation: you only need to assign basic IP information to the  
switch and connect it to the other devices in your network. If you have specific network needs, you can  
configure and monitor the switch—on an individual basis—through its various management interfaces.  
Note  
For information about assigning an IP address by using the BladeCenter Management Module WEB  
page, see the IBM BladeCenter QuickStart Guide.  
Management Interface Options  
You can configure and monitor individual switches by using these interfaces:  
•
An embedded device manager—The device manager is a GUI that is integrated in the software  
image. You use it to can configure and to monitor a single switch through a web browser. For more  
information about the device manager, see the switch online help.  
•
CLI—The switch Cisco IOS software supports desktop-switching features. You can access the CLI  
either by connecting your management station directly to the switch service port or by using Telnet  
or SSH from a remote management station.  
For more information about the CLI, see Chapter 2, “Using the Command-Line Interface.”  
•
SNMP—SNMP provides a means to monitor and control the switch. You can manage switch  
configuration settings, performance, and security and collect statistics by using SNMP management  
applications such as CiscoWorks2000 LAN Management Suite (LMS) and HP OpenView.  
You can manage the switch from an SNMP-compatible management station that is running  
platforms such as HP OpenView or SunNet Manager. The switch supports a comprehensive set of  
MIB extensions and four RMON groups.  
For more information about using SNMP, see the Chapter 21, “Configuring SNMP.”  
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Chapter 1 Overview  
Network Configuration Examples  
Network Configuration Examples  
Figure 1-1, Figure 1-2, and Figure 1-3 show three different network configurations.  
Figure 1-1  
Basic Configuration  
For example,  
Catalyst 3750  
Switch  
Cisco  
ESM  
Firewall  
Network  
BladeCenter  
Figure 1-2  
Trunking Configuration  
Etherchannel  
For example,  
Catalyst 3750  
Switch  
Firewall  
Cisco  
ESM  
Network  
Ports  
17–20  
BladeCenter  
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Chapter 1 Overview  
Where to Go Next  
Figure 1-3  
Redundancy Configuration  
For example,  
Catalyst 3750  
Switch  
Firewall  
Cisco  
ESM  
Network  
Ports  
17–20  
BladeCenter  
Where to Go Next  
Before configuring the switch, review these sections for start-up information:  
•
•
Chapter 2, “Using the Command-Line Interface”  
Chapter 3, “Assigning the Switch IP Address and Default Gateway”  
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C H A P T E R  
2
Using the Command-Line Interface  
This chapter describes the Cisco IOS command-line interface (CLI) that you can use to configure your  
Cisco Systems Intelligent Gigabit Ethernet Switch Module. It contains these sections:  
•
•
•
•
•
•
•
•
•
Cisco IOS Command Modes, page 2-1  
Getting Help, page 2-3  
Abbreviating Commands, page 2-4  
Using no and default Forms of Commands, page 2-4  
Understanding CLI Messages, page 2-5  
Using Command History, page 2-5  
Using Editing Features, page 2-6  
Searching and Filtering Output of show and more Commands, page 2-9  
Accessing the CLI, page 2-9  
Cisco IOS Command Modes  
The user interface is divided into many different modes. The commands available to you depend on  
which mode you are currently in. Enter a question mark (?) at the system prompt to obtain a list of  
commands available for each command mode.  
When you start a session on the switch, you begin in user mode, often called user EXEC mode. Only a  
limited subset of the commands are available in user EXEC mode. For example, most of the user EXEC  
commands are one-time commands, such as show commands, which show the current configuration  
status, and clear commands, which clear counters or interfaces. The user EXEC commands are not saved  
when the switch reboots.  
To have access to all commands, you must enter privileged EXEC mode. Normally, you must enter a  
password to enter privileged EXEC mode. From this mode, you can enter any privileged EXEC  
command or enter global configuration mode.  
Using the configuration modes (global, interface, and line), you can make changes to the running  
configuration. If you save the configuration, these commands are stored and used when the switch  
reboots. To access the various configuration modes, you must start at global configuration mode. From  
global configuration mode, you can enter interface configuration mode and line configuration mode.  
For information on accessing the CLI through the switch service port or through a Telnet session, see  
the hardware installation guide.  
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Chapter 2 Using the Command-Line Interface  
Cisco IOS Command Modes  
Table 2-1 describes the main command modes, how to access each one, the prompt you see in that mode, and  
how to exit the mode. The examples in the table use the host name Switch.  
Table 2-1  
Command Mode Summary  
Mode  
Access Method  
Prompt  
Exit Method  
About This Mode  
Switch>  
User EXEC  
Begin a session with  
your switch.  
Enter logout or quit. Use this mode to  
•
Change terminal  
settings.  
•
•
Perform basic tests.  
Display system  
information.  
Switch#  
Privileged EXEC  
While in user EXEC  
mode, enter the  
Enter disable to exit. Use this mode to verify  
commands that you have  
enable command.  
entered. Use a password to  
protect access to this mode.  
Switch(config)#  
Switch(config-vlan)#  
Global configuration While in privileged  
EXEC mode, enter  
To exit to privileged Use this mode to configure  
EXEC mode, enter  
parameters that apply to the  
the configure  
command.  
exit or end, or press entire switch.  
Ctrl-Z.  
Config-vlan  
While in global  
configuration mode,  
enter the  
To exit to global  
Use this mode to configure  
configuration mode, VLAN parameters. When  
enter the exit  
command.  
VTP mode is transparent,  
you can create  
vlan vlan-id  
command.  
extended-range VLANs  
(VLAN IDs greater than  
1005) and save  
configurations in the switch  
startup configuration file.  
To return to  
privileged EXEC  
mode, press Ctrl-Z or  
enter end.  
Switch(vlan)#  
VLAN configuration While in privileged  
EXEC mode, enter  
To exit to privileged Use this mode to configure  
EXEC mode, enter  
VLAN parameters for  
VLANs 1 to 1005 in the  
VLAN database.  
the vlan database  
command.  
exit.  
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Chapter 2 Using the Command-Line Interface  
Getting Help  
Table 2-1  
Command Mode Summary (continued)  
Mode  
Access Method  
Prompt  
Exit Method  
About This Mode  
Use this mode to configure  
Switch(config-if)#  
Interface  
While in global  
To exit to global  
configuration  
configuration mode,  
enter the interface  
command (with a  
specific interface).  
configuration mode, parameters for the  
enter exit.  
interfaces.  
To return to  
To configure multiple  
privileged EXEC  
interfaces with the same  
mode, press Ctrl-Z or parameters, see the  
enter end.  
“Configuring a Range of  
Interfaces” section on  
page 7-6.  
Switch(config-line)#  
Line configuration  
While in global  
To exit to global  
Use this mode to configure  
configuration mode,  
specify a line with  
the line vty or line  
console command.  
configuration mode, parameters for the terminal  
enter exit.  
line.  
To return to  
privileged EXEC  
mode, press Ctrl-Z or  
enter end.  
Getting Help  
You can enter a question mark (?) at the system prompt to display a list of commands available for each  
command mode. You can also obtain a list of associated keywords and arguments for any command, as  
shown in Table 2-2.  
Table 2-2  
Help Summary  
Command  
Purpose  
help  
Obtain a brief description of the help system in any command mode.  
Obtain a list of commands that begin with a particular character string.  
For example:  
abbreviated-command-entry?  
Switch# di?  
dir disable disconnect  
abbreviated-command-entry<Tab>  
Complete a partial command name.  
For example:  
Switch# sh conf<tab>  
Switch# show configuration  
?
List all commands available for a particular command mode.  
For example:  
Switch> ?  
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Chapter 2 Using the Command-Line Interface  
Abbreviating Commands  
Table 2-2  
Help Summary (continued)  
Purpose  
Command  
command ?  
List the associated keywords for a command.  
For example:  
Switch> show ?  
command keyword ?  
List the associated arguments for a keyword.  
For example:  
Switch(config)# cdp holdtime ?  
<10-255> Length of time (in sec) that receiver must keep this packet  
Abbreviating Commands  
You have to enter only enough characters for the switch to recognize the command as unique. This  
example shows how to enter the show configuration privileged EXEC command:  
Switch# show conf  
Using no and default Forms of Commands  
Almost every configuration command also has a no form. In general, use the no form to disable a feature  
or function or reverse the action of a command. For example, the no shutdown interface configuration  
command reverses the shutdown of an interface. Use the command without the keyword no to re-enable  
a disabled feature or to enable a feature that is disabled by default.  
Configuration commands can also have a default form. The default form of a command returns the  
command setting to its default. Most commands are disabled by default, so the default form is the same  
as the no form. However, some commands are enabled by default and have variables set to certain  
default values. In these cases, the default command enables the command and sets variables to their  
default values.  
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Chapter 2 Using the Command-Line Interface  
Understanding CLI Messages  
Understanding CLI Messages  
Table 2-3 lists some error messages that you might encounter while using the CLI to configure your  
switch.  
Table 2-3  
Common CLI Error Messages  
Error Message  
Meaning  
How to Get Help  
% Ambiguous command:  
"show con"  
You did not enter enough characters Re-enter the command followed by a question mark (?)  
for your switch to recognize the  
command.  
with a space between the command and the question  
mark.  
The possible keywords that you can enter with the  
command appear.  
% Incomplete command.  
You did not enter all the keywords or Re-enter the command followed by a question mark (?)  
values required by this command.  
with a space between the command and the question  
mark.  
The possible keywords that you can enter with the  
command appear.  
% Invalid input detected  
at ‘^’ marker.  
You entered the command  
incorrectly. The caret (^) marks the that are available in this command mode.  
Enter a question mark (?) to display all the commands  
point of the error.  
The possible keywords that you can enter with the  
command appear.  
Using Command History  
The software provides a history or record of commands that you have entered. This feature is particularly  
useful for recalling long or complex commands or entries, including access lists. You can customize the  
command history feature to suit your needs as described in these sections:  
•
•
•
Changing the Command History Buffer Size, page 2-5  
Recalling Commands, page 2-6  
Disabling the Command History Feature, page 2-6  
Changing the Command History Buffer Size  
By default, the switch records ten command lines in its history buffer. Beginning in privileged EXEC  
mode, enter this command to change the number of command lines that the switch records during the  
current terminal session:  
Switch# terminal history[size number-of-lines]  
The range is from 0 to 256.  
Beginning in line configuration mode, enter this command to configure the number of command lines  
the switch records for all sessions on a particular line:  
Switch(config-line)# history [size number-of-lines]  
The range is from 0 to 256.  
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Chapter 2 Using the Command-Line Interface  
Using Editing Features  
Recalling Commands  
To recall commands from the history buffer, perform one of the actions listed in Table 2-4:  
Table 2-4  
Recalling Commands  
Action1  
Result  
Press Ctrl-P or the up arrow key.  
Recall commands in the history buffer, beginning with the most recent command.  
Repeat the key sequence to recall successively older commands.  
Press Ctrl-N or the down arrow key.  
Return to more recent commands in the history buffer after recalling commands  
with Ctrl-P or the up arrow key. Repeat the key sequence to recall successively  
more recent commands.  
show history  
While in privileged EXEC mode, list the last several commands that you just  
entered. The number of commands that appear is determined by the setting of the  
terminal history global configuration command and history line configuration  
command.  
1. The arrow keys function only on ANSI-compatible terminals such as VT100s.  
Disabling the Command History Feature  
The command history feature is automatically enabled.  
To disable the feature during the current terminal session, enter the terminal no history privileged  
EXEC command.  
To disable command history for the line, enter the no history line configuration command.  
Using Editing Features  
This section describes the editing features that can help you manipulate the command line. It contains  
these sections:  
•
•
•
Enabling and Disabling Editing Features, page 2-6  
Editing Commands through Keystrokes, page 2-7  
Editing Command Lines that Wrap, page 2-8  
Enabling and Disabling Editing Features  
Although enhanced editing mode is automatically enabled, you can disable it.  
To re-enable the enhanced editing mode for the current terminal session, enter this command in  
privileged EXEC mode:  
Switch# terminal editing  
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Chapter 2 Using the Command-Line Interface  
Using Editing Features  
To reconfigure a specific line to have enhanced editing mode, enter this command in line configuration  
mode:  
Switch(config-line)# editing  
To globally disable enhanced editing mode, enter this command in line configuration mode:  
Switch(config-line)# no editing  
Editing Commands through Keystrokes  
Table 2-5 shows the keystrokes that you need to edit command lines.  
Table 2-5  
Editing Commands through Keystrokes  
Capability  
Keystroke1  
Purpose  
Move around the command line to  
make changes or corrections.  
Press Ctrl-B, or press the Move the cursor back one character.  
left arrow key.  
Press Ctrl-F, or press the Move the cursor forward one character.  
right arrow key.  
Press Ctrl-A.  
Press Ctrl-E.  
Press Esc B.  
Press Esc F.  
Press Ctrl-T.  
Move the cursor to the beginning of the command line.  
Move the cursor to the end of the command line.  
Move the cursor back one word.  
Move the cursor forward one word.  
Transpose the character to the left of the cursor with the  
character located at the cursor.  
Recall commands from the buffer and Press Ctrl-Y.  
Recall the most recent entry in the buffer.  
Recall the next buffer entry.  
paste them in the command line. The  
Press Esc Y.  
switch provides a buffer with the last  
ten items that you deleted.  
The buffer contains only the last 10 items that you have  
deleted or cut. If you press Esc Y more than ten times, you  
cycle to the first buffer entry.  
Delete entries if you make a mistake Press the Delete or  
Erase the character to the left of the cursor.  
or change your mind.  
Backspace key.  
Press Ctrl-D.  
Press Ctrl-K.  
Delete the character at the cursor.  
Delete all characters from the cursor to the end of the  
command line.  
Press Ctrl-U or Ctrl-X.  
Delete all characters from the cursor to the beginning of  
the command line.  
Press Ctrl-W.  
Press Esc D.  
Delete the word to the left of the cursor.  
Delete from the cursor to the end of the word.  
Capitalize at the cursor.  
Capitalize or lowercase words or  
capitalize a set of letters.  
Press Esc C.  
Press Esc L.  
Change the word at the cursor to lowercase.  
Capitalize letters from the cursor to the end of the word.  
Press Esc U.  
Designate a particular keystroke as  
an executable command, perhaps as a  
shortcut.  
Press Ctrl-V or Esc Q.  
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Chapter 2 Using the Command-Line Interface  
Using Editing Features  
Table 2-5  
Editing Commands through Keystrokes (continued)  
Capability  
Keystroke1  
Purpose  
Scroll down one line.  
Scroll down a line or screen on  
displays that are longer than the  
terminal screen can display.  
Press the Return key.  
Press the Space bar.  
Scroll down one screen.  
Note  
The More prompt is used for  
any output that has more  
lines than can be displayed  
on the terminal screen,  
including show command  
output. You can use the  
Return and Space bar  
keystrokes whenever you see  
the More prompt.  
Redisplay the current command line Press Ctrl-L or Ctrl-R.  
if the switch suddenly sends a  
Redisplay the current command line.  
message to your screen.  
1. The arrow keys function only on ANSI-compatible terminals such as VT100s.  
Editing Command Lines that Wrap  
You can use a wraparound feature for commands that extend beyond a single line on the screen. When  
the cursor reaches the right margin, the command line shifts ten spaces to the left. You cannot see the  
first ten characters of the line, but you can scroll back and check the syntax at the beginning of the  
command.  
To scroll back to the beginning of the command entry, press Ctrl-B or the left arrow key repeatedly. You  
can also press Ctrl-A to immediately move to the beginning of the line.  
Note  
The arrow keys function only on ANSI-compatible terminals such as VT100s.  
In this example, the access-list global configuration command entry extends beyond one line. When the  
cursor first reaches the end of the line, the line is shifted ten spaces to the left and redisplayed. The dollar  
sign ($) shows that the line has been scrolled to the left. Each time the cursor reaches the end of the line,  
the line is again shifted ten spaces to the left.  
Switch(config)# access-list 101 permit tcp 131.108.2.5 255.255.255.0 131.108.1  
Switch(config)# $ 101 permit tcp 131.108.2.5 255.255.255.0 131.108.1.20 255.25  
Switch(config)# $t tcp 131.108.2.5 255.255.255.0 131.108.1.20 255.255.255.0 eq  
Switch(config)# $108.2.5 255.255.255.0 131.108.1.20 255.255.255.0 eq 45  
After you complete the entry, press Ctrl-A to check the complete syntax before pressing the Return key  
to execute the command. The dollar sign ($) appears at the end of the line to show that the line has been  
scrolled to the right:  
Switch(config)# access-list 101 permit tcp 131.108.2.5 255.255.255.0 131.108.1$  
The software assumes you have a terminal screen that is 80 columns wide. If you have a width other than  
that, use the terminal width privileged EXEC command to set the width of your terminal.  
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Chapter 2 Using the Command-Line Interface  
Searching and Filtering Output of show and more Commands  
Use line wrapping with the command history feature to recall and modify previous complex command  
entries. For information about recalling previous command entries, see the “Editing Commands through  
Keystrokes” section on page 2-7.  
Searching and Filtering Output of show and more Commands  
You can search and filter the output for show and more commands. This is useful when you need to sort  
through large amounts of output or if you want to exclude output that you do not need to see.  
To use this functionality, enter a show or more command followed by the pipe character (|), one of the  
keywords begin, include, or exclude, and an expression that you want to search for or filter out:  
command | {begin | include | exclude} regular-expression  
Expressions are case sensitive. For example, if you enter | exclude output, the lines that contain output  
are not displayed, but the lines that contain Output appear.  
This example shows how to include in the output display only lines where the expression protocol  
appears:  
Switch# show interfaces | include protocol  
Vlan1 is up, line protocol is up  
Vlan10 is up, line protocol is down  
GigabitEthernet0/17 is up, line protocol is down  
GigabitEthernet0/20 is up, line protocol is up  
Accessing the CLI  
Before you can access the CLI, you need to connect a terminal or PC to the switch service port and power  
on the switch as described in the hardware installation guide that shipped with your switch. Then, to  
understand the boot process and the options available for assigning IP information, see Chapter 3,  
“Assigning the Switch IP Address and Default Gateway.”  
If your switch is already configured, you can access the CLI through a local service connection or  
through a remote Telnet session, but your switch must first be configured for this type of access. For  
more information, see the “Setting a Telnet Password for a Terminal Line” section on page 5-5.  
You can establish a connection with the switch by either  
•
Connecting the switch service port to a management station or dial-up modem. For information  
about connecting to the service port, see the switch hardware installation guide.  
•
Using any Telnet TCP/IP or encrypted Secure Shell (SSH) package from a remote management  
station. The switch must have network connectivity with the Telnet or SSH client, and the switch  
must have an enable secret password configured.  
For information about configuring the switch for Telnet access, see the “Setting a Telnet Password  
for a Terminal Line” section on page 5-5. The switch supports up to 16 simultaneous Telnet sessions.  
Changes made by one Telnet user are reflected in all other Telnet sessions.  
For information about configuring the switch for SSH, see the “Configuring the Switch for Secure  
Shell” section on page 5-32. The switch supports up to five simultaneous secure SSH sessions.  
After you connect through the service port, or through a Telnet session, or through an SSH session, the  
user EXEC prompt appears on the management station.  
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Chapter 2 Using the Command-Line Interface  
Accessing the CLI  
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C H A P T E R  
3
Assigning the Switch IP Address and Default  
Gateway  
This chapter describes how to create the initial switch configuration (for example, assign the switch IP  
address and default gateway information) for the Cisco Systems Intelligent Gigabit Ethernet Switch  
Module.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release and the Cisco IOS IP and IP Routing Command Reference, Release 12.1.  
This chapter consists of these sections:  
•
•
•
•
•
Understanding the Boot Process, page 3-1  
Assigning Switch Information, page 3-2  
Checking and Saving the Running Configuration, page 3-4  
Modifying the Startup Configuration, page 3-6  
Scheduling a Reload of the Software Image, page 3-11  
Understanding the Boot Process  
Before you can assign switch information (IP address, subnet mask, default gateway, secret and Telnet  
passwords, and so forth), you need to install and power on the switch as described in the hardware  
installation guide that shipped with your switch.  
The normal boot process involves the operation of the boot loader software, which performs these  
activities:  
•
Performs low-level CPU initialization. It initializes the CPU registers, which control where physical  
memory is mapped, its quantity, its speed, and so forth.  
•
Performs power-on self-test (POST) for the CPU subsystem. It tests the CPU DRAM and the portion  
of the flash device that makes up the flash file system.  
•
•
Initializes the flash file system on the system board.  
Loads a default operating system software image into memory and boots the switch.  
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Chapter 3 Assigning the Switch IP Address and Default Gateway  
Assigning Switch Information  
The boot loader provides access to the flash file system before the operating system is loaded. Normally,  
the boot loader is used only to load, uncompress, and launch the operating system. After the boot loader  
gives the operating system control of the CPU, the boot loader is not active until the next system reset  
or power on.  
The boot loader also provides trap-door access into the system if the operating system has problems so  
serious that it cannot be used. The trap-door mechanism provides enough access to the system so that if  
it is necessary, you can format the flash file system, re-install the operating system software image by  
using the XMODEM Protocol, recover from a lost or forgotten password, and finally restart the  
operating system.  
Assigning Switch Information  
Use the BladeCenter Management Module WEB page to assign IP information to the switch. For more  
information, see the IBM BladeCenter QuickStart Guide.  
If the switch reboots, the switch uses the IP address, subnet mask, and gateway configured in the  
stored-configuration file.  
This section has this configuration information:  
•
•
Default Switch Information, page 3-2  
Manually Assigning IP Information, page 3-3  
Default Switch Information  
Table 3-1 shows the default switch information.  
Table 3-1  
Default Switch Information  
Feature  
Default Setting  
IP address and subnet mask  
10.10.10.9x, where x is the slot number of the switch in  
the BladeCenter chassis.  
Subnet mask  
255.255.255.0.  
Default gateway  
Enable secret password  
Hostname  
No default gateway is defined.  
No password is defined.  
The factory-assigned default host name is Switch.  
USERID. You must use all uppercase letters.  
Telnet username  
Telnet password  
PASSW0RD. (Note that 0 is the number zero. You must  
use all uppercase letters.)  
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Chapter 3 Assigning the Switch IP Address and Default Gateway  
Assigning Switch Information  
Manually Assigning IP Information  
You can configure multiple IP addresses for a switch. Each IP address and its subnet mask must be  
unique and belong to different subnets. You cannot configure IP addresses that cross other subnets on  
the switch. Each IP address must be assigned to a different VLAN interface. The switch can be managed  
from any valid IP address.  
Because the switch is inside the IBM BladeCenter Chassis, you need to consider some special  
circumstances before assigning IP addresses. The chassis management module acts as the IP proxy for  
the switch if the IP address of the switch and the primary VLAN interface is in the same subnet as the  
chassis management module. The chassis management module then carries the switch management  
traffic (SNMP, HTML, FTP, Telnet).  
Because there can be multiple VLAN interfaces on a switch at a given time, you need to designate one  
VLAN interface as the primary VLAN interface. The primary VLAN interface is known as the  
management VLAN. The management VLANs configuration has the keyword management associated  
with it. Only one VLAN interface can be configured as the management VLAN at a given time.  
The management VLAN has special behaviors on the switch. The management VLAN communicates  
with the chassis management module. The management VLAN is always the native VLAN on the  
Ethernet interfaces that directly connect to the chassis management module. When the chassis  
management module assigns an IP address to the switch, the switch applies it to the management VLAN.  
When the switch receives an IP address update request from the chassis management module, the switch  
overwrites any IP address that is configured on the management VLAN interface. The VLAN interface  
configured as the management VLAN cannot be placed into the shutdown state.  
If the switch is managed with a single IP address, we highly recommend that the chassis management  
module assign the IP address to the switch. The switch IP address is configured on the chassis  
management module web page. If the switch is managed by multiple IP addresses, we still recommend  
that the chassis management module assign the IP address to the switch for the management VLAN. Any  
additional IP addresses that you may want must be configured from the CLI.  
Changing the management VLAN does not require modifying the configured IP address even if the IP  
address is assigned by the chassis management module. The IP address of the current management  
VLAN is automatically copied by the switch when the new VLAN interface is created and designated  
as the management VLAN. To change the management VLAN, create an additional VLAN interface,  
and then enter the management command on that VLAN interface. The switch automatically copies the  
IP address.  
Assign additional IP addresses that are needed for switch management to VLAN interfaces other than  
the management VLAN interface.  
Note  
The IP addresses that are assigned to multiple VLAN interfaces must be in different subnets. The switch  
does not allow two or more VLAN interfaces to have IP addresses in the same subnet.  
Beginning in privileged EXEC mode, follow these steps to manually assign IP information to a VLAN  
interface and then to designate that VLAN interface as the management VLAN:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface vlan vlan-id  
Enter interface configuration mode, and enter the VLAN to which the IP  
information is assigned. The range is 1 to 4094.  
Step 3  
ip address ip-address subnet-mask  
Enter the IP address and subnet mask.  
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Checking and Saving the Running Configuration  
Command  
Purpose  
Step 4  
management  
Enable the VLAN interface as the management VLAN.  
Return to global configuration mode.  
Step 5  
Step 6  
Step 7  
Step 8  
Step 9  
exit  
end  
Return to privileged EXEC mode.  
show interfaces vlan vlan-id  
show ip redirects  
Verify the configured IP address.  
Verify the configured default gateway.  
(Optional) Save your entries in the configuration file.  
copy running-config startup-config  
To remove the switch IP address, use the no ip address interface configuration command. If you are  
removing the address through a Telnet session, your connection to the switch will be lost. To remove the  
default gateway address, use the no ip default-gateway global configuration command.  
Note  
The no ip address interface configuration command is not supported on the management VLAN.  
For information on setting the switch system name, protecting access to privileged EXEC commands,  
and setting time and calendar services, see Chapter 4, “Administering the Switch.”  
Checking and Saving the Running Configuration  
You can check the configuration settings you entered or changes that you made by entering the show  
running-config privileged EXEC command:  
Switch# show running-config  
Building configuration...  
Current configuration : 5277 bytes  
!
version 12.1  
no service pad  
service timestamps debug uptime  
service timestamps log uptime  
no service password-encryption  
!
hostname Switch  
!
!
username USERID privilege 15 password 0 PASSW0RD  
username USERID1 privilege 15 password 0 PASSWORD  
ip subnet-zero  
!
vtp mode transparent  
!
spanning-tree mode pvst  
no spanning-tree optimize bpdu transmission  
spanning-tree extend system-id  
!
!
vlan 2  
name operational  
!
interface GigabitEthernet0/1  
description blade1  
switchport access vlan 2  
switchport trunk native vlan 2  
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Checking and Saving the Running Configuration  
switchport trunk allowed vlan 2-4094  
switchport mode trunk  
storm-control broadcast level 99.99 99.98  
spanning-tree bpdufilter enable  
!
interface GigabitEthernet0/2  
description blade2  
switchport access vlan 2  
switchport trunk native vlan 2  
switchport trunk allowed vlan 2-4094  
switchport mode trunk  
ip access-group SecWiz_Gi0_2_in_ip in  
spanning-tree bpdufilter enable  
!
.
.
.
!
interface GigabitEthernet0/15  
description mgmt1  
switchport trunk allowed vlan 1  
switchport mode trunk  
ip access-group SecWiz_Gi0_1_out_ip in  
spanning-tree cost 100  
!
interface GigabitEthernet0/16  
description mgmt2  
switchport trunk allowed vlan 1  
switchport mode trunk  
ip access-group SecWiz_Gi0_1_out_ip in  
spanning-tree cost 100  
!
interface GigabitEthernet0/17  
description extern1  
switchport access vlan 2  
switchport trunk native vlan 2  
ip access-group SecWiz_Gi0_1_out_ip in  
!
interface GigabitEthernet0/18  
description extern2  
switchport access vlan 2  
switchport trunk native vlan 2  
switchport mode access  
ip access-group SecWiz_Gi0_1_out_ip in  
!
interface GigabitEthernet0/19  
description extern3  
switchport access vlan 2  
switchport trunk native vlan 2  
switchport mode access  
ip access-group SecWiz_Gi0_1_out_ip in  
!
interface GigabitEthernet0/20  
description extern4  
switchport access vlan 2  
switchport trunk native vlan 2  
switchport mode access  
ip access-group SecWiz_Gi0_1_out_ip in  
speed 1000  
!
interface Vlan1  
ip address 172.20.138.185 255.255.255.240  
no ip route-cache  
management  
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Chapter 3 Assigning the Switch IP Address and Default Gateway  
Modifying the Startup Configuration  
!
ip default-gateway 172.20.138.178  
ip http server  
!
ip access-list extended SecWiz_Gi0_1_out_ip  
ip access-list extended SecWiz_Gi0_2_in_ip  
deny  
ip any host 1.1.1.1  
permit ip any any  
!
snmp-server community public RO  
snmp-server community private RW  
!
line con 0  
login local  
line vty 0 4  
login local  
line vty 5 15  
login local  
!
end  
To store the configuration or changes you have made to your startup configuration in flash memory, enter  
the copy running-config startup-config privileged EXEC command. This command saves the  
configuration settings that you made. If you fail to do this, your configuration will be lost the next time  
you reload the system. To display information stored in the NVRAM section of flash memory, use the  
show startup-config or more startup-config privileged EXEC command.  
Switch# copy running-config startup-config  
Destination filename [startup-config]?  
Building configuration...  
For more information about alternative locations from which to copy the configuration file, see  
Appendix B, “Working with the Cisco IOS File System, Configuration Files, and Software Images.”  
Modifying the Startup Configuration  
This section describes how to modify the switch startup configuration. It contains this configuration  
information:  
•
•
•
•
Default Boot Configuration, page 3-7  
Specifying the Filename to Read and Write the System Configuration, page 3-7  
Booting a Specific Software Image, page 3-8  
Controlling Environment Variables, page 3-8  
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Modifying the Startup Configuration  
Default Boot Configuration  
Table 3-2 shows the default boot configuration.  
Default Boot Configuration  
Default Setting  
Table 3-2  
Feature  
Operating system software image  
The switch attempts to automatically boot the system using information in the BOOT  
environment variable. If the variable is not set, the switch attempts to load and  
execute the first executable image it can by performing a recursive, depth-first search  
throughout the flash file system.  
The software image is stored in a directory that has the same name as the image file  
(excluding the .bin extension).  
In a depth-first search of a directory, each encountered subdirectory is completely  
searched before continuing the search in the original directory.  
Configuration file  
Configured switches use the config.text file stored on the system board in flash  
memory.  
A new switch has no configuration file.  
Specifying the Filename to Read and Write the System Configuration  
By default, the Cisco IOS software uses the file config.text to read and write a nonvolatile copy of the  
system configuration. However, you can specify a different filename that is loaded during the next boot  
cycle.  
Beginning in privileged EXEC mode, follow these steps to specify a different configuration filename:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
boot config-file flash:/file-url  
Enter global configuration mode.  
Specify the configuration file to load during the next boot cycle.  
For file-url, specify the path (directory) and the configuration  
filename.  
Filenames and directory names are case sensitive.  
Return to privileged EXEC mode.  
Verify your entries.  
Step 3  
Step 4  
end  
show boot  
The boot config-file global configuration command changes the  
setting of the CONFIG_FILE environment variable.  
Step 5  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return to the default setting, use the no boot config-file global configuration command.  
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Chapter 3 Assigning the Switch IP Address and Default Gateway  
Modifying the Startup Configuration  
Booting a Specific Software Image  
By default, the switch attempts to automatically boot the system using information in the BOOT  
environment variable. If this variable is not set, the switch attempts to load and execute the first  
executable image it can by performing a recursive, depth-first search throughout the flash file system. In  
a depth-first search of a directory, each encountered subdirectory is completely searched before  
continuing the search in the original directory. However, you can specify a specific image to boot.  
Beginning in privileged EXEC mode, follow these steps to configure the switch to boot a specific image  
during the next boot cycle:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
boot system filesystem:/file-url  
Configure the switch to boot a specific image in flash memory during the  
next boot cycle.  
•
•
For filesystem:, use flash: for the system board flash device.  
For file-url, specify the path (directory) and the name of the bootable  
image.  
Filenames and directory names are case sensitive.  
Return to privileged EXEC mode.  
Verify your entries.  
Step 3  
Step 4  
end  
show boot  
The boot system global command changes the setting of the BOOT  
environment variable.  
During the next boot cycle, the switch attempts to automatically boot the  
system using information in the BOOT environment variable.  
Step 5  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To return to the default setting, use the no boot system global configuration command.  
Controlling Environment Variables  
With a normally operating switch, you enter the boot loader mode only through a service port connection  
at 9600 bps. Use the BladeCenter management application to restart the switch. When the switch  
restarts, send ESC sequence characters to the service port to stop the autoboot.  
You should then see the boot loader Switch: prompt. The boot loader performs low-level CPU  
initialization, performs POST, and loads a default operating system image into memory.  
The switch boot loader software provides support for nonvolatile environment variables, which can be  
used to control how the boot loader, or any other software running on the system, behaves. Boot loader  
environment variables are similar to environment variables that can be set on UNIX or DOS systems.  
Environment variables that have values are stored in the flash file system in various files as shown in  
Table 3-3.  
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Modifying the Startup Configuration  
Table 3-3  
Environment Variables Storage Location  
Environment Variable  
Location (file system:filename)  
flash:env_vars  
BAUD, ENABLE_BREAK, CONFIG_BUFSIZE,  
CONFIG_FILE, MANUAL_BOOT, PS1  
BOOT, BOOTHLPR, HELPER, HELPER_CONFIG_FILE flash:system_env_vars  
Each line in these files contains an environment variable name and an equal sign followed by the value  
of the variable. A variable has no value if it is not listed in this file; it has a value if it is listed in the file  
even if the value is a null string. A variable that is set to a null string (for example, “ ”) is a variable with  
a value. Many environment variables are predefined and have default values.  
Environment variables store two kinds of data:  
•
Data that controls code, which does not read the Cisco IOS configuration file. For example, the name  
of a boot loader helper file, which extends or patches the functionality of the boot loader can be  
stored as an environment variable.  
•
Data that controls code, which is responsible for reading the Cisco IOS configuration file. For  
example, the name of the Cisco IOS configuration file can be stored as an environment variable.  
You can change the settings of the environment variables by accessing the boot loader or by using Cisco  
IOS commands. It is not necessary to alter the setting of the environment variables.  
Note  
For complete syntax and usage information for the boot loader commands and environment variables,  
see the command reference for this release.  
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Chapter 3 Assigning the Switch IP Address and Default Gateway  
Modifying the Startup Configuration  
Table 3-4 describes the function of the most common environment variables.  
Environment Variables  
Table 3-4  
Variable  
Boot Loader Command  
Cisco IOS Global Configuration Command  
MANUAL_BOOT  
set MANUAL_BOOT yes  
boot manual  
Decides whether the switch automatically or Enables manually booting the switch during  
manually boots.  
the next boot cycle and changes the setting of  
the MANUAL_BOOT environment variable.  
Valid values are 1, yes, 0, and no. If it is set  
to no or 0, the boot loader attempts to  
The next time you reboot the system, the  
automatically boot the system. If it is set to switch is in boot loader mode. To boot the  
anything else, you must manually boot the  
switch from the boot loader mode.  
system, use the boot flash:filesystem:/file-url  
boot loader command, and specify the name  
of the bootable image.  
BOOT  
set BOOT filesystem:/file-url ...  
boot system filesystem:/file-url  
A semicolon-separated list of executable  
files to try to load and execute when  
automatically booting. If the BOOT  
Specifies the software image to load during  
the next boot cycle. This command changes  
the setting of the BOOT environment  
variable.  
environment variable is not set, the system  
attempts to load and execute the first  
executable image it can find by using a  
recursive, depth-first search through the  
flash file system. If the BOOT variable is set  
but the specified images cannot be loaded,  
the system attempts to boot the first bootable  
file that it can find in the flash file system.  
CONFIG_FILE  
set CONFIG_FILE flash:/file-url  
boot config-file flash:/file-url  
Changes the filename that the software uses Specifies the filename that the software uses  
to read and write a nonvolatile copy of the  
system configuration.  
to read and write a nonvolatile copy of the  
system configuration. This command changes  
the CONFIG_FILE environment variable.  
CONFIG_BUFSIZE  
set CONFIG_BUFSIZE size  
boot buffersize size  
Changes the buffer size that the software  
Specifies the size of the file system-simulated  
uses to hold a copy of the configuration file NVRAM in flash memory. The buffer holds a  
in memory. The configuration file cannot be copy of the configuration file in memory. This  
larger than the buffer size allocation. The  
range is from 4096 to 524288 bytes.  
command changes the setting of the  
CONFIG_BUFSIZE environment variable.  
You must reload the switch by using the  
reload privileged EXEC command for this  
command to take effect.  
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Scheduling a Reload of the Software Image  
Scheduling a Reload of the Software Image  
You can schedule a reload of the software image to occur on the switch at a later time (for example, late  
at night or during the weekend when the switch is used less), or you can synchronize a reload  
network-wide (for example, to perform a software upgrade on all switches in the network).  
Note  
A scheduled reload must take place within approximately 24 days.  
Configuring a Scheduled Reload  
To configure your switch to reload the software image at a later time, use one of these commands in  
privileged EXEC mode:  
•
reload in [hh:]mm [text]  
This command schedules a reload of the software to take affect in the specified minutes or hours and  
minutes. The reload must take place within approximately 24 days. You can specify the reason for  
the reload in a string up to 255 characters in length.  
•
reload at hh:mm [month day | day month] [text]  
This command schedules a reload of the software to take place at the specified time (using a 24-hour  
clock). If you specify the month and day, the reload is scheduled to take place at the specified time  
and date. If you do not specify the month and day, the reload takes place at the specified time on the  
current day (if the specified time is later than the current time) or on the next day (if the specified  
time is earlier than the current time). Specifying 00:00 schedules the reload for midnight.  
Note  
Use the at keyword only if the switch system clock has been set (through Network Time  
Protocol (NTP), the hardware calendar, or manually). The time is relative to the configured  
time zone on the switch. To schedule reloads across several switches to occur  
simultaneously, the time on each switch must be synchronized with NTP.  
The reload command halts the system. If the system is not set to manually boot, it reboots itself. Use the  
reload command after you save the switch configuration information to the startup configuration (copy  
running-config startup-config).  
If your switch is configured for manual booting, do not reload it from a virtual terminal. This restriction  
prevents the switch from entering the boot loader mode and thereby taking it from the remote user’s  
control.  
If you modify your configuration file, the switch prompts you to save the configuration before reloading.  
During the save operation, the system requests whether you want to proceed with the save if the  
CONFIG_FILE environment variable points to a startup configuration file that no longer exists. If you  
proceed in this situation, the system enters setup mode upon reload.  
This example shows how to reload the software on the switch on the current day at 7:30 p.m:  
Switch# reload at 19:30  
Reload scheduled for 19:30:00 UTC Wed Jun 5 1996 (in 2 hours and 25 minutes)  
Proceed with reload? [confirm]  
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Scheduling a Reload of the Software Image  
This example shows how to reload the software on the switch at a future time:  
Switch# reload at 02:00 jun 20  
Reload scheduled for 02:00:00 UTC Thu Jun 20 1996 (in 344 hours and 53 minutes)  
Proceed with reload? [confirm]  
To cancel a previously scheduled reload, use the reload cancel privileged EXEC command.  
Displaying Scheduled Reload Information  
To display information about a previously scheduled reload or to determine if a reload has been  
scheduled on the switch, use the show reload privileged EXEC command.  
It displays reload information including the time the reload is scheduled to occur and the reason for the  
reload (if it was specified when the reload was scheduled).  
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C H A P T E R  
4
Administering the Switch  
This chapter describes how to perform one-time operations to administer your Cisco Systems Intelligent  
Gigabit Ethernet Switch Module. This chapter consists of these sections:  
•
•
•
•
•
Managing the System Time and Date, page 4-1  
Configuring a System Name and Prompt, page 4-13  
Creating a Banner, page 4-16  
Managing the MAC Address Table, page 4-18  
Managing the ARP Table, page 4-24  
Managing the System Time and Date  
You can manage the system time and date on your switch using automatic configuration, such as the  
Network Time Protocol (NTP), or manual configuration methods.  
Note  
For complete syntax and usage information for the commands used in this section, see the Cisco IOS  
Configuration Fundamentals Command Reference for Cisco IOS, Release 12.1.  
This section contains this configuration information:  
•
•
•
•
Understanding the System Clock, page 4-1  
Understanding Network Time Protocol, page 4-2  
Configuring NTP, page 4-3  
Configuring Time and Date Manually, page 4-10  
Understanding the System Clock  
The heart of the time service is the system clock. This clock runs from the moment the system starts up  
and keeps track of the date and time.  
The system clock can then be set from these sources:  
•
•
Network Time Protocol  
Manual configuration  
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Managing the System Time and Date  
The system clock can provide time to these services:  
•
•
User show commands  
Logging and debugging messages  
The system clock keeps track of time internally based on Universal Time Coordinated (UTC), also  
known as Greenwich Mean Time (GMT). You can configure information about the local time zone and  
summer time (daylight saving time) so that the time appears correctly for the local time zone.  
The system clock keeps track of whether the time is authoritative or not (that is, whether it has been set  
by a time source considered to be authoritative). If it is not authoritative, the time is available only for  
display purposes and is not redistributed. For configuration information, see the “Configuring Time and  
Date Manually” section on page 4-10.  
Understanding Network Time Protocol  
The NTP is designed to time-synchronize a network of devices. NTP runs over User Datagram Protocol  
(UDP), which runs over IP. NTP is documented in RFC 1305.  
An NTP network usually gets its time from an authoritative time source, such as a radio clock or an  
atomic clock attached to a time server. NTP then distributes this time across the network. NTP is  
extremely efficient; no more than one packet per minute is necessary to synchronize two devices to  
within a millisecond of one another.  
NTP uses the concept of a stratum to describe how many NTP hops away a device is from an  
authoritative time source. A stratum 1 time server has a radio or atomic clock directly attached, a  
stratum 2 time server receives its time through NTP from a stratum 1 time server, and so on. A device  
running NTP automatically chooses as its time source the device with the lowest stratum number with  
which it communicates through NTP. This strategy effectively builds a self-organizing tree of NTP  
speakers.  
NTP avoids synchronizing to a device whose time might not be accurate by never synchronizing to a  
device that is not synchronized. NTP also compares the time reported by several devices and does not  
synchronize to a device whose time is significantly different than the others, even if its stratum is lower.  
The communications between devices running NTP (known as associations) are usually statically  
configured; each device is given the IP address of all devices with which it should form associations.  
Accurate timekeeping is possible by exchanging NTP messages between each pair of devices with an  
association. However, in a LAN environment, NTP can be configured to use IP broadcast messages  
instead. This alternative reduces configuration complexity because each device can simply be  
configured to send or receive broadcast messages. However, in that case, information flow is one-way  
only.  
The time kept on a device is a critical resource; you should use the security features of NTP to avoid the  
accidental or malicious setting of an incorrect time. Two mechanisms are available: an access list-based  
restriction scheme and an encrypted authentication mechanism.  
Cisco’s implementation of NTP does not support stratum 1 service; it is not possible to connect to a radio  
or atomic clock. We recommend that the time service for your network be derived from the public NTP  
servers available on the IP Internet.  
Figure 4-1 show a typical network example using NTP.  
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Chapter 4 Administering the Switch  
Managing the System Time and Date  
Figure 4-1  
Typical NTP Network Configuration  
Catalyst 6500  
series switch  
(NTP master)  
Local  
workgroup  
servers  
Catalyst 2950, 2955,  
or 3550 switch  
Catalyst 2950, 2955,  
or 3550 switch  
Catalyst 2950, 2955,  
or 3550 switch  
These switches are configured in  
NTP server mode (server association)  
with the Catalyst 6500 series switch.  
BladeCenter  
If the network is isolated from the Internet, Cisco’s implementation of NTP allows a device to act as  
though it is synchronized through NTP, when in fact it has determined the time by using other means.  
Other devices then synchronize to that device through NTP.  
When multiple sources of time are available, NTP is always considered to be more authoritative. NTP  
time overrides the time set by any other method.  
Several manufacturers include NTP software for their host systems, and a publicly available version for  
systems running UNIX and its various derivatives is also available. This software allows host systems  
to be time-synchronized as well.  
Configuring NTP  
The switch does not have a hardware-supported clock, and it cannot function as an NTP master clock to  
which peers synchronize themselves when an external NTP source is not available. The switch also has  
no hardware support for a calendar. As a result, the ntp update-calendar and the ntp master global  
configuration commands are not available.  
This section contains this configuration information:  
•
•
•
•
•
•
•
Default NTP Configuration, page 4-4  
Configuring NTP Authentication, page 4-4  
Configuring NTP Associations, page 4-5  
Configuring NTP Broadcast Service, page 4-6  
Configuring NTP Access Restrictions, page 4-7  
Configuring the Source IP Address for NTP Packets, page 4-9  
Displaying the NTP Configuration, page 4-10  
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Managing the System Time and Date  
Default NTP Configuration  
Table 4-1 shows the default NTP configuration.  
Table 4-1  
Default NTP Configuration  
Feature  
Default Setting  
NTP authentication  
Disabled. No authentication key is specified.  
None configured.  
NTP peer or server associations  
NTP broadcast service  
Disabled; no interface sends or receives NTP broadcast packets.  
No access control is specified.  
NTP access restrictions  
NTP packet source IP address  
The source address is determined by the outgoing interface.  
NTP is enabled on all interfaces by default. All interfaces receive NTP packets.  
Configuring NTP Authentication  
This procedure must be coordinated with the administrator of the NTP server; the information you configure  
in this procedure must be matched by the servers used by the switch to synchronize its time to the NTP server.  
Beginning in privileged EXEC mode, follow these steps to authenticate the associations (communications  
between devices running NTP that provide for accurate timekeeping) with other devices for security  
purposes:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
ntp authenticate  
Enter global configuration mode.  
Enable the NTP authentication feature, which is disabled by  
default.  
Step 3  
Step 4  
4-4  
ntp authentication-key number md5 value Define the authentication keys. By default, none are defined.  
•
•
•
For number, specify a key number. The range is 1 to  
4294967295.  
md5 specifies that message authentication support is provided  
by using the message digest algorithm 5 (MD5).  
For value, enter an arbitrary string of up to eight characters for  
the key.  
The switch does not synchronize to a device unless both have one  
of these authentication keys, and the key number is specified by the  
ntp trusted-key key-number command.  
ntp trusted-key key-number  
Specify one or more key numbers (defined in Step 3) that a peer  
NTP device must provide in its NTP packets for this switch to  
synchronize to it.  
By default, no trusted keys are defined.  
For key-number, specify the key defined in Step 3.  
This command provides protection against accidentally  
synchronizing the switch to a device that is not trusted.  
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Managing the System Time and Date  
Command  
Purpose  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
Step 6  
Step 7  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable NTP authentication, use the no ntp authenticate global configuration command. To remove  
an authentication key, use the no ntp authentication-key number global configuration command. To  
disable authentication of the identity of a device, use the no ntp trusted-key key-number global  
configuration command.  
This example shows how to configure the switch to synchronize only to devices providing authentication  
key 42 in the device’s NTP packets:  
Switch(config)# ntp authenticate  
Switch(config)# ntp authentication-key 42 md5 aNiceKey  
Switch(config)# ntp trusted-key 42  
Configuring NTP Associations  
An NTP association can be a peer association (this switch can either synchronize to the other device or  
allow the other device to synchronize to it), or it can be a server association (meaning that only this  
switch synchronizes to the other device, and not the other way around).  
Beginning in privileged EXEC mode, follow these steps to form an NTP association with another device:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ntp peer ip-address [version number]  
Configure the switch system clock to synchronize a peer or to be  
[key keyid] [source interface] [prefer] synchronized by a peer (peer association).  
or or  
ntp server ip-address [version number] Configure the switch system clock to be synchronized by a time server  
[key keyid] [source interface] [prefer] (server association).  
No peer or server associations are defined by default.  
•
For ip-address in a peer association, specify either the IP address of  
the peer providing, or being provided, the clock synchronization. For  
a server association, specify the IP address of the time server  
providing the clock synchronization.  
•
•
•
(Optional) For number, specify the NTP version number. The range is  
1 to 3. By default, version 3 is selected.  
(Optional) For keyid, enter the authentication key defined with the  
ntp authentication-key global configuration command.  
(Optional) For interface, specify the interface from which to pick the  
IP source address. By default, the source IP address is taken from the  
outgoing interface.  
•
(Optional) Enter the prefer keyword to make this peer or server the  
preferred one that provides synchronization. This keyword reduces  
switching back and forth between peers and servers.  
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Command  
Purpose  
Step 3  
end  
Return to privileged EXEC mode.  
Verify your entries.  
Step 4  
Step 5  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
You need to configure only one end of an association; the other device can automatically establish the  
association. If you are using the default NTP version (version 3) and NTP synchronization does not  
occur, try using NTP version 2. Many NTP servers on the Internet run version 2.  
To remove a peer or server association, use the no ntp peer ip-address or the no ntp server ip-address  
global configuration command.  
This example shows how to configure the switch to synchronize its system clock with the clock of the  
peer at IP address 172.16.22.44 using NTP version 2:  
Switch(config)# ntp server 172.16.22.44 version 2  
Configuring NTP Broadcast Service  
The communications between devices running NTP (known as associations) are usually statically  
configured; each device is given the IP addresses of all devices with which it should form associations.  
Accurate timekeeping is possible by exchanging NTP messages between each pair of devices with an  
association. However, in a LAN environment, NTP can be configured to use IP broadcast messages  
instead. This alternative reduces configuration complexity because each device can simply be  
configured to send or receive broadcast messages. However, the information flow is one-way only.  
The switch can send or receive NTP broadcast packets on an interface-by-interface basis if there is an NTP  
broadcast server, such as a router, broadcasting time information on the network. The switch can send NTP  
broadcast packets to a peer so that the peer can synchronize to it. The switch can also receive NTP broadcast  
packets to synchronize its own clock. This section has procedures for both sending and receiving NTP  
broadcast packets.  
Beginning in privileged EXEC mode, follow these steps to configure the switch to send NTP broadcast  
packets to peers so that they can synchronize their clock to the switch:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to send NTP broadcast packets, and enter  
interface configuration mode.  
Step 3  
ntp broadcast [version number] [key keyid] Enable the interface to send NTP broadcast packets to a peer.  
[destination-address]  
By default, this feature is disabled on all interfaces.  
•
•
•
(Optional) For number, specify the NTP version number. The  
range is 1 to 3. If you do not specify a version, version 3 is used.  
(Optional) For keyid, specify the authentication key to use when  
sending packets to the peer.  
(Optional) For destination-address, specify the IP address of the  
peer that is synchronizing its clock to this switch.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
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Command  
Purpose  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Step 7  
Configure the connected peers to receive NTP broadcast packets as  
described in the next procedure.  
To disable the interface from sending NTP broadcast packets, use the no ntp broadcast interface  
configuration command.  
This example shows how to configure a port to send NTP version 2 packets:  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# ntp broadcast version 2  
Beginning in privileged EXEC mode, follow these steps to configure the switch to receive NTP  
broadcast packets from connected peers:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to receive NTP broadcast packets, and enter interface  
configuration mode.  
Step 3  
ntp broadcast client  
Enable the interface to receive NTP broadcast packets.  
By default, no interfaces receive NTP broadcast packets.  
Return to global configuration mode.  
Step 4  
Step 5  
exit  
ntp broadcastdelay microseconds  
(Optional) Change the estimated round-trip delay between the switch and  
the NTP broadcast server.  
The default is 3000 microseconds; the range is 1 to 999999.  
Return to privileged EXEC mode.  
Step 6  
Step 7  
Step 8  
end  
show running-config  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable an interface from receiving NTP broadcast packets, use the no ntp broadcast client interface  
configuration command. To change the estimated round-trip delay to the default, use the no ntp  
broadcastdelay global configuration command.  
This example shows how to configure a port to receive NTP broadcast packets:  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# ntp broadcast client  
Configuring NTP Access Restrictions  
You can control NTP access on two levels as described in these sections:  
•
•
Creating an Access Group and Assigning a Basic IP Access List, page 4-8  
Disabling NTP Services on a Specific Interface, page 4-9  
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Chapter 4 Administering the Switch  
Managing the System Time and Date  
Creating an Access Group and Assigning a Basic IP Access List  
Beginning in privileged EXEC mode, follow these steps to control access to NTP services by using  
access lists:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ntp access-group {query-only |  
serve-only | serve | peer}  
access-list-number  
Create an access group, and apply a basic IP access list.  
The keywords have these meanings:  
•
•
•
query-only—Allows only NTP control queries.  
serve-only—Allows only time requests.  
serve—Allows time requests and NTP control queries, but does not  
allow the switch to synchronize to the remote device.  
•
peer—Allows time requests and NTP control queries and allows the  
switch to synchronize to the remote device.  
For access-list-number, enter a standard IP access list number from 1  
to 99.  
Step 3  
access-list access-list-number permit  
source [source-wildcard]  
Create the access list.  
•
•
For access-list-number, enter the number specified in Step 2.  
Enter the permit keyword to permit access if the conditions are  
matched.  
•
For source, enter the IP address of the device that is permitted access  
to the switch.  
•
(Optional) For source-wildcard, enter the wildcard bits to be applied  
to the source.  
Note  
When creating an access list, remember that, by default, the end  
of the access list contains an implicit deny statement for  
everything if it did not find a match before reaching the end.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
The access group keywords are scanned in this order, from least restrictive to most restrictive:  
1. peer—Allows time requests and NTP control queries and allows the switch to synchronize itself to  
a device whose address passes the access list criteria.  
2. serve—Allows time requests and NTP control queries, but does not allow the switch to synchronize  
itself to a device whose address passes the access list criteria.  
3. serve-only—Allows only time requests from a device whose address passes the access list criteria.  
4. query-only—Allows only NTP control queries from a device whose address passes the access list  
criteria.  
If the source IP address matches the access lists for more than one access type, the first type is granted.  
If no access groups are specified, all access types are granted to all devices. If any access groups are  
specified, only the specified access types are granted.  
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Chapter 4 Administering the Switch  
Managing the System Time and Date  
To remove access control to the switch NTP services, use the no ntp access-group {query-only |  
serve-only | serve | peer} global configuration command.  
This example shows how to configure the switch to allow itself to synchronize to a peer from access  
list 99. However, the switch restricts access to allow only time requests from access list 42:  
Switch# configure terminal  
Switch(config)# ntp access-group peer 99  
Switch(config)# ntp access-group serve-only 42  
Switch(config)# access-list 99 permit 172.20.130.5  
Switch(config)# access list 42 permit 172.20.130.6  
Disabling NTP Services on a Specific Interface  
NTP services are enabled on all interfaces by default.  
Beginning in privileged EXEC mode, follow these steps to disable NTP packets from being received on  
an interface:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
interface interface-id  
ntp disable  
Enter global configuration mode.  
Enter interface configuration mode, and specify the interface to disable.  
Disable NTP packets from being received on the interface.  
By default, all interfaces receive NTP packets.  
Return to privileged EXEC mode.  
Step 4  
Step 5  
Step 6  
end  
show running-config  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To re-enable receipt of NTP packets on an interface, use the no ntp disable interface configuration  
command.  
Configuring the Source IP Address for NTP Packets  
When the switch sends an NTP packet, the source IP address is normally set to the address of the interface  
through which the NTP packet is sent. Use the ntp source global configuration command when you want to  
use a particular source IP address for all NTP packets. The address is taken from the specified interface. This  
command is useful if the address on an interface cannot be used as the destination for reply packets.  
Beginning in privileged EXEC mode, follow these steps to configure a specific interface from which the  
IP source address is to be taken:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ntp source type number  
Specify the interface type and number from which the IP source address  
is taken.  
By default, the source address is determined by the outgoing interface.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
Step 5  
end  
show running-config  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 4 Administering the Switch  
Managing the System Time and Date  
The specified interface is used for the source address for all packets sent to all destinations. If a source address  
is to be used for a specific association, use the source keyword in the ntp peer or ntp server global  
configuration command as described in the “Configuring NTP Associations” section on page 4-5.  
Displaying the NTP Configuration  
You can use two privileged EXEC commands to display NTP information:  
•
•
show ntp associations [detail]  
show ntp status  
For detailed information about the fields in these displays, see the Cisco IOS Configuration  
Fundamentals Command Reference for Cisco IOS, Release 12.1.  
Configuring Time and Date Manually  
If no other source of time is available, you can manually configure the time and date after the system is  
restarted. The time remains accurate until the next system restart. We recommend that you use manual  
configuration only as a last resort. If you have an outside source to which the switch can synchronize,  
you do not need to manually set the system clock.  
This section contains this configuration information:  
•
•
•
•
Setting the System Clock, page 4-10  
Displaying the Time and Date Configuration, page 4-11  
Configuring the Time Zone, page 4-11  
Configuring Summer Time (Daylight Saving Time), page 4-12  
Setting the System Clock  
If you have an outside source on the network that provides time services, such as an NTP server, you do  
not need to manually set the system clock.  
Beginning in privileged EXEC mode, follow these steps to set the system clock:  
Command  
Purpose  
Step 1  
clock set hh:mm:ss day month year  
or  
Manually set the system clock using one of these formats.  
•
For hh:mm:ss, specify the time in hours (24-hour format), minutes,  
and seconds. The time specified is relative to the configured time  
zone.  
clock set hh:mm:ss month day year  
•
•
•
For day, specify the day by date in the month.  
For month, specify the month by name.  
For year, specify the year (no abbreviation).  
Step 2  
Step 3  
show running-config  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
This example shows how to manually set the system clock to 1:32 p.m. on July 23, 2001:  
Switch# clock set 13:32:00 23 July 2001  
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Chapter 4 Administering the Switch  
Managing the System Time and Date  
Displaying the Time and Date Configuration  
To display the time and date configuration, use the show clock [detail] privileged EXEC command.  
The system clock keeps an authoritative flag that shows whether the time is authoritative (believed to  
be accurate). If the system clock has been set by a timing source such as NTP, the flag is set. If the time  
is not authoritative, it is used only for display purposes. Until the clock is authoritative and the  
authoritative flag is set, the flag prevents peers from synchronizing to the clock when the peers’ time is  
invalid.  
The symbol that precedes the show clock display has this meaning:  
•
•
•
*—Time is not authoritative.  
(blank)—Time is authoritative.  
.—Time is authoritative, but NTP is not synchronized.  
Configuring the Time Zone  
Beginning in privileged EXEC mode, follow these steps to manually configure the time zone:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Set the time zone.  
clock timezone zone hours-offset  
[minutes-offset]  
The switch keeps internal time in universal time coordinated (UTC), so  
this command is used only for display purposes and when the time is  
manually set.  
•
For zone, enter the name of the time zone to be displayed when  
standard time is in effect. The default is UTC.  
•
•
For hours-offset, enter the hours offset from UTC.  
(Optional) For minutes-offset, enter the minutes offset from UTC.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
The minutes-offset variable in the clock timezone global configuration command is available for those  
cases where a local time zone is a percentage of an hour different from UTC. For example, the time zone  
for some sections of Atlantic Canada (AST) is UTC-3.5, where the 3 means 3 hours and .5 means 50  
percent. In this case, the necessary command is clock timezone AST -3 30.  
To set the time to UTC, use the no clock timezone global configuration command.  
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Chapter 4 Administering the Switch  
Managing the System Time and Date  
Configuring Summer Time (Daylight Saving Time)  
Beginning in privileged EXEC mode, follow these steps to configure summer time (daylight saving  
time) in areas where it starts and ends on a particular day of the week each year:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
clock summer-time zone recurring  
[week day month hh:mm week day month  
hh:mm [offset]]  
Configure summer time to start and end on the specified days every year.  
Summer time is disabled by default. If you specify clock summer-time  
zone recurring without parameters, the summer time rules default to the  
United States rules.  
•
For zone, specify the name of the time zone (for example, PDT) to be  
displayed when summer time is in effect.  
•
•
•
•
(Optional) For week, specify the week of the month (1 to 5 or last).  
(Optional) For day, specify the day of the week (Sunday, Monday...).  
(Optional) For month, specify the month (January, February...).  
(Optional) For hh:mm, specify the time (24-hour format) in hours and  
minutes.  
•
(Optional) For offset, specify the number of minutes to add during  
summer time. The default is 60.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
The first part of the clock summer-time global configuration command specifies when summer time  
begins, and the second part specifies when it ends. All times are relative to the local time zone. The start  
time is relative to standard time. The end time is relative to summer time. If the starting month is after  
the ending month, the system assumes that you are in the southern hemisphere.  
This example shows how to specify that summer time starts on the first Sunday in April at 02:00 and  
ends on the last Sunday in October at 02:00:  
Switch(config)# clock summer-time PDT recurring 1 Sunday April 2:00 last Sunday October  
2:00  
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Chapter 4 Administering the Switch  
Configuring a System Name and Prompt  
Beginning in privileged EXEC mode, follow these steps if summer time in your area does not follow a  
recurring pattern (configure the exact date and time of the next summer time events):  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
clock summer-time zone date [month  
Configure summer time to start on the first date and end on the second  
date year hh:mm month date year hh:mm date.  
[offset]]  
Summer time is disabled by default.  
or  
•
For zone, specify the name of the time zone (for example, PDT) to be  
clock summer-time zone date [date  
month year hh:mm date month year  
hh:mm [offset]]  
displayed when summer time is in effect.  
•
•
•
•
(Optional) For week, specify the week of the month (1 to 5 or last).  
(Optional) For day, specify the day of the week (Sunday, Monday...).  
(Optional) For month, specify the month (January, February...).  
(Optional) For hh:mm, specify the time (24-hour format) in hours and  
minutes.  
•
(Optional) For offset, specify the number of minutes to add during  
summer time. The default is 60.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
The first part of the clock summer-time global configuration command specifies when summer time  
begins, and the second part specifies when it ends. All times are relative to the local time zone. The start  
time is relative to standard time. The end time is relative to summer time. If the starting month is after  
the ending month, the system assumes that you are in the southern hemisphere.  
To disable summer time, use the no clock summer-time global configuration command.  
This example shows how to set summer time to start on October 12, 2000, at 02:00, and end on April  
26, 2001, at 02:00:  
Switch(config)# clock summer-time pdt date 12 October 2000 2:00 26 April 2001 2:00  
Configuring a System Name and Prompt  
You configure the system name on the switch to identify it. By default, the system name and prompt are  
Switch.  
If you have not configured a system prompt, the first 20 characters of the system name are used as the  
system prompt. A greater-than symbol [>] is appended. The prompt is updated whenever the system  
name changes.  
Note  
For complete syntax and usage information for the commands used in this section, see the Cisco IOS  
Configuration Fundamentals Command Reference for Cisco IOS Release 12.1 and the Cisco IOS IP and  
IP Routing Command Reference for Cisco IOS Release 12.1.  
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Chapter 4 Administering the Switch  
Configuring a System Name and Prompt  
This section contains this configuration information:  
•
•
•
Default System Name and Prompt Configuration, page 4-14  
Configuring a System Name, page 4-14  
Understanding DNS, page 4-14  
Default System Name and Prompt Configuration  
The default switch system name and prompt is Switch.  
Configuring a System Name  
Beginning in privileged EXEC mode, follow these steps to manually configure a system name:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Manually configure a system name.  
The default setting is switch.  
hostname name  
The name must follow the rules for ARPANET host names. They must start  
with a letter, end with a letter or digit, and have as interior characters only  
letters, digits, and hyphens. Names can be up to 63 characters.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
When you set the system name, it is also used as the system prompt.  
To return to the default hostname, use the no hostname global configuration command.  
Understanding DNS  
The DNS protocol controls the Domain Name System (DNS), a distributed database with which you can  
map host names to IP addresses. When you configure DNS on your switch, you can substitute the host  
name for the IP address with all IP commands, such as ping, telnet, connect, and related Telnet support  
operations.  
IP defines a hierarchical naming scheme that allows a device to be identified by its location or domain.  
Domain names are pieced together with periods (.) as the delimiting characters. For example, IBM is a  
commercial organization that IP identifies by a com domain name, so its domain name is ibm.com. A  
specific device in this domain, for example, the File Transfer Protocol (FTP) system is identified as  
ftp.ibm.com.  
To keep track of domain names, IP has defined the concept of a domain name server, which holds a cache  
(or database) of names mapped to IP addresses. To map domain names to IP addresses, you must first  
identify the host names, specify the name server that is present on your network, and enable the DNS.  
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Chapter 4 Administering the Switch  
Configuring a System Name and Prompt  
This section contains this configuration information:  
•
•
•
Default DNS Configuration, page 4-15  
Setting Up DNS, page 4-15  
Displaying the DNS Configuration, page 4-16  
Default DNS Configuration  
Table 4-2 shows the default DNS configuration.  
Table 4-2  
Default DNS Configuration  
Feature  
Default Setting  
Enabled.  
DNS enable state  
DNS default domain name  
DNS servers  
None configured.  
No name server addresses are configured.  
Setting Up DNS  
Beginning in privileged EXEC mode, follow these steps to set up your switch to use the DNS:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
ip domain-name name  
Enter global configuration mode.  
Define a default domain name that the software uses to complete unqualified  
host names (names without a dotted-decimal domain name).  
Do not include the initial period that separates an unqualified name from the  
domain name.  
At boot time, no domain name is configured.  
Step 3  
Step 4  
ip name-server server-address1 Specify the address of one or more name servers to use for name and address  
[server-address2 ...  
server-address6]  
resolution.  
You can specify up to six name servers. Separate each server address with a  
space. The first server specified is the primary server. The switch sends DNS  
queries to the primary server first. If that query fails, the backup servers are  
queried.  
ip domain-lookup  
(Optional) Enable DNS-based host name-to-address translation on your switch.  
This feature is enabled by default.  
If your network devices require connectivity with devices in networks for which  
you do not control name assignment, you can dynamically assign device names  
that uniquely identify your devices by using the global Internet naming scheme  
(DNS).  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config  
startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 4 Administering the Switch  
Creating a Banner  
If you use the switch IP address as its hostname, the IP address is used and no DNS query occurs. If you  
configure a hostname that contains no periods (.), a period followed by the default domain name is  
appended to the hostname before the DNS query is made to map the name to an IP address. The default  
domain name is the value set by the ip domain-name global configuration command. If there is a  
period (.) in the hostname, the software looks up the IP address without appending any default domain  
name to the hostname.  
To remove a domain name, use the no ip domain-name name global configuration command. To  
remove a name server address, use the no ip name-server server-address global configuration  
command. To disable DNS on the switch, use the no ip domain-lookup global configuration command.  
Displaying the DNS Configuration  
To display the DNS configuration information, use the show running-config privileged EXEC  
command.  
Creating a Banner  
You can configure a message-of-the-day (MOTD) and a login banner. The MOTD banner displays on  
all connected terminals at login and is useful for sending messages that affect all network users (such as  
impending system shutdowns).  
The login banner also displays on all connected terminals. It appears after the MOTD banner and before  
the login prompts.  
Note  
For complete syntax and usage information for the commands used in this section, see the Cisco IOS  
Configuration Fundamentals Command Reference for Cisco IOS, Release 12.1.  
This section contains this configuration information:  
•
•
•
Default Banner Configuration, page 4-16  
Configuring a Message-of-the-Day Login Banner, page 4-16  
Configuring a Login Banner, page 4-18  
Default Banner Configuration  
The MOTD and login banners are not configured.  
Configuring a Message-of-the-Day Login Banner  
You can create a single or multiline message banner that appears on the screen when someone logs in to  
the switch.  
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Chapter 4 Administering the Switch  
Creating a Banner  
Beginning in privileged EXEC mode, follow these steps to configure a MOTD login banner:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
banner motd c message c  
Enter global configuration mode.  
Specify the message of the day.  
For c, enter the delimiting character of your choice, for example, a  
pound sign (#), and press the Return key. The delimiting character  
signifies the beginning and end of the banner text. Characters after the  
ending delimiter are discarded.  
For message, enter a banner message up to 255 characters. You cannot  
use the delimiting character in the message.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To delete the MOTD banner, use the no banner motd global configuration command.  
This example shows how to configure a MOTD banner for the switch by using the pound sign (#) symbol  
as the beginning and ending delimiter:  
Switch(config)# banner motd #  
This is a secure site. Only authorized users are allowed.  
For access, contact technical support.  
#
Switch(config)#  
This example shows the banner displayed from the previous configuration:  
Unix> telnet 172.2.5.4  
Trying 172.2.5.4...  
Connected to 172.2.5.4.  
Escape character is '^]'.  
This is a secure site. Only authorized users are allowed.  
For access, contact technical support.  
User Access Verification  
Password:  
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Chapter 4 Administering the Switch  
Managing the MAC Address Table  
Configuring a Login Banner  
You can configure a login banner to be displayed on all connected terminals. This banner appears after  
the MOTD banner and before the login prompt.  
Beginning in privileged EXEC mode, follow these steps to configure a login banner:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Specify the login message.  
banner login c message c  
For c, enter the delimiting character of your choice, for example, a pound  
sign (#), and press the Return key. The delimiting character signifies the  
beginning and end of the banner text. Characters after the ending delimiter  
are discarded.  
For message, enter a login message up to 255 characters. You cannot use the  
delimiting character in the message.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To delete the login banner, use the no banner login global configuration command.  
This example shows how to configure a login banner for the switch by using the dollar sign ($) symbol  
as the beginning and ending delimiter:  
Switch(config)# banner login $  
Access for authorized users only. Please enter your username and password.  
$
Switch(config)#  
Managing the MAC Address Table  
The MAC address table contains address information that the switch uses to forward traffic between  
ports. All MAC addresses in the address table are associated with one or more ports. The address table  
includes these types of addresses:  
•
•
Dynamic address: a source MAC address that the switch learns and then ages when it is not in use.  
Static address: a manually entered unicast or multicast address that does not age and that is not lost  
when the switch resets.  
The address table lists the destination MAC address, the associated VLAN ID, and port number  
associated with the address.  
Note  
For complete syntax and usage information for the commands used in this section, see the command  
reference for this release.  
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Chapter 4 Administering the Switch  
Managing the MAC Address Table  
This section contains this configuration information:  
•
•
•
•
•
•
•
•
Building the Address Table, page 4-19  
MAC Addresses and VLANs, page 4-19  
Default MAC Address Table Configuration, page 4-20  
Changing the Address Aging Time, page 4-20  
Removing Dynamic Address Entries, page 4-20  
Configuring MAC Address Notification Traps, page 4-21  
Adding and Removing Static Address Entries, page 4-23  
Displaying Address Table Entries, page 4-24  
Building the Address Table  
With multiple MAC addresses supported on all ports, you can connect any port on the switch to  
individual workstations, repeaters, switches, routers, or other network devices. The switch provides  
dynamic addressing by learning the source address of packets it receives on each port and adding the  
address and its associated port number to the address table. As stations are added or removed from the  
network, the switch updates the address table, adding new dynamic addresses and aging out those that  
are not in use.  
The aging interval is configured on a per-switch basis. However, the switch maintains an address table  
for each VLAN, and STP can accelerate the aging interval on a per-VLAN basis.  
The switch sends packets between any combination of ports, based on the destination address of the  
received packet. Using the MAC address table, the switch forwards the packet only to the port or ports  
associated with the destination address. If the destination address is on the port that sent the packet, the  
packet is filtered and not forwarded. The switch always uses the store-and-forward method: complete  
packets are stored and checked for errors before transmission.  
MAC Addresses and VLANs  
All addresses are associated with a VLAN. An address can exist in more than one VLAN and have  
different destinations in each. Multicast addresses, for example, could be forwarded to port 1 in VLAN 1  
and ports 9, 10, and 11 in VLAN 5.  
Each VLAN maintains its own logical address table. A known address in one VLAN is unknown in  
another until it is learned or statically associated with a port in the other VLAN. Addresses that are  
statically entered in one VLAN must be configured as static addresses in all other VLANs or remain  
unlearned in the other VLANs.  
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Managing the MAC Address Table  
Default MAC Address Table Configuration  
Table 4-3 shows the default MAC address table configuration.  
Table 4-3  
Default MAC Address Table Configuration  
Feature  
Default Setting  
Aging time  
300 seconds  
Dynamic addresses  
Static addresses  
Automatically learned  
None configured  
Changing the Address Aging Time  
Dynamic addresses are source MAC addresses that the switch learns and then ages when they are not in  
use. The aging time parameter defines how long the switch retains unseen addresses. This parameter  
applies to all VLANs.  
Setting too short an aging time can cause addresses to be prematurely removed from the table. Then  
when the switch receives a packet for an unknown destination, it floods the packet to all ports in the same  
VLAN as the receiving port. This unnecessary flooding can impact performance. Setting too long an  
aging time can cause the address table to be filled with unused addresses, which prevents new addresses  
from being learned.  
Beginning in privileged EXEC mode, follow these steps to configure the dynamic address table aging  
time:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
mac address-table aging-time [0 |  
10-1000000]  
Set the length of time that a dynamic entry remains in the MAC  
address table after the entry is used or updated.  
The range is 10 to 1000000 seconds. The default is 300. You can also  
enter 0, which disables aging. Static address entries are never aged  
or removed from the table.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show mac address-table aging-time  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return to the default value, use the no mac address-table aging-time global configuration command.  
Removing Dynamic Address Entries  
To remove all dynamic entries, use the clear mac address-table dynamic command in privileged EXEC  
mode. You can also remove a specific MAC address (clear mac address-table dynamic address  
mac-address), remove all addresses on the specified physical port or port channel (clear mac  
address-table dynamic interface interface-id), or remove all addresses on a specified VLAN (clear  
mac address-table dynamic vlan vlan-id).  
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Chapter 4 Administering the Switch  
Managing the MAC Address Table  
To verify that dynamic entries have been removed, use the show mac address-table dynamic privileged  
EXEC command.  
Configuring MAC Address Notification Traps  
MAC address notification enables you to track users on a network by storing the MAC address activity  
on the switch. Whenever the switch learns or removes a MAC address, an SNMP notification can be  
generated and sent to the NMS. If you have many users coming and going from the network, you can set  
a trap interval time to bundle the notification traps and reduce network traffic. The MAC notification  
history table stores the MAC address activity for each hardware port for which the trap is enabled. MAC  
address notifications are generated for dynamic and secure MAC addresses; events are not generated for  
self addresses, multicast addresses, or other static addresses.  
Beginning in privileged EXEC mode, follow these steps to configure the switch to send MAC address  
notification traps to an NMS host:  
Command  
configure terminal  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
snmp-server host host-addr {traps | informs} {version {1 Specify the recipient of the trap message.  
| 2c | 3}} community-string notification-type  
•
For host-addr, specify the name or address of the  
NMS.  
•
Specify traps (the default) to send SNMP traps  
to the host. Specify informs to send SNMP  
informs to the host.  
•
•
Specify the SNMP version to support. Version 1,  
the default, is not available with informs.  
For community-string, specify the string to send  
with the notification operation. Though you can  
set this string by using the snmp-server host  
command, we recommend that you define this  
string by using the snmp-server community  
command before using the snmp-server host  
command.  
•
For notification-type, use the mac-notification  
keyword.  
Step 3  
Step 4  
snmp-server enable traps mac-notification  
mac address-table notification  
Enable the switch to send MAC address traps to the  
NMS.  
Enable the MAC address notification feature.  
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Chapter 4 Administering the Switch  
Managing the MAC Address Table  
Command  
Purpose  
Enter the trap interval time and the history table size.  
Step 5  
mac address-table notification [interval value] |  
[history-size value]  
•
(Optional) For interval value, specify the  
notification trap interval in seconds between  
each set of traps that are generated to the NMS.  
The range is 0 to 2147483647 seconds; the  
default is 1 second.  
•
(Optional) For history-size value, specify the  
maximum number of entries in the MAC  
notification history table. The range is 0 to 500;  
the default is 1.  
Step 6  
Step 7  
interface interface-id  
Enter interface configuration mode, and specify the  
interface on which to enable the SNMP MAC  
address notification trap.  
snmp trap mac-notification {added | removed}  
Enable the MAC address notification trap.  
•
Enable the MAC notification trap whenever a  
MAC address is added on this interface.  
•
Enable the MAC notification trap whenever a  
MAC address is removed from this interface.  
Step 8  
Step 9  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show mac address-table notification interface  
show running-config  
Step 10  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable the switch from sending MAC address notification traps, use the no snmp-server enable  
traps mac-notification global configuration command. To disable the MAC address notification traps  
on a specific interface, use the no snmp trap mac-notification {added | removed} interface  
configuration command. To disable the MAC address notification feature, use the no mac address-table  
notification global configuration command.  
This example shows how to specify 172.20.10.10 as the NMS, enable the switch to send MAC address  
notification traps to the NMS, enable the MAC address notification feature, set the interval time to  
60 seconds, set the history-size to 100 entries, and enable traps whenever a MAC address is added on  
the specified port.  
Switch(config)# snmp-server host 172.20.10.10 traps private  
Switch(config)# snmp-server enable traps mac-notification  
Switch(config)# mac address-table notification  
Switch(config)# mac address-table notification interval 60  
Switch(config)# mac address-table notification history-size 100  
Switch(config)# interface fastethernet0/4  
Switch(config-if)# snmp trap mac-notification added  
You can verify the previous commands by entering the show mac address-table notification interface  
and the show mac address-table notification privileged EXEC commands.  
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Chapter 4 Administering the Switch  
Managing the MAC Address Table  
Adding and Removing Static Address Entries  
A static address has these characteristics:  
•
•
•
It is manually entered in the address table and must be manually removed.  
It can be a unicast or multicast address.  
It does not age and is retained when the switch restarts.  
You can add and remove static addresses and define the forwarding behavior for them. The forwarding  
behavior determines how a port that receives a packet forwards it to another port for transmission.  
Because all ports are associated with at least one VLAN, the switch acquires the VLAN ID for the  
address from the ports that you specify. You can specify a different list of destination ports for each  
source port.  
A static address in one VLAN must be a static address in other VLANs. A packet with a static address  
that arrives on a VLAN where it has not been statically entered is flooded to all ports and not learned.  
You add a static address to the address table by specifying the destination MAC address (unicast or  
multicast) and the VLAN from which it is received. Packets received with this destination address are  
forwarded to the interface specified with the interface-id option.  
Beginning in privileged EXEC mode, follow these steps to add a static address:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
mac address-table static mac-addr  
vlan vlan-id interface interface-id  
Add a static address to the MAC address table.  
•
For mac-addr, specify the destination MAC address (unicast or  
multicast) to add to the address table. Packets with this destination  
address received in the specified VLAN are forwarded to the  
specified interface.  
•
•
For vlan-id, specify the VLAN for which the packet with the  
specified MAC address is received. Valid VLAN IDs are 1 to 4094.  
For interface-id, specify the interface to which the received packet is  
forwarded. Valid interfaces include physical ports and port channels.  
For interface-id, specify the interface to which the received packet is  
forwarded. Valid interfaces include physical ports or port channels.  
For static multicast addresses, you can enter multiple interface IDs.  
For static unicast addresses, you can enter only one interface at a  
time, but you can enter the command multiple times with the same  
MAC address and VLAN ID.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show mac address-table static  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To remove static entries from the address table, use the no mac address-table static mac-addr vlan  
vlan-id [interface interface-id] global configuration command.  
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Chapter 4 Administering the Switch  
Managing the ARP Table  
This example shows how to add the static address c2f3.220a.12f4 to the MAC address table. When a  
packet is received in VLAN 4 with this MAC address as its destination address, the packets is forwarded  
to the specified interface:  
Switch(config)# mac address-table static c2f3.220a.12f4 vlan 4 interface  
gigabitethernet0/17  
Displaying Address Table Entries  
You can display the MAC address table by using one or more of the privileged EXEC commands  
described in Table 4-4:  
Commands for Displaying the MAC Address Table  
Description  
Table 4-4  
Command  
show mac address-table address  
show mac address-table aging-time  
show mac address-table count  
show mac address-table dynamic  
show mac address-table interface  
show mac address-table multicast  
show mac address-table static  
show mac address-table vlan  
Displays MAC address table information for the specified MAC address.  
Displays the aging time in all VLANs or the specified VLAN.  
Displays the number of addresses present in all VLANs or the specified VLAN.  
Displays dynamic MAC address table entries only.  
Displays the MAC address table information for the specified interface.  
Displays the Layer 2 multicast entries for all VLANs or the specified VLAN.  
Displays static MAC address table entries only.  
Displays the MAC address table information for the specified VLAN.  
Managing the ARP Table  
To communicate with a device (over Ethernet, for example), the software first must determine the 48-bit  
MAC or the local data link address of that device. The process of determining the local data link address  
from an IP address is called address resolution.  
The Address Resolution Protocol (ARP) associates a host IP address with the corresponding media or  
MAC addresses and the VLAN ID. Taking an IP address as input, ARP determines the associated MAC  
address. Once a MAC address is determined, the IP-MAC address association is stored in an ARP cache  
for rapid retrieval. Then the IP datagram is encapsulated in a link-layer frame and sent over the network.  
Encapsulation of IP datagrams and ARP requests and replies on IEEE 802 networks other than Ethernet  
is specified by the Subnetwork Access Protocol (SNAP). By default, standard Ethernet-style ARP  
encapsulation (represented by the arpa keyword) is enabled on the IP interface.  
ARP entries added manually to the table do not age and must be manually removed.  
For CLI procedures, see the Cisco IOS Release 12.1 documentation on Cisco.com.  
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C H A P T E R  
5
Configuring Switch-Based Authentication  
This chapter describes how to configure switch-based authentication on the Cisco Systems Intelligent  
Gigabit Ethernet Switch Module. This chapter consists of these sections:  
•
•
•
•
•
•
Preventing Unauthorized Access to Your Switch, page 5-1  
Protecting Access to Privileged EXEC Commands, page 5-2  
Controlling Switch Access with TACACS+, page 5-9  
Controlling Switch Access with RADIUS, page 5-16  
Configuring the Switch for Local Authentication and Authorization, page 5-31  
Configuring the Switch for Secure Shell, page 5-32  
Preventing Unauthorized Access to Your Switch  
You can prevent unauthorized users from reconfiguring your switch and viewing configuration  
information. Typically, you want network administrators to have access to your switch while you restrict  
access to users who dial from outside the network through an asynchronous port, connect from outside  
the network through a serial port, or connect through a terminal or workstation from within the local  
network.  
To prevent unauthorized access into your switch, you should configure one or more of these security  
features:  
•
At a minimum, you should configure passwords and privileges at each switch port. These passwords  
are locally stored on the switch. When users attempt to access the switch through a port or line, they  
must enter the password specified for the port or line before they can access the switch. For more  
information, see the “Protecting Access to Privileged EXEC Commands” section on page 5-2.  
•
For an additional layer of security, you can also configure username and password pairs, which are  
locally stored on the switch. These pairs are assigned to lines or interfaces and authenticate each  
user before that user can access the switch. If you have defined privilege levels, you can also assign  
a specific privilege level (with associated rights and privileges) to each username and password pair.  
For more information, see the “Configuring Username and Password Pairs” section on page 5-6.  
•
If you want to use username and password pairs, but you want to store them centrally on a server  
instead of locally, you can store them in a database on a security server. Multiple networking devices  
can then use the same database to obtain user authentication (and, if necessary, authorization)  
information. For more information, see the “Controlling Switch Access with TACACS+” section on  
page 5-9.  
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Chapter 5 Configuring Switch-Based Authentication  
Protecting Access to Privileged EXEC Commands  
Protecting Access to Privileged EXEC Commands  
A simple way of providing terminal access control in your network is to use passwords and assign  
privilege levels. Password protection restricts access to a network or network device. Privilege levels  
define what commands users can enter after they have logged into a network device.  
Note  
For complete syntax and usage information for the commands used in this section, see the Cisco IOS  
Security Command Reference for Cisco IOS Release 12.1.  
This section describes how to control access to the configuration file and privileged EXEC commands.  
It contains this configuration information:  
•
•
•
•
•
•
Default Password and Privilege Level Configuration, page 5-2  
Setting or Changing a Static Enable Password, page 5-3  
Protecting Enable and Enable Secret Passwords with Encryption, page 5-4  
Setting a Telnet Password for a Terminal Line, page 5-5  
Configuring Username and Password Pairs, page 5-6  
Configuring Multiple Privilege Levels, page 5-6  
Default Password and Privilege Level Configuration  
Table 5-1 shows the default password and privilege level configuration.  
Table 5-1  
Default Password and Privilege Levels  
Feature  
Default Setting  
Enable password and privilege level  
Enable secret password and privilege level  
Line password  
No password is defined. The default is level 15 (privileged EXEC level).  
The password is not encrypted in the configuration file.  
No password is defined. The default is level 15 (privileged EXEC level).  
The password is encrypted before it is written to the configuration file.  
No password is defined.  
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Chapter 5 Configuring Switch-Based Authentication  
Protecting Access to Privileged EXEC Commands  
Setting or Changing a Static Enable Password  
The enable password controls access to the privileged EXEC mode. Beginning in privileged EXEC  
mode, follow these steps to set or change a static enable password:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
enable password password  
Define a new password or change an existing password for access to  
privileged EXEC mode.  
By default, no password is defined.  
For password, specify a string from 1 to 25 alphanumeric characters. The  
string cannot start with a number, is case sensitive, and allows spaces but  
ignores leading spaces. It can contain the question mark (?) character if  
you precede the question mark with the key combination Crtl-v when you  
create the password; for example, to create the password abc?123, do this:  
Enter abc.  
Enter Crtl-v.  
Enter ?123.  
When the system prompts you to enter the enable password, you need not  
precede the question mark with the Ctrl-v; you can simply enter abc?123  
at the password prompt.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
The enable password is not encrypted and can be read in the switch  
configuration file.  
To remove the password, use the no enable password global configuration command.  
This example shows how to change the enable password to l1u2c3k4y5. The password is not encrypted  
and provides access to level 15 (traditional privileged EXEC mode access):  
Switch(config)# enable password l1u2c3k4y5  
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Chapter 5 Configuring Switch-Based Authentication  
Protecting Access to Privileged EXEC Commands  
Protecting Enable and Enable Secret Passwords with Encryption  
To provide an additional layer of security, particularly for passwords that cross the network or that are  
stored on a TFTP server, you can use either the enable password or enable secret global configuration  
commands. Both commands accomplish the same thing; that is, you can establish an encrypted password  
that users must enter to access privileged EXEC mode (the default) or any privilege level you specify.  
We recommend that you use the enable secret command because it uses an improved encryption  
algorithm.  
If you configure the enable secret command, it takes precedence over the enable password command;  
the two commands cannot be in effect simultaneously.  
Beginning in privileged EXEC mode, follow these steps to configure encryption for enable and enable  
secret passwords:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
enable password [level level] {password |  
encryption-type encrypted-password}  
Define a new password or change an existing password for  
access to privileged EXEC mode.  
or  
or  
enable secret [level level] {password |  
encryption-type encrypted-password}  
Define a secret password, which is saved using a  
nonreversible encryption method.  
•
(Optional) For level, the range is from 0 to 15. Level 1 is  
normal user EXEC mode privileges. The default level is  
15 (privileged EXEC mode privileges).  
•
For password, specify a string from 1 to 25  
alphanumeric characters. The string cannot start with a  
number, is case sensitive, and allows spaces but ignores  
leading spaces. By default, no password is defined.  
•
(Optional) For encryption-type, only type 5, a Cisco  
proprietary encryption algorithm, is available. If you  
specify an encryption type, you must provide an  
encrypted password—an encrypted password you copy  
from another Cisco Systems Intelligent Gigabit Ethernet  
Switch Module configuration.  
Note  
If you specify an encryption type and then enter a  
clear text password, you can not re-enter privileged  
EXEC mode. You cannot recover a lost encrypted  
password by any method.  
Step 3  
service password-encryption  
(Optional) Encrypt the password when the password is  
defined or when the configuration is written.  
Encryption prevents the password from being readable in the  
configuration file.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 5 Configuring Switch-Based Authentication  
Protecting Access to Privileged EXEC Commands  
If both the enable and enable secret passwords are defined, users must enter the enable secret password.  
Use the level keyword to define a password for a specific privilege level. After you specify the level and  
set a password, give the password only to users who need to have access at this level. Use the privilege  
level global configuration command to specify commands accessible at various levels. For more  
information, see the “Configuring Multiple Privilege Levels” section on page 5-6.  
If you enable password encryption, it applies to all passwords including username passwords,  
authentication key passwords, the privileged command password, and virtual terminal line passwords.  
To remove a password and level, use the no enable password [level level] or no enable secret [level  
level] global configuration command. To disable password encryption, use the no service  
password-encryption global configuration command.  
This example shows how to configure the encrypted password $1$FaD0$Xyti5Rkls3LoyxzS8 for  
privilege level 2:  
Switch(config)# enable secret level 2 5 $1$FaD0$Xyti5Rkls3LoyxzS8  
Setting a Telnet Password for a Terminal Line  
The switch has a default username and password, which are required when accessing the switch through  
a Telnet session. For more information, see the Cisco Intelligent Gigabit Ethernet Switch Module for the  
IBM BladeCenter Installation Guide.  
Beginning in privileged EXEC mode, follow these steps to configure your switch for Telnet access:  
Command  
Purpose  
Step 1  
enable password password  
Enter privileged EXEC mode.  
Note An enable password is configured by default. It might not be  
necessary to a password to enter privileged EXEC mode.  
Step 2  
Step 3  
configure terminal  
line vty 0 15  
Enter global configuration mode.  
Configure the number of Telnet sessions (lines), and enter line  
configuration mode.  
The default configuration is login local.  
There are 16 possible sessions on a command-capable switch. The 0  
and 15 mean that you are configuring all 16 possible Telnet sessions.  
Step 4  
password password  
Enter a Telnet password for the line or lines.  
For password, specify a string from 1 to 25 alphanumeric characters. The  
string cannot start with a number, is case sensitive, and allows spaces but  
ignores leading spaces. By default, no password is defined.  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show running-config  
Verify your entries.  
The password is listed under the command line vty 0 15.  
(Optional) Save your entries in the configuration file.  
Step 7  
copy running-config startup-config  
To remove the password, use the no password global configuration command.  
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Chapter 5 Configuring Switch-Based Authentication  
Protecting Access to Privileged EXEC Commands  
This example shows how to set the Telnet password to let45me67in89:  
Switch(config)# line vty 10  
Switch(config-line)# password let45me67in89  
Configuring Username and Password Pairs  
You can configure username and password pairs, which are locally stored on the switch. These pairs are  
assigned to lines or interfaces and authenticate each user before that user can access the switch. If you  
have defined privilege levels, you can also assign a specific privilege level (with associated rights and  
privileges) to each username and password pair.  
Beginning in privileged EXEC mode, follow these steps to establish a username-based authentication  
system that requests a login username and a password:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
username name [privilege level]  
Enter the username, privilege level, and password for each user.  
{password encryption-type password}  
•
For name, specify the user ID as one word. Spaces and quotation  
marks are not allowed.  
•
(Optional) For level, specify the privilege level the user has after  
gaining access. The range is 0 to 15. Level 15 gives privileged EXEC  
mode access. Level 1 gives user EXEC mode access.  
•
•
For encryption-type, enter 0 to specify that an unencrypted password  
will follow. Enter 7 to specify that a hidden password will follow.  
For password, specify the password the user must enter to gain access  
to the switch. The password must be from 1 to 25 characters, can  
contain embedded spaces, and must be the last option specified in the  
username command.  
Step 3  
Step 4  
line vty 0 15  
login local  
Enter line configuration mode, and configure the VTY lines (line 0 to 15).  
Enable local password checking at login time. Authentication is based on  
the username specified in Step 2.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable username authentication for a specific user, use the no username name global configuration  
command. To disable password checking and allow connections without a password, use the no login  
line configuration command.  
Configuring Multiple Privilege Levels  
By default, the software has two modes of password security: user EXEC and privileged EXEC. You  
can configure up to 16 hierarchical levels of commands for each mode. By configuring multiple  
passwords, you can allow different sets of users to have access to specified commands.  
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Chapter 5 Configuring Switch-Based Authentication  
Protecting Access to Privileged EXEC Commands  
For example, if you want many users to have access to the clear line command, you can assign it  
level 2 security and distribute the level 2 password fairly widely. But if you want more restricted access  
to the configure command, you can assign it level 3 security and distribute that password to a more  
restricted group of users.  
This section includes this configuration information:  
•
•
•
Setting the Privilege Level for a Command, page 5-7  
Changing the Default Privilege Level for Lines, page 5-8  
Logging into and Exiting a Privilege Level, page 5-8  
Setting the Privilege Level for a Command  
Beginning in privileged EXEC mode, follow these steps to set the privilege level for a command mode:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Set the privilege level for a command.  
privilege mode level level command  
•
•
•
For mode, enter configure for global configuration mode, exec for  
EXEC mode, interface for interface configuration mode, or line for  
line configuration mode.  
For level, the range is from 0 to 15. Level 1 is for normal user EXEC  
mode privileges. Level 15 is the level of access permitted by the  
enable password.  
For command, specify the command to which you want to restrict  
access.  
Step 3  
enable password level level password  
Specify the enable password for the privilege level.  
•
For level, the range is from 0 to 15. Level 1 is for normal user EXEC  
mode privileges.  
•
For password, specify a string from 1 to 25 alphanumeric characters.  
The string cannot start with a number, is case sensitive, and allows  
spaces but ignores leading spaces. By default, no password is  
defined.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
or  
The first command displays the password and access level configuration.  
The second command displays the privilege level configuration.  
show privilege  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
When you set a command to a privilege level, all commands whose syntax is a subset of that command  
are also set to that level. For example, if you set the show ip traffic command to level 15, the show  
commands and show ip commands are automatically set to privilege level 15 unless you set them  
individually to different levels.  
To return to the default privilege for a given command, use the no privilege mode level level command  
global configuration command.  
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Chapter 5 Configuring Switch-Based Authentication  
Protecting Access to Privileged EXEC Commands  
This example shows how to set the configure command to privilege level 14 and define SecretPswd14  
as the password users must enter to use level 14 commands:  
Switch(config)# privilege exec level 14 configure  
Switch(config)# enable password level 14 SecretPswd14  
Changing the Default Privilege Level for Lines  
Beginning in privileged EXEC mode, follow these steps to change the default privilege level for a line:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
line vty line  
Enter global configuration mode.  
Select the virtual terminal line on which to restrict access.  
Change the default privilege level for the line.  
privilege level level  
For level, the range is from 0 to 15. Level 1 is for normal user EXEC mode  
privileges. Level 15 is the level of access permitted by the enable  
password.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
or  
The first command displays the password and access level configuration.  
The second command displays the privilege level configuration.  
show privilege  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Users can override the privilege level you set using the privilege level line configuration command by  
logging in to the line and enabling a different privilege level. They can lower the privilege level by using  
the disable command. If users know the password to a higher privilege level, they can use that password  
to enable the higher privilege level.  
To return to the default line privilege level, use the no privilege level line configuration command.  
Logging into and Exiting a Privilege Level  
Beginning in privileged EXEC mode, follow these steps to log in to a specified privilege level and to exit  
to a specified privilege level:  
Command  
Purpose  
Step 1  
Step 2  
enable level  
Log in to a specified privilege level.  
For level, the range is 0 to 15.  
Exit to a specified privilege level.  
For level, the range is 0 to 15.  
disable level  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with TACACS+  
Controlling Switch Access with TACACS+  
This section describes how to enable and configure TACACS+, which provides detailed accounting  
information and flexible administrative control over authentication and authorization processes.  
TACACS+ is facilitated through authentication, authorization, accounting (AAA) and can be enabled  
only through AAA commands.  
Note  
For complete syntax and usage information for the commands used in this section, see the Cisco IOS  
Security Command Reference for Cisco IOS Release 12.1.  
This section contains this configuration information:  
•
•
•
•
Understanding TACACS+, page 5-9  
TACACS+ Operation, page 5-11  
Configuring TACACS+, page 5-11  
Displaying the TACACS+ Configuration, page 5-16  
Understanding TACACS+  
TACACS+ is a security application that provides centralized validation of users attempting to gain  
access to your switch. TACACS+ services are maintained in a database on a TACACS+ daemon  
typically running on a UNIX or Windows NT workstation. You should have access to and should  
configure a TACACS+ server before the configuring TACACS+ features on your switch.  
TACACS+ provides for separate and modular authentication, authorization, and accounting facilities.  
TACACS+ allows for a single access control server (the TACACS+ daemon) to provide each  
service—authentication, authorization, and accounting—independently. Each service can be tied into its  
own database to take advantage of other services available on that server or on the network, depending  
on the capabilities of the daemon.  
The goal of TACACS+ is to provide a method for managing multiple network access points from a single  
management service. Your switch can be a network access server along with other Cisco routers and  
access servers. A network access server provides connections to a single user, to a network or  
subnetwork, and to interconnected networks as shown in Figure 5-1.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with TACACS+  
Figure 5-1  
Typical TACACS+ Network Configuration  
UNIX workstation  
(TACACS+  
Catalyst 6500  
series switch  
server 1)  
171.20.10.7  
UNIX workstation  
(TACACS+  
server 2)  
171.20.10.8  
BladeCenter  
BladeCenter  
Configure the switches with the  
TACACS+ server addresses.  
Set an authentication key  
(also configure the same key on  
the TACACS+ servers).  
Enable AAA.  
Create a login authentication method list.  
Apply the list to the terminal lines.  
Create an authorization and accounting  
method list as required.  
TACACS+, administered through the AAA security services, can provide these services:  
•
Authentication—Provides complete control of authentication through login and password dialog,  
challenge and response, and messaging support.  
The authentication facility can conduct a dialog with the user (for example, after a username and  
password are provided, to challenge a user with several questions, such as home address, mother’s  
maiden name, service type, and social security number). The TACACS+ authentication service can  
also send messages to user screens. For example, a message could notify users that their passwords  
must be changed because of the company’s password aging policy.  
•
•
Authorization—Provides fine-grained control over user capabilities for the duration of the user’s  
session, including but not limited to setting autocommands, access control, session duration, or  
protocol support. You can also enforce restrictions on what commands a user can execute with the  
TACACS+ authorization feature.  
Accounting—Collects and sends information used for billing, auditing, and reporting to the  
TACACS+ daemon. Network managers can use the accounting facility to track user activity for a  
security audit or to provide information for user billing. Accounting records include user identities,  
start and stop times, executed commands (such as PPP), number of packets, and number of bytes.  
The TACACS+ protocol provides authentication between the switch and the TACACS+ daemon, and it  
ensures confidentiality because all protocol exchanges between the switch and the TACACS+ daemon  
are encrypted.  
You need a system running the TACACS+ daemon software to use TACACS+ on your switch.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with TACACS+  
TACACS+ Operation  
When a user attempts a simple ASCII login by authenticating to a switch by using TACACS+, this  
process occurs:  
1. When the connection is established, the switch contacts the TACACS+ daemon to obtain a username  
prompt to show to the user. The user enters a username, and the switch then contacts the TACACS+  
daemon to obtain a password prompt. The switch displays the password prompt to the user, the user  
enters a password, and the password is then sent to the TACACS+ daemon.  
TACACS+ allows a dialog between the daemon and the user until the daemon receives enough  
information to authenticate the user. The daemon prompts for a username and password  
combination, but can include other items, such as the user’s mother’s maiden name.  
2. The switch eventually receives one of these responses from the TACACS+ daemon:  
–
–
–
ACCEPT—The user is authenticated and service can begin. If the switch is configured to  
require authorization, authorization begins at this time.  
REJECT—The user is not authenticated. The user can be denied access or is prompted to retry  
the login sequence, depending on the TACACS+ daemon.  
ERROR—An error occurred at some time during authentication with the daemon or in the  
network connection between the daemon and the switch. If an ERROR response is received, the  
switch typically tries to use an alternative method for authenticating the user.  
–
CONTINUE—The user is prompted for additional authentication information.  
After authentication, the user undergoes an additional authorization phase if authorization has been  
enabled on the switch. Users must first successfully complete TACACS+ authentication before  
proceeding to TACACS+ authorization.  
3. If TACACS+ authorization is required, the TACACS+ daemon is again contacted, and it returns an  
ACCEPT or REJECT authorization response. If an ACCEPT response is returned, the response  
contains data in the form of attributes that direct the EXEC or NETWORK session for that user,  
determining the services that the user can access:  
–
–
Telnet, Secure Shell (SSH), rlogin, or privileged EXEC services  
Connection parameters, including the host or client IP address, access list, and user timeouts  
Configuring TACACS+  
This section describes how to configure your switch to support TACACS+. At a minimum, you must  
identify the host or hosts maintaining the TACACS+ daemon and define the method lists for TACACS+  
authentication. You can optionally define method lists for TACACS+ authorization and accounting. A  
method list defines the sequence and methods to be used to authenticate, to authorize, or to keep accounts  
on a user. You can use method lists to designate one or more security protocols to be used, thus ensuring  
a backup system if the initial method fails. The software uses the first method listed to authenticate, to  
authorize, or to keep accounts on users; if that method does not respond, the software selects the next  
method in the list. This process continues until there is successful communication with a listed method  
or the method list is exhausted.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with TACACS+  
This section contains this configuration information:  
•
•
•
•
Default TACACS+ Configuration, page 5-12  
Identifying the TACACS+ Server Host and Setting the Authentication Key, page 5-12  
Configuring TACACS+ Login Authentication, page 5-13  
Configuring TACACS+ Authorization for Privileged EXEC Access and Network Services, page  
5-15  
•
Starting TACACS+ Accounting, page 5-16  
Default TACACS+ Configuration  
TACACS+ and AAA are disabled by default.  
To prevent a lapse in security, you cannot configure TACACS+ through a network management  
application.When enabled, TACACS+ can authenticate users accessing the switch through the CLI.  
Note  
Although TACACS+ configuration is performed through the CLI, the TACACS+ server authenticates  
HTTP connections that have been configured with a privilege level of 15.  
Identifying the TACACS+ Server Host and Setting the Authentication Key  
You can configure the switch to use a single server or AAA server groups to group existing server hosts  
for authentication. You can group servers to select a subset of the configured server hosts and use them  
for a particular service. The server group is used with a global server-host list and contains the list of IP  
addresses of the selected server hosts.  
Beginning in privileged EXEC mode, follow these steps to identify the IP host or host maintaining  
TACACS+ server and optionally set the encryption key:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
tacacs-server host hostname [port  
integer] [timeout integer] [key string]  
Identify the IP host or hosts maintaining a TACACS+ server. Enter this  
command multiple times to create a list of preferred hosts. The software  
searches for hosts in the order in which you specify them.  
•
•
For hostname, specify the name or IP address of the host.  
(Optional) For port integer, specify a server port number. The default  
is port 49. The range is 1 to 65535.  
•
•
(Optional) For timeout integer, specify a time in seconds the switch  
waits for a response from the daemon before it times out and declares  
an error. The default is 5 seconds. The range is 1 to 1000 seconds.  
(Optional) For key string, specify the encryption key for encrypting  
and decrypting all traffic between the switch and the TACACS+  
daemon. You must configure the same key on the TACACS+ daemon  
for encryption to be successful.  
Step 3  
aaa new-model  
Enable AAA.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with TACACS+  
Command  
Purpose  
Step 4  
aaa group server tacacs+ group-name (Optional) Define the AAA server-group with a group name.  
This command puts the switch in a server group subconfiguration mode.  
Step 5  
server ip-address  
(Optional) Associate a particular TACACS+ server with the defined server  
group. Repeat this step for each TACACS+ server in the AAA server  
group.  
Each server in the group must be previously defined in Step 2.  
Return to privileged EXEC mode.  
Step 6  
Step 7  
Step 8  
end  
show tacacs  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To remove the specified TACACS+ server name or address, use the no tacacs-server host hostname  
global configuration command. To remove a server group from the configuration list, use the no aaa  
group server tacacs+ group-name global configuration command. To remove the IP address of a  
TACACS+ server, use the no server ip-address server group subconfiguration command.  
Configuring TACACS+ Login Authentication  
To configure AAA authentication, you define a named list of authentication methods and then apply that  
list to various interfaces. The method list defines the types of authentication to be performed and the  
sequence in which they are performed; it must be applied to a specific interface before any of the defined  
authentication methods are performed. The only exception is the default method list (which, by  
coincidence, is named default). The default method list is automatically applied to all interfaces except  
those that have a named method list explicitly defined. A defined method list overrides the default  
method list.  
A method list describes the sequence and authentication methods to be queried to authenticate a user.  
You can designate one or more security protocols to be used for authentication, thus ensuring a backup  
system for authentication in case the initial method fails. The software uses the first method listed to  
authenticate users; if that method fails to respond, the software selects the next authentication method  
in the method list. This process continues until there is successful communication with a listed  
authentication method or until all defined methods are exhausted. If authentication fails at any point in  
this cycle—meaning that the security server or local username database responds by denying the user  
access—the authentication process stops, and no other authentication methods are attempted.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with TACACS+  
Beginning in privileged EXEC mode, follow these steps to configure login authentication:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
aaa new-model  
Enter global configuration mode.  
Enable AAA.  
aaa authentication login {default |  
list-name} method1 [method2...]  
Create a login authentication method list.  
•
To create a default list that is used when a named list is not specified  
in the login authentication command, use the default keyword  
followed by the methods that are to be used in default situations. The  
default method list is automatically applied to all interfaces.  
•
•
For list-name, specify a character string to name the list you are  
creating.  
For method1..., specify the actual method the authentication  
algorithm tries. The additional methods of authentication are used  
only if the previous method returns an error, not if it fails.  
Select one of these methods:  
•
enable—Use the enable password for authentication. Before you can  
use this authentication method, you must define an enable password  
by using the enable password global configuration command.  
•
group tacacs+—Uses TACACS+ authentication. Before you can use  
this authentication method, you must configure the TACACS+ server.  
For more information, see the “Identifying the TACACS+ Server Host  
and Setting the Authentication Key” section on page 5-12.  
•
•
•
line—Use the line password for authentication. Before you can use  
this authentication method, you must define a line password. Use the  
password password line configuration command.  
local—Use the local username database for authentication. You must  
enter username information in the database. Use the username  
password global configuration command.  
local-case—Use a case-sensitive local username database for  
authentication. You must enter username information in the database  
by using the username name password global configuration  
command.  
•
none—Do not use any authentication for login.  
Step 4  
Step 5  
line [console | tty | vty] line-number  
[ending-line-number]  
Enter line configuration mode, and configure the lines to which you want  
to apply the authentication list.  
login authentication {default |  
list-name}  
Apply the authentication list to a line or set of lines.  
•
If you specify default, use the default list created with the aaa  
authentication login command.  
•
For list-name, specify the list created with the aaa authentication  
login command.  
Step 6  
Step 7  
Step 8  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with TACACS+  
To disable AAA, use the no aaa new-model global configuration command. To disable AAA  
authentication, use the no aaa authentication login {default | list-name} method1 [method2...] global  
configuration command. To either disable TACACS+ authentication for logins or to return to the default  
value, use the no login authentication {default | list-name} line configuration command.  
Configuring TACACS+ Authorization for Privileged EXEC Access and Network Services  
AAA authorization limits the services available to a user. When AAA authorization is enabled, the  
switch uses information retrieved from the user’s profile, which is located either in the local user  
database or on the security server, to configure the user’s session. The user is granted access to a  
requested service only if the information in the user profile allows it.  
You can use the aaa authorization global configuration command with the tacacs+ keyword to set  
parameters that restrict a user’s network access to privileged EXEC mode.  
The aaa authorization exec tacacs+ local command sets these authorization parameters:  
•
Use TACACS+ for privileged EXEC access authorization if authentication was performed by using  
TACACS+.  
•
Use the local database if authentication was not performed by using TACACS+.  
Note  
Authorization is bypassed for authenticated users who log in through the CLI even if authorization has  
been configured.  
Beginning in privileged EXEC mode, follow these steps to specify TACACS+ authorization for  
privileged EXEC access and network services:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
aaa authorization network tacacs+  
Configure the switch for user TACACS+ authorization for all  
network-related service requests.  
Step 3  
aaa authorization exec tacacs+  
Configure the switch for user TACACS+ authorization to determine if the  
user has privileged EXEC access.  
The exec keyword might return user profile information (such as  
autocommand information).  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable authorization, use the no aaa authorization {network | exec} method1 global configuration  
command.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Starting TACACS+ Accounting  
The AAA accounting feature tracks the services that users are accessing and the amount of network  
resources that they are consuming. When AAA accounting is enabled, the switch reports user activity to  
the TACACS+ security server in the form of accounting records. Each accounting record contains  
accounting attribute-value (AV) pairs and is stored on the security server. This data can then be analyzed  
for network management, client billing, or auditing.  
Beginning in privileged EXEC mode, follow these steps to enable TACACS+ accounting for each  
privilege level and for network services:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
aaa accounting network start-stop  
tacacs+  
Enable TACACS+ accounting for all network-related service requests.  
Step 3  
aaa accounting exec start-stop tacacs+ Enable TACACS+ accounting to send a start-record accounting notice at  
the beginning of a privileged EXEC process and a stop-record at the end.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable accounting, use the no aaa accounting {network | exec} {start-stop} method1... global  
configuration command.  
Displaying the TACACS+ Configuration  
To display TACACS+ server statistics, use the show tacacs privileged EXEC command.  
Controlling Switch Access with RADIUS  
This section describes how to enable and configure the RADIUS, which provides detailed accounting  
information and flexible administrative control over authentication and authorization processes.  
RADIUS is facilitated through AAA and can be enabled only through AAA commands.  
Note  
For complete syntax and usage information for the commands used in this section, see the Cisco IOS  
Security Command Reference for Cisco IOS Release 12.1.  
This section contains this configuration information:  
•
•
•
•
Understanding RADIUS, page 5-17  
RADIUS Operation, page 5-18  
Configuring RADIUS, page 5-19  
Displaying the RADIUS Configuration, page 5-30  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Understanding RADIUS  
RADIUS is a distributed client/server system that secures networks against unauthorized access.  
RADIUS clients run on supported Cisco routers and switches. Clients send authentication requests to a  
central RADIUS server, which contains all user authentication and network service access information.  
The RADIUS host is normally a multiuser system running RADIUS server software from Cisco (Cisco  
Secure Access Control Server version 3.0), Livingston, Merit, Microsoft, or another software provider.  
For more information, see the RADIUS server documentation.  
Use RADIUS in these network environments that require access security:  
•
Networks with multiple-vendor access servers, each supporting RADIUS. For example, access  
servers from several vendors use a single RADIUS server-based security database. In an IP-based  
network with multiple vendors’ access servers, dial-in users are authenticated through a RADIUS  
server that has been customized to work with the Kerberos security system.  
•
•
•
Turnkey network security environments in which applications support the RADIUS protocol, such  
as in an access environment that uses a smart card access control system. In one case, RADIUS has  
been used with Enigma’s security cards to validates users and to grant access to network resources.  
Networks already using RADIUS. You can add a Cisco switch containing a RADIUS client to the  
network. This might be the first step when you make a transition to a TACACS+ server. See  
Figure 5-2 on page 5-18.  
Network in which the user must only access a single service. Using RADIUS, you can control user  
access to a single host, to a single utility such as Telnet, or to the network through a protocol such  
as IEEE 802.1X. For more information about this protocol, see Chapter 6, “Configuring IEEE  
802.1x Port-Based Authentication.”  
•
Networks that require resource accounting. You can use RADIUS accounting independently of  
RADIUS authentication or authorization. The RADIUS accounting functions allow data to be sent  
at the start and end of services, showing the amount of resources (such as time, packets, bytes, and  
so forth) used during the session. An Internet service provider might use a freeware-based version  
of RADIUS access control and accounting software to meet special security and billing needs.  
RADIUS is not suitable in these network security situations:  
•
•
•
Multiprotocol access environments. RADIUS does not support AppleTalk Remote Access (ARA),  
NetBIOS Frame Control Protocol (NBFCP), NetWare Asynchronous Services Interface (NASI), or  
X.25 PAD connections.  
Switch-to-switch or router-to-router situations. RADIUS does not provide two-way authentication.  
RADIUS can be used to authenticate from one device to a non-Cisco device if the non-Cisco device  
requires authentication.  
Networks using a variety of services. RADIUS generally binds a user to one service model.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Figure 5-2  
Transitioning from RADIUS to TACACS+ Services  
Catalyst 2950, 2955,  
or 3550 switch  
Remote  
PC  
BladeCenter  
RADIUS Operation  
When a user attempts to log in and authenticate to a switch that is access controlled by a RADIUS server,  
these events occur:  
1. The user is prompted to enter a username and password.  
2. The username and encrypted password are sent over the network to the RADIUS server.  
3. The user receives one of these responses from the RADIUS server:  
a. ACCEPT—The user is authenticated.  
b. REJECT—The user is either not authenticated and is prompted to re-enter the username and  
password, or access is denied.  
c. CHALLENGE—A challenge requires additional data from the user.  
d. CHALLENGE PASSWORD—A response requests the user to select a new password.  
The ACCEPT or REJECT response is bundled with additional data that is used for privileged EXEC or  
network authorization. Users must first successfully complete RADIUS authentication before  
proceeding to RADIUS authorization, if it is enabled. The additional data included with the ACCEPT or  
REJECT packets includes these items:  
•
•
Telnet, SSH, rlogin, or privileged EXEC services  
Connection parameters, including the host or client IP address, access list, and user timeouts  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Configuring RADIUS  
This section describes how to configure your switch to support RADIUS. At a minimum, you must  
identify the host or hosts that run the RADIUS server software and define the method lists for RADIUS  
authentication. You can optionally define method lists for RADIUS authorization and accounting.  
A method list defines the sequence and methods to be used to authenticate, to authorize, or to keep  
accounts on a user. You can use method lists to designate one or more security protocols to be used (such  
as TACACS+ or local username lookup), thus ensuring a backup system if the initial method fails. The  
software uses the first method listed to authenticate, to authorize, or to keep accounts on users; if that  
method does not respond, the software selects the next method in the list. This process continues until  
there is successful communication with a listed method or the method list is exhausted.  
You should have access to and should configure a RADIUS server before configuring RADIUS features  
on your switch.  
This section contains this configuration information:  
•
•
•
•
•
Default RADIUS Configuration, page 5-19  
Identifying the RADIUS Server Host, page 5-19 (required)  
Configuring RADIUS Login Authentication, page 5-22 (required)  
Defining AAA Server Groups, page 5-24 (optional)  
Configuring RADIUS Authorization for User Privileged Access and Network Services, page 5-26  
(optional)  
•
•
•
•
Starting RADIUS Accounting, page 5-27 (optional)  
Configuring Settings for All RADIUS Servers, page 5-28 (optional)  
Configuring the Switch to Use Vendor-Specific RADIUS Attributes, page 5-28 (optional)  
Configuring the Switch for Vendor-Proprietary RADIUS Server Communication, page 5-29  
(optional)  
Default RADIUS Configuration  
RADIUS and AAA are disabled by default.  
To prevent a lapse in security, you cannot configure RADIUS through a network management  
application. When enabled, RADIUS can authenticate users accessing the switch through the CLI.  
Identifying the RADIUS Server Host  
Switch-to-RADIUS-server communication involves several components:  
•
•
•
•
•
•
Host name or IP address  
Authentication destination port  
Accounting destination port  
Key string  
Timeout period  
Retransmission value  
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Controlling Switch Access with RADIUS  
You identify RADIUS security servers by their host name or IP address, host name and specific UDP  
port numbers, or their IP address and specific UDP port numbers. The combination of the IP address and  
the UDP port number creates a unique identifier, allowing different ports to be individually defined as  
RADIUS hosts providing a specific AAA service. This unique identifier enables RADIUS requests to be  
sent to multiple UDP ports on a server at the same IP address.  
If two different host entries on the same RADIUS server are configured for the same service—for  
example, accounting—the second host entry configured acts as a fail-over backup to the first one. Using  
this example, if the first host entry fails to provide accounting services, the switch tries the second host  
entry configured on the same device for accounting services. (The RADIUS host entries are tried in the  
order that they are configured.)  
A RADIUS server and the switch use a shared secret text string to encrypt passwords and exchange  
responses. To configure RADIUS to use the AAA security commands, you must specify the host running  
the RADIUS server daemon and a secret text (key) string that it shares with the switch.  
The timeout, retransmission, and encryption key values can be configured globally for all RADIUS  
servers, on a per-server basis, or in some combination of global and per-server settings. To apply these  
settings globally to all RADIUS servers communicating with the switch, use the three unique global  
configuration commands: radius-server timeout, radius-server retransmit, and radius-server key.  
To apply these values on a specific RADIUS server, use the radius-server host global configuration  
command.  
Note  
If you configure both global and per-server functions (timeout, retransmission, and key commands) on  
the switch, the per-server timer, retransmission, and key value commands override global timer,  
retransmission, and key value commands. For information on configuring these settings on all RADIUS  
servers, see the “Configuring Settings for All RADIUS Servers” section on page 5-28.  
You can configure the switch to use AAA server groups to group existing server hosts for authentication.  
For more information, see the “Defining AAA Server Groups” section on page 5-24.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Beginning in privileged EXEC mode, follow these steps to configure per-server RADIUS server  
communication. This procedure is required.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
radius-server host {hostname |  
ip-address} [auth-port port-number]  
[acct-port port-number] [timeout  
seconds] [retransmit retries] [key  
string]  
Specify the IP address or host name of the remote RADIUS server host.  
•
•
•
(Optional) For auth-port port-number, specify the UDP destination  
port for authentication requests.  
(Optional) For acct-port port-number, specify the UDP destination  
port for accounting requests.  
(Optional) For timeout seconds, specify the time interval that the  
switch waits for the RADIUS server to reply before resending. The  
range is 1 to 1000. This setting overrides the radius-server timeout  
global configuration command setting. If no timeout is set with the  
radius-server host command, the setting of the radius-server  
timeout command is used.  
•
(Optional) For retransmit retries, specify the number of times a  
RADIUS request is resent to a server if that server is not responding  
or responding slowly. The range is 1 to 1000. If no retransmit value is  
set with the radius-server host command, the setting of the  
radius-server retransmit global configuration command is used.  
•
(Optional) For key string, specify the authentication and encryption  
key used between the switch and the RADIUS daemon running on the  
RADIUS server.  
Note  
The key is a text string that must match the encryption key used  
on the RADIUS server. Always configure the key as the last item  
in the radius-server host command. Leading spaces are ignored,  
but spaces within and at the end of the key are used. If you use  
spaces in your key, do not enclose the key in quotation marks  
unless the quotation marks are part of the key.  
To configure the switch to recognize more than one host entry associated  
with a single IP address, enter this command as many times as necessary,  
making sure that each UDP port number is different. The switch software  
searches for hosts in the order in which you specify them. Set the timeout,  
retransmit, and encryption key values to use with the specific RADIUS  
host.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To remove the specified RADIUS server, use the no radius-server host hostname | ip-address global  
configuration command.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
This example shows how to configure one RADIUS server to be used for authentication and another to  
be used for accounting:  
Switch(config)# radius-server host 172.29.36.49 auth-port 1612 key rad1  
Switch(config)# radius-server host 172.20.36.50 acct-port 1618 key rad2  
This example shows how to configure host1 as the RADIUS server and to use the default ports for both  
authentication and accounting:  
Switch(config)# radius-server host host1  
Note  
You also need to configure some settings on the RADIUS server. These settings include the IP address  
of the switch and the key string to be shared by both the server and the switch. For more information,  
see the RADIUS server documentation.  
Configuring RADIUS Login Authentication  
To configure AAA authentication, you define a named list of authentication methods and then apply that  
list to various interfaces. The method list defines the types of authentication to be performed and the  
sequence in which they are performed; it must be applied to a specific interface before any of the defined  
authentication methods are performed. The only exception is the default method list (which, by  
coincidence, is named default). The default method list is automatically applied to all interfaces except  
those that have a named method list explicitly defined.  
A method list describes the sequence and authentication methods to be queried to authenticate a user.  
You can designate one or more security protocols to be used for authentication, thus ensuring a backup  
system for authentication in case the initial method fails. The software uses the first method listed to  
authenticate users; if that method fails to respond, the software selects the next authentication method  
in the method list. This process continues until there is successful communication with a listed  
authentication method or until all defined methods are exhausted. If authentication fails at any point in  
this cycle—meaning that the security server or local username database responds by denying the user  
access—the authentication process stops, and no other authentication methods are attempted.  
Beginning in privileged EXEC mode, follow these steps to configure login authentication. This  
procedure is required.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
aaa new-model  
Enter global configuration mode.  
Enable AAA.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Command  
Purpose  
Create a login authentication method list.  
Step 3  
aaa authentication login {default |  
list-name} method1 [method2...]  
•
To create a default list that is used when a named list is not specified  
in the login authentication command, use the default keyword  
followed by the methods that are to be used in default situations. The  
default method list is automatically applied to all interfaces.  
•
•
For list-name, specify a character string to name the list you are  
creating.  
For method1..., specify the actual method the authentication  
algorithm tries. The additional methods of authentication are used  
only if the previous method returns an error, not if it fails.  
Select one of these methods:  
–
enable—Use the enable password for authentication. Before you  
can use this authentication method, you must define an enable  
password by using the enable password global configuration  
command.  
–
group radius—Use RADIUS authentication. Before you can use  
this authentication method, you must configure the RADIUS  
server. For more information, see the “Identifying the RADIUS  
Server Host” section on page 5-19.  
–
–
–
line—Use the line password for authentication. Before you can  
use this authentication method, you must define a line password.  
Use the password password line configuration command.  
local—Use the local username database for authentication. You  
must enter username information in the database. Use the  
username name password global configuration command.  
local-case—Use a case-sensitive local username database for  
authentication. You must enter username information in the  
database by using the username password global configuration  
command.  
–
none—Do not use any authentication for login.  
Step 4  
Step 5  
line [console | tty | vty] line-number  
[ending-line-number]  
Enter line configuration mode, and configure the lines to which you want  
to apply the authentication list.  
login authentication {default |  
list-name}  
Apply the authentication list to a line or set of lines.  
•
If you specify default, use the default list created with the aaa  
authentication login command.  
•
For list-name, specify the list created with the aaa authentication  
login command.  
Step 6  
Step 7  
Step 8  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
To disable AAA, use the no aaa new-model global configuration command. To disable AAA  
authentication, use the no aaa authentication login {default | list-name} method1 [method2...] global  
configuration command. To either disable RADIUS authentication for logins or to return to the default  
value, use the no login authentication {default | list-name} line configuration command.  
Defining AAA Server Groups  
You can configure the switch to use AAA server groups to group existing server hosts for authentication.  
You select a subset of the configured server hosts and use them for a particular service. The server group  
is used with a global server-host list, which lists the IP addresses of the selected server hosts.  
Server groups also can include multiple host entries for the same server if each entry has a unique  
identifier (the combination of the IP address and UDP port number), allowing different ports to be  
individually defined as RADIUS hosts providing a specific AAA service. If you configure two different  
host entries on the same RADIUS server for the same service, (for example, accounting), the second  
configured host entry acts as a fail-over backup to the first one.  
You use the server group server configuration command to associate a particular server with a defined  
group server. You can either identify the server by its IP address or identify multiple host instances or  
entries by using the optional auth-port and acct-port keywords.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Beginning in privileged EXEC mode, follow these steps to define the AAA server group and associate  
a particular RADIUS server with it:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
radius-server host {hostname |  
ip-address} [auth-port port-number]  
[acct-port port-number] [timeout  
seconds] [retransmit retries] [key  
string]  
Specify the IP address or host name of the remote RADIUS server host.  
•
•
•
(Optional) For auth-port port-number, specify the UDP destination  
port for authentication requests.  
(Optional) For acct-port port-number, specify the UDP destination  
port for accounting requests.  
(Optional) For timeout seconds, specify the time interval that the  
switch waits for the RADIUS server to reply before resending. The  
range is 1 to 1000. This setting overrides the radius-server timeout  
global configuration command setting. If no timeout is set with the  
radius-server host command, the setting of the radius-server  
timeout command is used.  
•
(Optional) For retransmit retries, specify the number of times a  
RADIUS request is resent to a server if that server is not responding  
or responding slowly. The range is 1 to 1000. If no retransmit value is  
set with the radius-server host command, the setting of the  
radius-server retransmit global configuration command is used.  
•
(Optional) For key string, specify the authentication and encryption  
key used between the switch and the RADIUS daemon running on the  
RADIUS server.  
Note  
The key is a text string that must match the encryption key used  
on the RADIUS server. Always configure the key as the last item  
in the radius-server host command. Leading spaces are ignored,  
but spaces within and at the end of the key are used. If you use  
spaces in your key, do not enclose the key in quotation marks  
unless the quotation marks are part of the key.  
To configure the switch to recognize more than one host entry associated  
with a single IP address, enter this command as many times as necessary,  
making sure that each UDP port number is different. The switch software  
searches for hosts in the order in which you specify them. Set the timeout,  
retransmit, and encryption key values to use with the specific RADIUS  
host.  
Step 3  
Step 4  
aaa new-model  
Enable AAA.  
aaa group server radius group-name  
Define the AAA server-group with a group name.  
This command puts the switch in a server group configuration mode.  
Step 5  
server ip-address  
Associate a particular RADIUS server with the defined server group.  
Repeat this step for each RADIUS server in the AAA server group.  
Each server in the group must be previously defined in Step 2.  
Return to privileged EXEC mode.  
Step 6  
Step 7  
end  
show running-config  
Verify your entries.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Command  
Purpose  
Step 8  
Step 9  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Enable RADIUS login authentication. See the “Configuring RADIUS  
Login Authentication” section on page 5-22.  
To remove the specified RADIUS server, use the no radius-server host hostname | ip-address global  
configuration command. To remove a server group from the configuration list, use the no aaa group  
server radius group-name global configuration command. To remove the IP address of a RADIUS  
server, use the no server ip-address server group configuration command.  
In this example, the switch is configured to recognize two different RADIUS group servers (group1 and  
group2). Group1 has two different host entries on the same RADIUS server configured for the same  
services. The second host entry acts as a fail-over backup to the first entry.  
Switch(config)# radius-server host 172.20.0.1 auth-port 1000 acct-port 1001  
Switch(config)# radius-server host 172.10.0.1 auth-port 1645 acct-port 1646  
Switch(config)# aaa new-model  
Switch(config)# aaa group server radius group1  
Switch(config-sg-radius)# server 172.20.0.1 auth-port 1000 acct-port 1001  
Switch(config-sg-radius)# exit  
Switch(config)# aaa group server radius group2  
Switch(config-sg-radius)# server 172.20.0.1 auth-port 2000 acct-port 2001  
Switch(config-sg-radius)# exit  
Configuring RADIUS Authorization for User Privileged Access and Network Services  
AAA authorization limits the services available to a user. When AAA authorization is enabled, the  
switch uses information retrieved from the user’s profile, which is in the local user database or on the  
security server, to configure the user’s session. The user is granted access to a requested service only if  
the information in the user profile allows it.  
You can use the aaa authorization global configuration command with the radius keyword to set  
parameters that restrict a user’s network access to privileged EXEC mode.  
The aaa authorization exec radius local command sets these authorization parameters:  
•
Use RADIUS for privileged EXEC access authorization if authentication was performed by using  
RADIUS.  
•
Use the local database if authentication was not performed by using RADIUS.  
Note  
Authorization is bypassed for authenticated users who log in through the CLI even if authorization has  
been configured.  
Beginning in privileged EXEC mode, follow these steps to specify RADIUS authorization for privileged  
EXEC access and network services:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
aaa authorization network radius  
Configure the switch for user RADIUS authorization for all  
network-related service requests.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Command  
Purpose  
Step 3  
aaa authorization exec radius  
Configure the switch for user RADIUS authorization to determine if the  
user has privileged EXEC access.  
The exec keyword might return user profile information (such as  
autocommand information).  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable authorization, use the no aaa authorization {network | exec} method1 global configuration  
command.  
Starting RADIUS Accounting  
The AAA accounting feature tracks the services that users are accessing and the amount of network  
resources that they are consuming. When AAA accounting is enabled, the switch reports user activity to  
the RADIUS security server in the form of accounting records. Each accounting record contains  
accounting attribute-value (AV) pairs and is stored on the security server. This data can then be analyzed  
for network management, client billing, or auditing.  
Beginning in privileged EXEC mode, follow these steps to enable RADIUS accounting for each Cisco  
IOS privilege level and for network services:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
aaa accounting network start-stop  
radius  
Enable RADIUS accounting for all network-related service requests.  
Step 3  
aaa accounting exec start-stop radius  
Enable RADIUS accounting to send a start-record accounting notice at  
the beginning of a privileged EXEC process and a stop-record at the end.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable accounting, use the no aaa accounting {network | exec} {start-stop} method1... global  
configuration command.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Configuring Settings for All RADIUS Servers  
Beginning in privileged EXEC mode, follow these steps to configure global communication settings  
between the switch and all RADIUS servers:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
radius-server key string  
Specify the shared secret text string used between the switch and all  
RADIUS servers.  
Note  
The key is a text string that must match the encryption key used on  
the RADIUS server. Leading spaces are ignored, but spaces within  
and at the end of the key are used. If you use spaces in your key, do  
not enclose the key in quotation marks unless the quotation marks  
are part of the key.  
Step 3  
Step 4  
radius-server retransmit retries  
radius-server timeout seconds  
Specify the number of times the switch sends each RADIUS request to the  
server before giving up. The default is 3; the range 1 to 1000.  
Specify the number of seconds a switch waits for a reply to a RADIUS  
request before resending the request. The default is 5 seconds; the range is  
1 to 1000.  
Step 5  
radius-server deadtime minutes  
Specify the number of minutes a RADIUS server, which is not responding  
to authentication requests, to be skipped, thus avoiding the wait for the  
request to timeout before trying the next configured server. The default is  
0; the range is 1 to 1440 minutes.  
Step 6  
Step 7  
Step 8  
end  
Return to privileged EXEC mode.  
Verify your settings.  
show running-config  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To return to the default setting for the retransmit, timeout, and deadtime, use the no forms of these  
commands.  
Configuring the Switch to Use Vendor-Specific RADIUS Attributes  
The Internet Engineering Task Force (IETF) draft standard specifies a method for communicating  
vendor-specific information between the switch and the RADIUS server by using the vendor-specific  
attribute (attribute 26). Vendor-specific attributes (VSAs) allow vendors to support their own extended  
attributes not suitable for general use. The Cisco RADIUS implementation supports one vendor-specific  
option by using the format recommended in the specification. Cisco’s vendor-ID is 9, and the supported  
option has vendor-type 1, which is named cisco-avpair. The value is a string with this format:  
protocol : attribute sep value *  
Protocol is a value of the Cisco protocol attribute for a particular type of authorization. Attribute and  
value are an appropriate attribute-value (AV) pair defined in the Cisco TACACS+ specification, and sep  
is = for mandatory attributes and is * for optional attributes. The full set of features available for  
TACACS+ authorization can then be used for RADIUS.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
For example, this AV pair activates Cisco’s multiple named ip address pools feature during IP  
authorization (during PPP’s IPCP address assignment):  
cisco-avpair= ”ip:addr-pool=first“  
This example shows how to provide a user logging in from a switch with immediate access to privileged  
EXEC commands:  
cisco-avpair= ”shell:priv-lvl=15“  
This example shows how to specify an authorized VLAN in the RADIUS server database:  
cisco-avpair= ”tunnel-type(#64)=VLAN(13)”  
cisco-avpair= ”tunnel-medium-type(#65)=802 media(6)”  
cisco-avpair= ”tunnel-private-group-ID(#81)=vlanid”  
Other vendors have their own unique vendor-IDs, options, and associated VSAs. For more information  
about vendor-IDs and VSAs, see RFC 2138, “Remote Authentication Dial-In User Service (RADIUS).”  
Beginning in privileged EXEC mode, follow these steps to configure the switch to recognize and use  
VSAs:  
Command  
configure terminal  
radius-server vsa send [accounting | Enable the switch to recognize and use VSAs as defined by RADIUS IETF  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
authentication]  
attribute 26.  
•
•
(Optional) Use the accounting keyword to limit the set of recognized  
vendor-specific attributes to only accounting attributes.  
(Optional) Use the authentication keyword to limit the set of  
recognized vendor-specific attributes to only authentication attributes.  
If you enter this command without keywords, both accounting and  
authentication vendor-specific attributes are used.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your settings.  
show running-config  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
For a complete list of RADIUS attributes or more information about vendor-specific attribute 26, see the  
“RADIUS Attributes” appendix in the Cisco IOS Security Configuration Guide for Cisco IOS Release  
12.1.  
Configuring the Switch for Vendor-Proprietary RADIUS Server Communication  
Although an IETF draft standard for RADIUS specifies a method for communicating vendor-proprietary  
information between the switch and the RADIUS server, some vendors have extended the RADIUS  
attribute set in a unique way. Cisco IOS software supports a subset of vendor-proprietary RADIUS  
attributes.  
As mentioned earlier, to configure RADIUS (whether vendor-proprietary or IETF draft-compliant), you  
must specify the host running the RADIUS server daemon and the secret text string it shares with the  
switch. You specify the RADIUS host and secret text string by using the radius-server global  
configuration commands.  
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Chapter 5 Configuring Switch-Based Authentication  
Controlling Switch Access with RADIUS  
Beginning in privileged EXEC mode, follow these steps to specify a vendor-proprietary RADIUS server  
host and a shared secret text string:  
Command  
configure terminal  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
radius-server host {hostname | ip-address} non-standard Specify the IP address or host name of the remote  
RADIUS server host and identify that it is using a  
vendor-proprietary implementation of RADIUS.  
Step 3  
radius-server key string  
Specify the shared secret text string used between the  
switch and the vendor-proprietary RADIUS server.  
The switch and the RADIUS server use this text  
string to encrypt passwords and exchange responses.  
Note  
The key is a text string that must match the  
encryption key used on the RADIUS server.  
Leading spaces are ignored, but spaces within  
and at the end of the key are used. If you use  
spaces in your key, do not enclose the key in  
quotation marks unless the quotation marks  
are part of the key.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your settings.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To delete the vendor-proprietary RADIUS host, use the no radius-server host {hostname | ip-address}  
non-standard global configuration command. To disable the key, use the no radius-server key global  
configuration command.  
This example shows how to specify a vendor-proprietary RADIUS host and to use a secret key of rad124  
between the switch and the server:  
Switch(config)# radius-server host 172.20.30.15 nonstandard  
Switch(config)# radius-server key rad124  
Displaying the RADIUS Configuration  
To display the RADIUS configuration, use the show running-config privileged EXEC command.  
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Chapter 5 Configuring Switch-Based Authentication  
Configuring the Switch for Local Authentication and Authorization  
Configuring the Switch for Local Authentication and  
Authorization  
You can configure AAA to operate without a server by setting the switch to implement AAA in local  
mode. The switch then handles authentication and authorization. No accounting is available in this  
configuration.  
Beginning in privileged EXEC mode, follow these steps to configure the switch for local AAA:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
aaa new-model  
Enter global configuration mode.  
Enable AAA.  
aaa authentication login default local Set the login authentication to use the local username database. The  
default keyword applies the local user database authentication to all  
interfaces.  
Step 4  
Step 5  
Step 6  
aaa authorization exec local  
aaa authorization network local  
username name [privilege level]  
Configure user AAA authorization to determine if the user is allowed to  
run an EXEC shell by checking the local database.  
Configure user AAA authorization for all network-related service  
requests.  
Enter the local database, and establish a username-based authentication  
{password encryption-type password} system.  
Repeat this command for each user.  
•
•
For name, specify the user ID as one word. Spaces and quotation  
marks are not allowed.  
(Optional) For level, specify the privilege level the user has after  
gaining access. The range is 0 to 15. Level 15 gives privileged EXEC  
mode access. Level 0 gives user EXEC mode access.  
•
•
For encryption-type, enter 0 to specify that an unencrypted password  
follows. Enter 7 to specify that a hidden password follows.  
For password, specify the password the user must enter to gain access  
to the switch. The password must be from 1 to 25 characters, can  
contain embedded spaces, and must be the last option specified in the  
username command.  
Step 7  
Step 8  
Step 9  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable AAA, use the no aaa new-model global configuration command. To disable authorization,  
use the no aaa authorization {network | exec} method1 global configuration command.  
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Chapter 5 Configuring Switch-Based Authentication  
Configuring the Switch for Secure Shell  
Configuring the Switch for Secure Shell  
This section describes how to configure the Secure Shell (SSH) feature. SSH is a cryptographic security  
feature that is subject to export restrictions. To use this feature, the cryptographic (encrypted) software  
image must be installed on your switch. You must obtain authorization to use this feature and to  
download the cryptographic software files from ibm.com. For more information, see the release notes  
for this release.  
This section contains this information:  
•
•
•
Understanding SSH, page 5-32  
Configuring SSH, page 5-33  
Displaying the SSH Configuration and Status, page 5-36  
For SSH configuration examples, see the “SSH Configuration Examples” section in the “Configuring  
Secure Shell” chapter of the Cisco IOS Security Configuration Guide, Cisco IOS Release 12.2, at this  
URL:  
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fsecur_c/fothersf/  
scfssh.htm  
Note  
For complete syntax and usage information for the commands used in this section, see the command  
reference for this release and the command reference for Cisco IOS Release 12.2 at this URL:  
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/index.htm.  
Understanding SSH  
SSH is a protocol that provides a secure, remote connection to a device. SSH provides more security for  
remote connections than Telnet does by providing strong encryption when a device is authenticated. This  
software release supports SSH version 1 (SSHv1) and SSH version 2 (SSHv2).  
This section consists of these topics:  
•
•
SSH Servers, Integrated Clients, and Supported Versions, page 5-32  
Limitations, page 5-33  
SSH Servers, Integrated Clients, and Supported Versions  
The SSH feature has an SSH server and an SSH integrated client, which are applications that run on the  
switch. You can use an SSH client to connect to a switch running the SSH server. The SSH server works  
with the SSH client supported in this release and with non-Cisco SSH clients. The SSH client also works  
with the SSH server supported in this release and with non-Cisco SSH servers.  
The switch supports an SSHv1 or an SSHv2 server.  
The switch supports an SSHv1 client.  
SSH supports the Data Encryption Standard (DES) encryption algorithm, the Triple DES (3DES)  
encryption algorithm, and password-based user authentication.  
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Chapter 5 Configuring Switch-Based Authentication  
Configuring the Switch for Secure Shell  
SSH also supports these user authentication methods:  
•
•
•
TACACS+ (for more information, see the “Controlling Switch Access with TACACS+” section on  
page 5-9)  
RADIUS (for more information, see the “Controlling Switch Access with RADIUS” section on  
page 5-16)  
Local authentication and authorization (for more information, see the “Configuring the Switch for  
Local Authentication and Authorization” section on page 5-31)  
Note  
This software release does not support IP Security (IPSec).  
Limitations  
These limitations apply to SSH:  
•
•
•
The switch supports Rivest, Shamir, and Adelman (RSA) authentication.  
SSH supports only the execution-shell application.  
The SSH server and the SSH client are supported only on DES (56-bit) and 3DES (168-bit) data  
encryption software.  
•
The switch does not support the Advanced Encryption Standard (AES) symmetric encryption  
algorithm.  
Configuring SSH  
This section has this configuration information:  
•
•
•
Configuration Guidelines, page 5-33  
Cryptographic Software Image Guidelines, page 5-34  
Configuring the SSH Server, page 5-35 (required only if you are configuring the switch as an SSH  
server)  
Before configuring SSH, download the cryptographic software image from www.ibm.com/support, as  
described in the “Setting Up the Switch to Run SSH” section on page 5-34. For information about  
configuring SSH and displaying SSH settings, see the “Configuring Secure Shell” section in the Cisco  
IOS Security Configuration Guide for Cisco IOS Release 12.2.  
Configuration Guidelines  
Follow these guidelines when configuring the switch as an SSH server or SSH client:  
•
•
An RSA key pair generated by a SSHv1 server can be used by an SSHv2 server, and the reverse.  
If you get CLI error messages after entering the crypto key generate rsa global configuration  
command, an RSA key pair has not been generated. Reconfigure the host name and domain, and then  
enter the crypto key generate rsa command. For more information, see the “Setting Up the Switch  
to Run SSH” section on page 5-34.  
•
When generating the RSA key pair, the message “No host name specified” might appear. If it does,  
you must configure a host name by using the hostname global configuration command.  
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Chapter 5 Configuring Switch-Based Authentication  
Configuring the Switch for Secure Shell  
•
•
When generating the RSA key pair, the message “No domain specified” might appear. If it does,  
you must configure an IP domain name by using the ip domain-name global configuration  
command.  
When configuring the local authentication and authorization authentication method, make sure that  
AAA is disabled on the console.  
Cryptographic Software Image Guidelines  
The SSH feature uses a large amount of switch memory, which limits the number of VLANs and trunk  
ports that you can configure on the switch. Before you download the cryptographic software image, your  
switch configuration must meet these conditions:  
•
The number of trunk ports multiplied by the number of VLANs on the switch must be less than or  
equal to 256. These are examples of switch configurations that meet this condition:  
–
–
If the switch has 4 trunk ports, it can have up to 64 VLANs.  
If the switch has 32 VLANs, it can have up to 8 trunk ports.  
Setting Up the Switch to Run SSH  
To access the cryptographic version of the Cisco Systems Intelligent Gigabit Ethernet Switch Module  
software, follow these steps:  
1. Go to the IBM web site:  
http://www.ibm.com/support.  
2. Click Support & downloads > Downloads and drivers > BladeCenter (Blades) > BladeCenter  
chassis Hardware only > Firmware.  
3. Click Cisco Systems Intelligent Gigabit Ethernet Switch Module Firmware update - IBM  
BladeCenter.  
4. Find and click the Crypto Code link.  
5. Register and log in with your IBM ID and password.  
6. Find and click the latest level of cryptographic version software.  
7. Click Download now to save the file to your computer.  
8. From your computer you can ftp the file to your switch. This process is described in the switch  
command reference using the archive download privileged EXEC command.  
For information about configuring SSH and displaying SSH settings, see the “Configuring Secure Shell”  
section in the Cisco IOS Security Configuration Guide for Cisco IOS Release 12.2.  
Follow these steps to set up your switch to run SSH:  
1. Download the cryptographic software image from Cisco.com. This step is required. For more  
information, see the release notes for this release.  
2. Configure a host name and IP domain name for the switch. Follow this procedure only if you are  
configuring the switch as an SSH server.  
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Chapter 5 Configuring Switch-Based Authentication  
Configuring the Switch for Secure Shell  
3. Generate an RSA key pair for the switch, which automatically enables SSH. Follow this procedure  
only if you are configuring the switch as an SSH server.  
4. Configure user authentication for local or remote access. This step is required. For more  
information, see the “Configuring the Switch for Local Authentication and Authorization” section  
on page 5-31.  
Beginning in privileged EXEC mode, follow these steps to configure a host name and an IP domain name  
and to generate an RSA key pair. This procedure is required if you are configuring the switch as an SSH  
server.  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
configure terminal  
Enter global configuration mode.  
hostname hostname  
Configure a host name for your switch.  
Configure a host domain for your switch.  
ip domain-name domain_name  
crypto key generate rsa  
Enable the SSH server for local and remote authentication on the switch  
and generate an RSA key pair.  
We recommend that a minimum modulus size of 1024 bits.  
When you generate RSA keys, you are prompted to enter a modulus  
length. A longer modulus length might be more secure, but it takes longer  
to generate and to use.  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show ip ssh  
Show the version and configuration information for your SSH server.  
or  
show ssh  
Show the status of the SSH server on the switch.  
(Optional) Save your entries in the configuration file.  
Step 7  
copy running-config startup-config  
To delete the RSA key pair, use the crypto key zeroize rsa global configuration command. After the  
RSA key pair is deleted, the SSH server is automatically disabled.  
Configuring the SSH Server  
Beginning in privileged EXEC mode, follow these steps to configure the SSH server:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
ip ssh version [1 | 2]  
Enter global configuration mode.  
(Optional) Configure the switch to run SSH version 1 or SSH version 2.  
•
•
1—Configure the switch to run SSH version 1.  
2—Configure the switch to run SSH version 2.  
If you do not enter this command or do not specify a keyword, the SSH  
server selects the latest SSH version supported by the SSH client. For  
example, if the SSH client sports SSHv1 and SSHv2, the SSH server  
selects SSHv2.  
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Chapter 5 Configuring Switch-Based Authentication  
Configuring the Switch for Secure Shell  
Command  
Purpose  
Configure the SSH control parameters:  
Step 3  
ip ssh {timeout seconds |  
authentication-retries number}  
•
Specify the time-out value in seconds; the default is 120 seconds. The  
range is 0 to 120 seconds. This parameter applies to the SSH  
negotiation phase. After the connection is established, the switch uses  
the default time-out values of the CLI-based sessions.  
By default, up to five simultaneous, encrypted SSH connections for  
multiple CLI-based sessions over the network are available (session 0  
to session 4). After the execution shell starts, the CLI-based session  
time-out value returns to the default of 10 minutes.  
•
Specify the number of times that a client can re-authenticate to the  
server. The default is 3; the range is 0 to 5.  
Repeat this step when configuring both parameters.  
Return to privileged EXEC mode.  
Step 4  
Step 5  
end  
show ip ssh  
Display the version and configuration information for your SSH server.  
or  
show ssh  
Display the status of the SSH server connections on the switch.  
(Optional) Save your entries in the configuration file.  
Step 6  
copy running-config startup-config  
To return to the default SSH control parameters, use the no ip ssh {timeout | authentication-retries}  
global configuration command.  
Displaying the SSH Configuration and Status  
To display the SSH server configuration and status, use one or more of the privileged EXEC commands  
in Table 5-2:  
Table 5-2  
Commands for Displaying the SSH Server Configuration and Status  
Command  
show ip ssh  
show ssh  
Purpose  
Shows the version and configuration information for the SSH server.  
Shows the status of the SSH server.  
For more information about these commands, see the “Secure Shell Commands” section in the “Other  
Security Features” chapter of the Cisco IOS Security Command Reference, Cisco IOS Release 12.2, at  
this URL:  
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fsecur_r/fothercr/  
srfssh.htm.  
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C H A P T E R  
6
Configuring IEEE 802.1x Port-Based  
Authentication  
This chapter describes how to configure IEEE 802.1x port-based authentication on the Cisco Systems  
Intelligent Gigabit Ethernet Switch Module to prevent unauthorized devices (clients) from gaining  
access to the network.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release and the “RADIUS Commands” section in the .  
This chapter consists of these sections:  
•
•
•
Understanding IEEE 802.1x Port-Based Authentication, page 6-1  
Configuring IEEE 802.1x Authentication, page 6-11  
Displaying IEEE 802.1x Statistics and Status, page 6-25  
Understanding IEEE 802.1x Port-Based Authentication  
The IEEE 802.1x standard defines a client-server-based access control and authentication protocol that  
prevents unauthorized clients from connecting to a LAN through publicly accessible ports unless they  
are properly authenticated. The authentication server authenticates each client connected to a switch port  
before making available any services offered by the switch or the LAN.  
Until the client is authenticated, IEEE 802.1x access control allows only Extensible Authentication  
Protocol over LAN (EAPOL), Cisco Discovery Protocol (CDP), and Spanning Tree Protocol (STP)  
traffic through the port to which the client is connected. After authentication is successful, normal traffic  
can pass through the port.  
These sections describe IEEE 802.1x port-based authentication:  
•
•
•
•
•
•
Device Roles, page 6-2  
Authentication Initiation and Message Exchange, page 6-3  
Ports in Authorized and Unauthorized States, page 6-4  
IEEE 802.1x Accounting, page 6-5  
IEEE 802.1x Accounting Attribute-Value Pairs, page 6-5  
IEEE 802.1x Host Mode, page 6-6  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Understanding IEEE 802.1x Port-Based Authentication  
•
•
•
•
•
Using IEEE 802.1x with Port Security, page 6-7  
Using IEEE 802.1x with Voice VLAN Ports, page 6-8  
Using IEEE 802.1x with VLAN Assignment, page 6-8  
Using IEEE 802.1x with Guest VLAN, page 6-9  
Using IEEE 802.1x with Wake-on-LAN, page 6-10  
Device Roles  
With IEEE 802.1x port-based authentication, the devices in the network have specific roles as shown in  
Figure 6-1.  
Figure 6-1  
IEEE 802.1x Device Roles  
Authentication  
server  
(RADIUS)  
Catalyst 2950,  
2955, or 3550  
(switch)  
BladeCenter  
BladeCenter  
•
Client—the device (workstation) that requests access to the LAN and switch services and responds  
to requests from the switch.The workstation must be running IEEE 802.1x-compliant client software  
such as that offered in the Microsoft Windows XP operating system. (The client is the supplicant in  
the IEEE 802.1x specification.)  
Note  
To resolve Windows XP network connectivity and IEEE 802.1x authentication issues, read  
the Microsoft Knowledge Base article at this URL:  
http://support.microsoft.com/support/kb/articles/Q303/5/97.ASP  
•
Authentication server—performs the actual authentication of the client. The authentication server  
validates the identity of the client and notifies the switch whether or not the client is authorized to  
access the LAN and switch services. Because the switch acts as the proxy, the authentication service  
is transparent to the client. In this release, the RADIUS security system with Extensible  
Authentication Protocol (EAP) extensions is the only supported authentication server. It is available  
in Cisco Secure Access Control Server Version 3.0 or later. RADIUS operates in a client/server  
model in which secure authentication information is exchanged between the RADIUS server and  
one or more RADIUS clients.  
•
Switch (edge switch or wireless access point)—controls the physical access to the network based on  
the authentication status of the client. The switch acts as an intermediary (proxy) between the client  
and the authentication server, requesting identity information from the client, verifying that  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Understanding IEEE 802.1x Port-Based Authentication  
information with the authentication server, and relaying a response to the client. The switch includes  
the RADIUS client, which is responsible for encapsulating and decapsulating the EAP frames and  
interacting with the authentication server.  
When the switch receives EAPOL frames and relays them to the authentication server, the Ethernet  
header is stripped, and the remaining EAP frame is re-encapsulated in the RADIUS format. The  
EAP frames are not modified during encapsulation, and the authentication server must support EAP  
within the native frame format. When the switch receives frames from the authentication server, the  
server frame header is removed, leaving the EAP frame, which is then encapsulated for Ethernet and  
sent to the client.  
The devices that can act as intermediaries include the Cisco Systems Intelligent Gigabit Ethernet Switch  
Modules, Catalyst 3750, 3560, 3550, 2970, 2955, 2950, 2940 switches, or a wireless access point. These  
devices must be running software that supports the RADIUS client and IEEE 802.1x.  
Authentication Initiation and Message Exchange  
The switch or the client can initiate authentication. If you enable authentication on a port by using the  
dot1x port-control auto interface configuration command, the switch initiates authentication when the  
link state changes from down to up or periodically as long as the port remains up and unauthenticated.  
The switch sends an EAP-request/identity frame to the client to request its identity. Upon receipt of the  
frame, the client responds with an EAP-response/identity frame.  
However, if during bootup, the client does not receive an EAP-request/identity frame from the switch,  
the client can initiate authentication by sending an EAPOL-start frame, which prompts the switch to  
request the client identity.  
Note  
If IEEE 802.1x is not enabled or supported on the network access device, any EAPOL frames from the  
client are dropped. If the client does not receive an EAP-request/identity frame after three attempts to  
start authentication, the client sends frames as if the port is in the authorized state. A port in the  
authorized state effectively means that the client has been successfully authenticated. For more  
information, see the “Ports in Authorized and Unauthorized States” section on page 6-4.  
When the client supplies its identity, the switch begins its role as the intermediary, passing EAP frames  
between the client and the authentication server until authentication succeeds or fails. If the  
authentication succeeds, the switch port becomes authorized. For more information, see the “Ports in  
Authorized and Unauthorized States” section on page 6-4.  
The specific exchange of EAP frames depends on the authentication method being used. Figure 6-2  
shows a message exchange initiated by the client using the One-Time-Password (OTP) authentication  
method with a RADIUS server.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Understanding IEEE 802.1x Port-Based Authentication  
Figure 6-2  
Message Exchange  
Authentication  
server  
(RADIUS)  
Blade  
Center  
IGESM  
EAPOL-Start  
EAP-Request/Identity  
EAP-Response/Identity  
EAP-Request/OTP  
EAP-Response/OTP  
EAP-Success  
RADIUS Access-Request  
RADIUS Access-Challenge  
RADIUS Access-Request  
RADIUS Access-Accept  
Port Authorized  
EAPOL-Logoff  
Port Unauthorized  
Ports in Authorized and Unauthorized States  
Depending on the switch port state, the switch can grant a client access to the network. The port starts  
in the unauthorized state. While in this state, the port that is not configured as a voice VLAN port  
disallows all ingress and egress traffic except for IEEE 802.1x, CDP, and STP packets. When a client is  
successfully authenticated, the port changes to the authorized state, allowing all traffic for the client to  
flow normally. If the port is configured as a voice VLAN port, the port allows VoIP traffic and IEEE  
802.1x protocol packets before the client is successfully authenticated.  
If a client that does not support IEEE 802.1x connects to an unauthorized IEEE 802.1x port, the switch  
requests the client’s identity. In this situation, the client does not respond to the request, the port remains  
in the unauthorized state, and the client is not granted access to the network.  
In contrast, when an IEEE 802.1x-enabled client connects to a port that is not running the IEEE 802.1x  
standard, the client initiates the authentication process by sending the EAPOL-start frame. When no  
response is received, the client sends the request for a fixed number of times. Because no response is  
received, the client begins sending frames as if the port is in the authorized state.  
You control the port authorization state by using the dot1x port-control interface configuration  
command and these keywords:  
•
force-authorized—disables IEEE 802.1x authentication and causes the port to transition to the  
authorized state without any authentication exchange required. The port sends and receives normal  
traffic without IEEE 802.1x-based authentication of the client. This is the default setting.  
•
force-unauthorized—causes the port to remain in the unauthorized state, ignoring all attempts by  
the client to authenticate. The switch cannot provide authentication services to the client through the  
interface.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Understanding IEEE 802.1x Port-Based Authentication  
•
auto—enables IEEE 802.1x authentication and causes the port to begin in the unauthorized state,  
allowing only EAPOL frames to be sent and received through the port. The authentication process  
begins when the link state of the port transitions from down to up or when an EAPOL-start frame is  
received. The switch requests the identity of the client and begins relaying authentication messages  
between the client and the authentication server. Each client attempting to access the network is  
uniquely identified by the switch by using the client’s MAC address.  
If the client is successfully authenticated (receives an Accept frame from the authentication server), the  
port state changes to authorized, and all frames from the authenticated client are allowed through the  
port. If the authentication fails, the port remains in the unauthorized state, but authentication can be  
retried. If the authentication server cannot be reached, the switch can resend the request. If no response  
is received from the server after the specified number of attempts, authentication fails, and network  
access is not granted.  
When a client logs off, it sends an EAPOL-logoff message, causing the switch port to transition to the  
unauthorized state.  
If the link state of a port transitions from up to down, or if an EAPOL-logoff frame is received, the port  
returns to the unauthorized state.  
IEEE 802.1x Accounting  
The IEEE 802.1x standard defines how users are authorized and authenticated for network access but  
does not keep track of network usage. IEEE 802.1x accounting is disabled by default. You can enable  
IEEE 802.1x accounting to monitor this activity on IEEE 802.1x-enabled ports:  
•
•
•
•
•
User successfully authenticates.  
User logs off.  
Link-down occurs.  
Re-authentication successfully occurs.  
Re-authentication fails.  
The switch does not log IEEE 802.1x accounting information. Instead, it sends this information to the  
RADIUS server, which must be configured to log accounting messages.  
IEEE 802.1x Accounting Attribute-Value Pairs  
The information sent to the RADIUS server is represented in the form of Attribute-Value (AV) pairs.  
These AV pairs provide data for different applications. (For example, a billing application might require  
information that is in the Acct-Input-Octets or the Acct-Output-Octets attributes of a RADIUS packet.)  
AV pairs are automatically sent by a switch that is configured for IEEE 802.1x accounting. Three types  
of RADIUS accounting packets are sent by a switch:  
•
•
•
START–sent when a new user session starts  
INTERIM–sent during an existing session for updates  
STOP–sent when a session terminates  
Table 6-1 lists the AV pairs and when they are sent are sent by the switch:  
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Understanding IEEE 802.1x Port-Based Authentication  
Table 6-1  
Accounting AV Pairs  
Attribute Number AV Pair Name  
START  
Always  
Always  
Always  
Never  
INTERIM  
Always  
Always  
Always  
STOP  
Attribute[1]  
Attribute[4]  
Attribute[5]  
Attribute[8]  
Attribute[25]  
Attribute[30]  
Attribute[31]  
Attribute[40]  
Attribute[41]  
Attribute[42]  
Attribute[43]  
Attribute[44]  
Attribute[45]  
Attribute[46]  
Attribute[49]  
Attribute[61]  
User-Name  
Always  
Always  
Always  
NAS-IP-Address  
NAS-Port  
Framed-IP-Address  
Class  
Sometimes1 Sometimes1  
Always  
Always  
Always  
Always  
Always  
Never  
Always  
Always  
Always  
Always  
Always  
Never  
Always  
Always  
Always  
Always  
Always  
Always  
Always  
Always  
Always  
Always  
Always  
Always  
Called-Station-ID  
Calling-Station-ID  
Acct-Status-Type  
Acct-Delay-Time  
Acct-Input-Octets  
Acct-Output-Octets  
Acct-Session-ID  
Acct-Authentic  
Acct-Session-Time  
Acct-Terminate-Cause  
NAS-Port-Type  
Never  
Never  
Always  
Always  
Never  
Always  
Always  
Never  
Never  
Never  
Always  
Always  
1. The Framed-IP-Address AV pair is sent only if a valid Dynamic Host Control Protocol (DHCP) binding  
exists for the host in the DHCP snooping bindings table.  
For more information about AV pairs, see RFC 3580, “IEEE 802.1X Remote Authentication Dial In User  
Service (RADIUS) Usage Guidelines.”  
IEEE 802.1x Host Mode  
You can configure an IEEE 802.1x port for single-host or for multiple-hosts mode. In single-host mode  
(see Figure 6-1 on page 6-2), only one client can be connected to the IEEE 802.1x-enabled switch port.  
The switch detects the client by sending an EAPOL frame when the port link state changes to the up  
state. If a client leaves or is replaced with another client, the switch changes the port link state to down,  
and the port returns to the unauthorized state.  
In multiple-hosts mode, you can attach multiple hosts to a single IEEE 802.1x-enabled port. Figure 6-3  
on page 6-7 shows IEEE 802.1x port-based authentication in a wireless LAN. In this mode, only one of  
the attached clients must be authorized for all clients to be granted network access. If the port becomes  
unauthorized (re-authentication fails or an EAPOL-logoff message is received), the switch denies  
network access to all of the attached clients. In this topology, the wireless access point is responsible for  
authenticating the clients attached to it, and it also acts as a client to the switch.  
With the multiple-hosts mode enabled, you can use IEEE 802.1x to authenticate the port and port  
security to manage network access for all MAC addresses, including that of the client.  
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Understanding IEEE 802.1x Port-Based Authentication  
Figure 6-3  
Multiple Host Mode Example  
Authentication  
Access point  
server  
(RADIUS)  
Wireless clients  
Using IEEE 802.1x with Port Security  
You can configure an IEEE 802.1x port with port security in either single-host or multiple-hosts mode.  
(You must also configure port security on the port by using the switchport port-security interface  
configuration command.) When you enable port security and IEEE 802.1x on a port, IEEE 802.1x  
authenticates the port, and port security manages network access for all MAC addresses, including that  
of the client. You can then limit the number or group of clients that can access the network through an  
IEEE 802.1x port.  
These are some examples of the interaction between IEEE 802.1x and port security on the switch:  
•
When a client is authenticated, and the port security table is not full, the client’s MAC address is  
added to the port security list of secure hosts. The port then proceeds to come up normally.  
When a client is authenticated and manually configured for port security, it is guaranteed an entry  
in the secure host table (unless port security static aging has been enabled).  
A security violation occurs if the client is authenticated, but port security table is full. This can  
happen if the maximum number of secure hosts has been statically configured, or if the client ages  
out of the secure host table. If the client’s address is aged out, its place in the secure host table can  
be taken by another host.  
The port security violation modes determine the action for security violations. For more  
information, see the “Security Violations” section on page 15-5.  
•
When an IEEE 802.1x client logs off, the port transitions back to an unauthenticated state, and all  
dynamic entries in the secure host table are cleared, including the entry for the client. Normal  
authentication then takes place.  
•
•
If the port is administratively shut down, the port becomes unauthenticated, and all dynamic entries  
are removed from the secure host table.  
Port security and a voice VLAN can be configured simultaneously on an IEEE 802.1x port that is  
in either single-host or multiple-hosts mode. Port security applies to both the voice VLAN identifier  
(VVID) and the port VLAN identifier (PVID).  
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Understanding IEEE 802.1x Port-Based Authentication  
•
When an IEEE 802.1x client address is manually removed from the port security table, we  
recommend that you re-authenticate the client by entering the dot1x re-authenticate privileged  
EXEC command.  
For more information about enabling port security on your switch, see the “Configuring Port Security”  
section on page 15-4.  
Using IEEE 802.1x with Voice VLAN Ports  
A voice VLAN port is a special access port associated with two VLAN identifiers:  
•
•
VVID to carry voice traffic to and from the IP phone. The VVID is used to configure the IP phone  
connected to the port.  
PVID to carry the data traffic to and from the workstation connected to the switch through the IP  
phone. The PVID is the native VLAN of the port.  
In single-host mode, only the IP phone is allowed on the voice VLAN. In multiple-hosts mode,  
additional clients can send traffic on the voice VLAN after a supplicant is authenticated on the PVID.  
When multiple-hosts mode is enabled, the supplicant authentication affects both the PVID and the  
VVID.  
A voice VLAN port becomes active when there is a link, and the device MAC address appears after the  
first CDP message from the IP phone. Cisco IP phones do not relay CDP messages from other devices.  
As a result, if several Cisco IP phones are connected in series, the switch recognizes only the one directly  
connected to it. When IEEE 802.1x is enabled on a voice VLAN port, the switch drops packets from  
unrecognized Cisco IP phones more than one hop away.  
When IEEE 802.1x is enabled on a port, you cannot configure a port VLAN that is equal to a voice  
VLAN.  
Using IEEE 802.1x with VLAN Assignment  
You can limit network access for certain users by using VLAN assignment. After successful IEEE  
802.1x authentication of a port, the RADIUS server sends the VLAN assignment to configure the switch  
port. The RADIUS server database maintains the username-to-VLAN mappings, which assigns the  
VLAN based on the username of the client connected to the switch port.  
When configured on the switch and the RADIUS server, IEEE 802.1x with VLAN assignment has these  
characteristics:  
•
If no VLAN is supplied by the RADIUS server or if IEEE 802.1x authorization is disabled, the port  
is configured in its access VLAN after successful authentication.  
•
If IEEE 802.1x authorization is enabled but the VLAN information from the RADIUS server is not  
valid, the port returns to the unauthorized state and remains in the configured access VLAN. This  
prevents ports from appearing unexpectedly in an inappropriate VLAN because of a configuration  
error.  
Configuration errors could include specifying a malformed VLAN ID, a nonexistent VLAN ID, or  
attempted assignment to a voice VLAN ID.  
•
•
If IEEE 802.1x authorization is enabled and all information from the RADIUS server is valid, the  
port is placed in the specified VLAN after authentication.  
If the multiple-hosts mode is enabled on an IEEE 802.1x port, all hosts are placed in the same VLAN  
(specified by the RADIUS server) as the first authenticated host.  
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Understanding IEEE 802.1x Port-Based Authentication  
•
•
If IEEE 802.1x and port security are enabled on a port, the port is placed in the RADIUS-server  
assigned VLAN.  
If IEEE 802.1x is disabled on the port, it is returned to the configured access VLAN.  
When the port is in the force authorized, force unauthorized, unauthorized, or shutdown state, it is placed  
in the configured access VLAN.  
If an IEEE 802.1x port is authenticated and put in the RADIUS-server assigned VLAN, any change to  
the port access VLAN configuration does not take effect.  
The IEEE 802.1x with VLAN assignment feature is not supported on trunk ports, dynamic ports, or with  
dynamic-access port assignment through a VLAN Membership Policy Server (VMPS).  
To configure VLAN assignment you need to perform these tasks:  
•
•
Enable AAA authorization.  
Enable IEEE 802.1x (the VLAN assignment feature is automatically enabled when you configure  
IEEE 802.1x on an access port).  
•
Assign vendor-specific tunnel attributes in the RADIUS server. The RADIUS server must return  
these attributes to the switch:  
–
–
–
[64] Tunnel-Type = VLAN  
[65] Tunnel-Medium-Type = IEEE 802  
[81] Tunnel-Private-Group-ID = VLAN name or VLAN ID  
Attribute [64] must contain the value VLAN (type 13). Attribute [65] must contain the value IEEE  
802 (type 6). Attribute [81] specifies the VLAN name or VLAN ID assigned to the IEEE  
802.1x-authenticated user.  
For examples of tunnel attributes, see the “Configuring the Switch to Use Vendor-Specific RADIUS  
Attributes” section on page 5-28.  
Using IEEE 802.1x with Guest VLAN  
You can configure a guest VLAN for each IEEE 802.1x port on the switch to provide limited services  
to clients, such as downloading the IEEE 802.1x client. These clients might be upgrading their system  
for IEEE 802.1x authentication, and some hosts, such as Windows 98 systems, might not be IEEE  
802.1x-capable.  
When you enable a guest VLAN on an IEEE 802.1x port, the switch assigns clients to a guest VLAN  
when the switch does not receive a response to its EAP request/identity frame or when EAPOL packets  
are not sent by the client.  
Before Cisco IOS Release 12.1(22)AY, the switch did not maintain the EAPOL packet history and  
allowed clients that failed authentication access to the guest VLAN, regardless of whether EAPOL  
packets had been detected on the interface. You can enable this optional behavior by using the dot1x  
guest-vlan supplicant global configuration command.  
With Cisco IOS Release 12.1(22)AY and later, the switch maintains the EAPOL packet history. If an  
EAPOL packet is detected on the interface during the lifetime of the link, the switch determines that the  
device connected to that interface is an 802.1x-capable supplicant, and the interface does not transition  
to the guest VLAN state. EAPOL history is cleared if the interface link status goes down. If no EAPOL  
packet is detected on the interface, it is transitioned to the guest VLAN state.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Understanding IEEE 802.1x Port-Based Authentication  
Note  
If an EAPOL packet is detected on the wire after the interface has transitioned to the guest VLAN, the  
interface reverts to an unauthorized state, and 802.1x authentication restarts.  
Any number of IEEE 802.1x-incapable clients are allowed access when the switch port is moved to the  
guest VLAN. If an IEEE 802.1x-capable client joins the same port on which the guest VLAN is  
configured, the port is put into the unauthorized state in the user-configured access VLAN, and  
authentication is restarted.  
Guest VLANs are supported on IEEE 802.1x ports in single-host or multiple-hosts mode.  
You can configure any active VLAN except an RSPAN VLAN or a voice VLAN as an IEEE 802.1x  
guest VLAN. The guest VLAN feature is not supported on trunk ports; it is supported only on access  
ports.  
For configuration steps, see the “Configuring a Guest VLAN” section on page 6-20.  
Using IEEE 802.1x with Wake-on-LAN  
The IEEE 802.1x wake-on-LAN (WoL) feature allows dormant PCs to be powered when the switch  
receives a specific Ethernet frame, known as the magic packet. You can use this feature in environments  
where administrators need to connect to systems that have been powered down.  
When hosts that use WoL are attached through IEEE 802.1x ports and the host powers down, the IEEE  
802.1x port becomes unauthorized. In this state, the port can only receive and send EAPOL packets, and  
WoL magic packets cannot reach the host. When the PC is powered down, it is not authenticated, and  
the switch port is not opened.  
When the switch uses IEEE 802.1x with WoL, the switch sends packets to unauthorized IEEE 802.1x  
ports. This feature is also known as the Unidirectional Controlled Port in the IEEE 802.1x specification.  
Note  
If PortFast is not enabled on the port, the port is forced to the bidirectional state.  
Unidirectional State  
When you configure a port as unidirectional by using the dot1x control-direction in interface  
configuration command, the port changes to the spanning-tree forwarding state.  
When WoL is enabled, the connected host is in the sleeping mode or power-down state. The host does  
not exchange traffic with other devices in the network. If the host connected to the unidirectional port  
that cannot send traffic to the network, the host can only receive traffic from other devices in the  
network. If the unidirectional port receives incoming traffic, the port returns to the default bidirectional  
state, and the port changes to the spanning-tree blocking state. When the port changes to the initialize  
state, no traffic other than EAPOL packet is allowed. When the port returns to the bidirectional state, the  
switch starts a 5-minute timer. If the port is not authenticated before the timer expires, the port becomes  
a unidirectional port.  
Bidirectional State  
When you configure a port as bidirectional by using the dot1x control-direction both interface config-  
uration command, the port is access-controlled in both directions. In this state, the switch port does not  
receive or send packets.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Configuring IEEE 802.1x Authentication  
These sections describe how to configure IEEE 802.1x port-based authentication on your switch:  
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Default IEEE 802.1x Configuration, page 6-11  
IEEE 802.1x Configuration Guidelines, page 6-12  
Enabling IEEE 802.1x Authentication, page 6-13 (required)  
Configuring the Switch-to-RADIUS-Server Communication, page 6-14 (required)  
Enabling Periodic Re-Authentication, page 6-16 (optional)  
Manually Re-Authenticating a Client Connected to a Port, page 6-17 (optional)  
Changing the Quiet Period, page 6-17 (optional)  
Changing the Switch-to-Client Retransmission Time, page 6-18 (optional)  
Setting the Switch-to-Client Frame-Retransmission Number, page 6-19 (optional)  
Configuring the Host Mode, page 6-20 (optional)  
Configuring a Guest VLAN, page 6-20 (optional)  
Resetting the IEEE 802.1x Configuration to the Default Values, page 6-22 (optional)  
Configuring IEEE 802.1x Authentication, page 6-22 (optional)  
Configuring IEEE 802.1x Accounting, page 6-24 (optional)  
Default IEEE 802.1x Configuration  
Table 6-2 shows the default IEEE 802.1x configuration.  
Table 6-2  
Default IEEE 802.1x Configuration  
Feature  
Default Setting  
Disabled.  
AAA  
RADIUS server  
•
•
•
IP address  
•
•
•
None specified.  
UDP authentication port  
Key  
1812.  
None specified.  
Switch IEEE 802.1x enable state  
Disabled.  
Per-interface IEEE 802.1x enable state  
Disabled (force-authorized).  
The port sends and receives normal traffic without IEEE  
802.1x-based authentication of the client.  
Periodic re-authentication  
Disabled.  
Number of seconds between  
re-authentication attempts  
3600 seconds.  
Quiet period  
60 seconds (number of seconds that the switch remains in  
the quiet state following a failed authentication exchange  
with the client).  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Table 6-2  
Default IEEE 802.1x Configuration (continued)  
Feature  
Default Setting  
Retransmission time  
30 seconds (number of seconds that the switch should  
wait for a response to an EAP request/identity frame  
from the client before resending the request).  
Maximum retransmission number  
2 times (number of times that the switch will send an  
EAP-request/identity frame before restarting the  
authentication process).  
Host mode  
Single-host mode.  
None specified.  
Guest VLAN  
Client timeout period  
30 seconds (when relaying a request from the  
authentication server to the client, the amount of time the  
switch waits for a response before resending the request  
to the client.  
Authentication server timeout period  
30 seconds (when relaying a response from the client to  
the authentication server, the amount of time the switch  
waits for a reply before resending the response to the  
server. This setting is not configurable.)  
IEEE 802.1x Configuration Guidelines  
These are the IEEE 802.1x authentication configuration guidelines:  
•
•
When IEEE 802.1x is enabled, ports are authenticated before any other Layer 2 features are enabled.  
The IEEE 802.1x protocol is supported on Layer 2 static-access ports and voice VLAN ports, but it  
is not supported on these port types:  
–
Trunk port—If you try to enable IEEE 802.1x on a trunk port, an error message appears, and  
IEEE 802.1x is not enabled. If you try to change the mode of an IEEE 802.1x-enabled port to  
trunk, the port mode is not changed.  
–
Dynamic ports—A port in dynamic mode can negotiate with its neighbor to become a trunk  
port. If you try to enable IEEE 802.1x on a dynamic port, an error message appears, and IEEE  
802.1x is not enabled. If you try to change the mode of an IEEE 802.1x-enabled port to dynamic,  
the port mode is not changed.  
–
Dynamic-access ports—If you try to enable IEEE 802.1x on a dynamic-access (VLAN Query  
Protocol [VQP]) port, an error message appears, and IEEE 802.1x is not enabled. If you try to  
change an IEEE 802.1x-enabled port to dynamic VLAN assignment, an error message appears,  
and the VLAN configuration is not changed.  
–
–
EtherChannel ports—Do not configure a port that is an active or a not-yet-active member of an  
EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel  
port, an error message appears, and IEEE 802.1x is not enabled.  
IEEE Switched Port Analyzer (SPAN) and Remote SPAN (RSPAN) destination ports—You  
cannot enable IEEE 802.1x on a port that is a SPAN or RSPAN destination port or that is an  
RSPAN reflector port. However, you can enable IEEE 802.1x on a SPAN or RSPAN source  
port.  
•
You can configure any VLAN, except an RSPAN VLAN or a voice VLAN, as an IEEE 802.1x guest  
VLAN. The guest VLAN feature is not supported on trunk ports; it is supported only on access ports.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
•
•
•
When IEEE 802.1x is enabled on a port, you cannot configure a port VLAN that is equal to a voice  
VLAN.  
The IEEE 802.1x with VLAN assignment feature is not supported on trunk ports, dynamic ports, or  
with dynamic-access port assignment through a VMPS.  
Before globally enabling IEEE 802.1x on a switch by entering the dot1x system-auth-control  
global configuration command, remove the EtherChannel configuration from the interfaces on  
which IEEE 802.1x and EtherChannel are configured.  
•
If you are using a device running the Cisco Access Control Server (ACS) application for IEEE  
802.1x authentication with EAP-Transparent LAN Services (TLS) and EAP-MD5 and your switch  
is running Cisco IOS Release 12.1(14)EA1, make sure that the device is running ACS Version 3.2.1  
or later.  
Enabling IEEE 802.1x Authentication  
To enable IEEE 802.1x port-based authentication, you must enable authentication, authorization, and  
accounting (AAA) and specify the authentication method list. A method list describes the sequence and  
authentication method to be queried to authenticate a user.  
To allow VLAN assignment, you must enable AAA authorization to configure the switch for all  
network-related service requests.  
Beginning in privileged EXEC mode, follow these steps to configure IEEE 802.1x port-based  
authentication. This procedure is required.  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
aaa new-model  
Enter global configuration mode.  
Enable AAA.  
aaa authentication dot1x {default}  
Create an IEEE 802.1x authentication method list.  
method1  
To create a default list that is used when a named list is not specified in  
the authentication command, use the default keyword followed by the  
method that is to be used in default situations. The default method list is  
automatically applied to all ports.  
For method1, enter the group radius keyword to use the list of all  
RADIUS servers for authentication.  
Note  
Though other keywords are visible in the command-line help  
string, only the default and group radius keywords are  
supported.  
Step 4  
Step 5  
dot1x system-auth-control  
Enable IEEE 802.1x authentication globally on the switch.  
aaa authorization network {default} (Optional) Configure the switch for user RADIUS authorization for all  
group radius  
network-related service requests, such as VLAN assignment.  
Step 6  
Step 7  
radius-server host ip-address  
radius-server key string  
(Optional) Specify the IP address of the RADIUS server.  
(Optional) Specify the authentication and encryption key used between  
the switch and the RADIUS daemon running on the RADIUS server.  
Step 8  
interface interface-id  
Specify the port connected to the client that is to be enabled for IEEE  
802.1x authentication, and enter interface configuration mode.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Command  
Purpose  
Step 9  
swtichport mode access  
(Optional) Set the port to access mode only if you configured the RADIUS  
server in Step 6 and Step 7.  
Step 10  
dot1x port-control auto  
Enable IEEE 802.1x authentication on the interface.  
For feature interaction information, see the “IEEE 802.1x Configuration  
Guidelines” section on page 6-12.  
Step 11  
Step 12  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show dot1x  
Check the Status column in the IEEE 802.1x Port Summary section of the  
display. An enabled status means the port-control value is set either to  
auto or to force-unauthorized.  
Step 13  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable AAA, use the no aaa new-model global configuration command. To disable IEEE 802.1x  
AAA authentication, use the no aaa authentication dot1x {default | list-name} global configuration  
command. To disable IEEE 802.1x AAA authorization, use the no aaa authorization global  
configuration command. To disable IEEE 802.1x authentication on the switch, use the no dot1x  
system-auth-control global configuration command.  
This example shows how to enable AAA and IEEE 802.1x on a port:  
Switch# configure terminal  
Switch(config)# aaa new-model  
Switch(config)# aaa authentication dot1x default group radius  
Switch(config)# dot1x system-auth-control  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# switchport mode access  
Switch(config-if)# dot1x port-control auto  
Switch(config-if)# end  
Configuring the Switch-to-RADIUS-Server Communication  
RADIUS security servers are identified by their host name or IP address, host name and specific UDP  
port numbers, or IP address and specific UDP port numbers. The combination of the IP address and UDP  
port number creates a unique identifier, which enables RADIUS requests to be sent to multiple UDP  
ports on a server at the same IP address. If two different host entries on the same RADIUS server are  
configured for the same service—for example, authentication—the second host entry configured acts as  
the fail-over backup to the first one. The RADIUS host entries are tried in the order that they were  
configured.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Beginning in privileged EXEC mode, follow these steps to configure the RADIUS server parameters on  
the switch. This procedure is required.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
radius-server host {hostname |  
ip-address} auth-port port-number key  
string  
Configure the RADIUS server parameters on the switch.  
For hostname | ip-address, specify the host name or IP address of the  
remote RADIUS server.  
For auth-port port-number, specify the UDP destination port for  
authentication requests. The default is 1812.  
For key string, specify the authentication and encryption key used  
between the switch and the RADIUS daemon running on the RADIUS  
server. The key is a text string that must match the encryption key used on  
the RADIUS server.  
Note  
Always configure the key as the last item in the radius-server  
host command syntax because leading spaces are ignored, but  
spaces within and at the end of the key are used. If you use spaces  
in the key, do not enclose the key in quotation marks unless the  
quotation marks are part of the key. This key must match the  
encryption used on the RADIUS daemon.  
If you want to use multiple RADIUS servers, re-enter this command.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
Step 5  
end  
show running-config  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To delete the specified RADIUS server, use the no radius-server host {hostname | ip-address} global  
configuration command.  
This example shows how to specify the server with IP address 172.20.39.46 as the RADIUS server, to  
use port 1612 as the authorization port, and to set the encryption key to rad123, matching the key on the  
RADIUS server:  
Switch(config)# radius-server host 172.l20.39.46 auth-port 1612 key rad123  
You can globally configure the timeout, retransmission, and encryption key values for all RADIUS  
servers by using the radius-server host global configuration command. If you want to configure these  
options on a per-server basis, use the radius-server timeout, radius-server retransmit, and the  
radius-server key global configuration commands. For more information, see the “Configuring Settings  
for All RADIUS Servers” section on page 5-28.  
You also need to configure some settings on the RADIUS server. These settings include the IP address  
of the switch and the key string to be shared by both the server and the switch. For more information,  
see the RADIUS server documentation.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Configuring IEEE 802.1x Authentication Using a RADIUS Server  
Beginning in privileged EXEC mode, follow these steps to configure IEEE 802.1x authentication with a  
RADIUS server. The procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
interface interface-id  
dot1x guest-vlan vlan-id  
Enter global configuration mode.  
Specify the port to be configured, and enter interface configuration mode.  
Specify an active VLAN as an IEEE 802.1x guest VLAN. The range is 1  
to 4094.  
You can configure any active VLAN except an RSPAN VLAN, or a voice  
VLAN as an IEEE 802.1x guest VLAN.  
Step 4  
Step 5  
dot1x reauthentication  
Enable periodic re-authentication of the client, which is disabled by  
default.  
dot1x timeout reauth-period {seconds | Set the number of seconds between re-authentication attempts.  
server}  
The keywords have these meanings:  
•
seconds—Sets the number of seconds from 1 to 65535; the default is  
3600 seconds.  
•
server—Sets the number of seconds as the value of the  
Session-Timeout RADIUS attribute (Attribute[27]).  
This command affects the behavior of the switch only if periodic  
re-authentication is enabled.  
Step 6  
Step 7  
Step 8  
end  
Return to privileged EXEC mode.  
show dot1x interface interface-id  
copy running-config startup-config  
Verify your IEEE 802.1x authentication configuration.  
(Optional) Save your entries in the configuration file.  
This example shows how to configure IEEE 802.1x using a RADIUS server:  
Switch# configure terminal  
Switch(config)# interface gigabitethernet0/1  
Switch(config-if)# dot1x reauthentication  
Switch(config-if)# dot1x timeout reauth-period server  
Enabling Periodic Re-Authentication  
You can enable periodic IEEE 802.1x client re-authentication and specify how often it occurs. If you do  
not specify a time period before enabling re-authentication, the number of seconds between  
re-authentication attempts is 3600.  
Beginning in privileged EXEC mode, follow these steps to enable periodic re-authentication of the client  
and to configure the number of seconds between re-authentication attempts. This procedure is optional.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Command  
Purpose  
Step 1  
configure terminal  
Enter global configuration mode.  
Step 2  
Step 3  
Step 4  
interface interface-id  
Specify the interface to be configured, and enter interface configuration  
mode.  
dot1x reauthentication  
Enable periodic re-authentication of the client, which is disabled by  
default.  
dot1x timeout reauth-period {seconds | The keywords have these meanings:  
server}  
•
seconds—Sets the number of seconds from 1 to 65535; the default is  
3600 seconds.  
•
server—Sets the number of seconds as the value of the  
Session-Timeout RADIUS attribute (Attribute[27]). You can use this  
keyword when the switch uses IEEE 802.1x authentication with a  
RADIUS server.  
This command affects the behavior of the switch only if periodic  
re-authentication is enabled.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show dot1x interface interface-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable periodic re-authentication, use the no dot1x reauthentication interface configuration  
command. To return to the default number of seconds between re-authentication attempts, use the no  
dot1x timeout reauth-period global configuration command.  
This example shows how to enable periodic re-authentication and set the number of seconds between  
re-authentication attempts to 4000:  
Switch(config-if)# dot1x reauthentication  
Switch(config-if)# dot1x timeout reauth-period 4000  
Manually Re-Authenticating a Client Connected to a Port  
You can manually re-authenticate the client connected to a specific port at any time by entering the  
dot1x re-authenticate interface interface-id privileged EXEC command. This step is optional. If you  
want to enable or disable periodic re-authentication, see the “Enabling Periodic Re-Authentication”  
section on page 6-16.  
This example shows how to manually re-authenticate the client connected to a port:  
Switch# dot1x re-authenticate interface gigabitethernet0/17  
Changing the Quiet Period  
When the switch cannot authenticate the client, the switch remains idle for a set period of time, and then  
tries again. The idle time is determined by the quiet-period value. A failed authentication of the client  
might occur because the client provided an invalid password. You can provide a faster response time to  
the user by entering a smaller number than the default.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Beginning in privileged EXEC mode, follow these steps to change the quiet period. This procedure is  
optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to be configured, and enter interface configuration  
mode.  
Step 3  
dot1x timeout quiet-period seconds  
Set the number of seconds that the switch remains in the quiet state  
following a failed authentication exchange with the client.  
The range is 1 to 65535 seconds; the default is 60.  
Return to privileged EXEC mode.  
Step 4  
Step 5  
Step 6  
end  
show dot1x interface interface-id  
copy running-config startup-config  
Verify your entries.  
(Optional) Save your entries in the configuration file.  
To return to the default quiet time, use the no dot1x timeout quiet-period interface configuration  
command.  
This example shows how to set the quiet time on the switch to 30 seconds:  
Switch(config-if)# dot1x timeout quiet-period 30  
Changing the Switch-to-Client Retransmission Time  
The client responds to the EAP-request/identity frame from the switch with an EAP-response/identity  
frame. If the switch does not receive this response, it waits a set period of time (known as the  
retransmission time) and then resends the frame.  
Note  
You should change the default value of this command only to adjust for unusual circumstances such as  
unreliable links or specific behavioral problems with certain clients and authentication servers.  
Beginning in privileged EXEC mode, follow these steps to change the amount of time that the switch  
waits for client notification. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to be configured, and enter interface configuration  
mode.  
Step 3  
dot1x timeout tx-period seconds  
Set the number of seconds that the switch waits for a response to an  
EAP-request/identity frame from the client before resending the request.  
The range is 15 to 65535 seconds; the default is 30.  
Return to privileged EXEC mode.  
Step 4  
Step 5  
Step 6  
end  
show dot1x interface interface-id  
copy running-config startup-config  
Verify your entries.  
(Optional) Save your entries in the configuration file.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
To return to the default retransmission time, use the no dot1x timeout tx-period interface configuration  
command.  
This example shows how to set 60 as the number of seconds that the switch waits for a response to an  
EAP-request/identity frame from the client before resending the request:  
Switch(config-if)# dot1x timeout tx-period 60  
Setting the Switch-to-Client Frame-Retransmission Number  
In addition to changing the switch-to-client retransmission time, you can change the number of times  
that the switch sends an EAP-request/identity frame (assuming no response is received) to the client  
before restarting the authentication process.  
Note  
You should change the default value of this command only to adjust for unusual circumstances such as  
unreliable links or specific behavioral problems with certain clients and authentication servers.  
Beginning in privileged EXEC mode, follow these steps to set the switch-to-client frame-retransmission  
number. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to be configured, and enter interface configuration  
mode.  
Step 3  
dot1x max-req count  
Set the number of times that the switch sends an EAP-request/identity  
frame to the client before restarting the authentication process. The range  
is 1 to 10; the default is 2.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show dot1x interface interface-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return to the default retransmission number, use the no dot1x max-req interface configuration  
command.  
This example shows how to set 5 as the number of times that the switch sends an EAP-request/identity  
request before restarting the authentication process:  
Switch(config-if)# dot1x max-req 5  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Configuring the Host Mode  
Beginning in privileged EXEC mode, follow these steps to allow multiple hosts (clients) on an IEEE  
802.1x-authorized port that has the dot1x port-control interface configuration command set to auto.  
This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to which multiple hosts are indirectly attached, and  
enter interface configuration mode.  
Step 3  
dot1x host-mode multi-host  
Allow multiple hosts (clients) on an IEEE 802.1x-authorized port.  
Make sure that the dot1x port-control interface configuration command  
set is set to auto for the specified interface.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show dot1x interface interface-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable multiple hosts on the port, use the no dot1x host-mode multi-host interface configuration  
command.  
This example shows how to enable a port to allow multiple hosts:  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# dot1x port-control auto  
Switch(config-if)# dot1x host-mode multi-host  
Configuring a Guest VLAN  
When you configure a guest VLAN, clients that are not IEEE 802.1x-capable are put into the guest  
VLAN when the server does not receive a response to its EAPOL request/identity frame. Clients that are  
IEEE 802.1x-capable but fail authentication are not granted access to the network. The switch supports  
guest VLANs in single-host or multiple-hosts mode.  
You can enable optional guest VLAN behavior by using the dot1x guest-vlan supplicant global  
configuration command. When enabled, the switch does not maintain the EAPOL packet history and  
allows clients that fail authentication to access the guest VLAN, regardless of whether EAPOL packets  
had been detected on the interface. Clients that fail authentication can access the guest VLAN.  
Note  
Depending on the switch configuration, this process can take from less than a minute to several minutes.  
Beginning in privileged EXEC mode, follow these steps to configure a guest VLAN. This procedure is  
optional.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Command  
Purpose  
Step 1  
configure terminal  
Enter global configuration mode.  
Step 2  
interface interface-id  
Specify the interface to be configured, and enter interface configuration  
mode. For the supported interface types, see the “IEEE 802.1x  
Configuration Guidelines” section on page 6-12.  
Step 3  
Step 4  
Step 5  
switchport mode access  
dot1x port-control auto  
dot1x guest-vlan vlan-id  
Set the port to access mode.  
Enable IEEE 802.1x authentication on the port.  
Specify an active VLAN as an IEEE 802.1x guest VLAN. The range is 1  
to 4094.  
You can configure any active VLAN except an RSPAN VLAN or a voice  
VLAN as an IEEE 802.1x guest VLAN.  
Step 6  
Step 7  
Step 8  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show dot1x interface interface-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable and remove the guest VLAN, use the no dot1x guest-vlan interface configuration command.  
The port returns to the unauthorized state.  
This example shows how to enable VLAN 9 as an IEEE 802.1x guest VLAN on a port:  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# dot1x guest-vlan 9  
You can enable optional guest VLAN behavior by using the dot1x guest-vlan supplicant global  
configuration command. When enabled, the switch does not maintain the EAPOL packet history and  
allows clients that fail authentication access to the guest VLAN, regardless of whether EAPOL packets  
had been detected on the interface.  
Beginning in privileged EXEC mode, follow these steps to enable the optional guest VLAN behavior  
and to configure a guest VLAN. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
Enter global configuration mode.  
dot1x guest-vlan supplicant  
interface interface-id  
Enable the optional guest VLAN behavior globally on the switch.  
Specify the port to be configured, and enter interface configuration mode.  
For the supported port types, see the “IEEE 802.1x Configuration  
Guidelines” section on page 6-12.  
Step 4  
Step 5  
Step 6  
switchport mode access  
dot1x port-control auto  
dot1x guest-vlan vlan-id  
Set the port to access mode.  
Enable IEEE 802.1x authentication on the port.  
Specify an active VLAN as an IEEE 802.1x guest VLAN. The range is 1  
to 4094.  
You can configure any active VLAN except an RSPAN VLAN or a voice  
VLAN as an IEEE 802.1x guest VLAN.  
Step 7  
end  
Return to privileged EXEC mode.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Command  
Purpose  
Step 8  
Step 9  
show dot1x interface interface-id  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable the optional guest VLAN behavior, use the no dot1x guest-vlan supplicant global  
configuration command. To remove the guest VLAN, use the no dot1x guest-vlan interface  
configuration command. If the port is currently authorized in the guest VLAN, the port returns to the  
unauthorized state.  
This example shows how enable the optional guest VLAN behavior and to specify VLAN 5 as an IEEE  
802.1x guest VLAN:  
Switch(config)# dot1x guest-vlan supplicant  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# dot1x guest-vlan 5  
Resetting the IEEE 802.1x Configuration to the Default Values  
Beginning in privileged EXEC mode, follow these steps to reset the IEEE 802.1x configuration to the  
default values.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
interface interface-id  
Enter global configuration mode.  
Specify the interface to be configured, and enter interface configuration  
mode.  
Step 3  
Step 4  
Step 5  
Step 6  
dot1x default  
Reset the configurable IEEE 802.1x parameters to the default values.  
Return to privileged EXEC mode.  
end  
show dot1x interface interface-id  
copy running-config startup-config  
Verify your entries.  
(Optional) Save your entries in the configuration file.  
Configuring IEEE 802.1x Authentication  
To configure IEEE 802.1x port-based authentication, you must enable AAA and specify the  
authentication method list. A method list describes the sequence and authentication methods to be  
queried to authenticate a user.  
The software uses the first method listed to authenticate users. If that method fails to respond, the  
software selects the next authentication method in the method list. This process continues until there is  
successful communication with a listed authentication method or until all defined methods are  
exhausted. If authentication fails at any point in this cycle, the authentication process stops, and no other  
authentication methods are attempted.  
To allow VLAN assignment, you must enable AAA authorization to configure the switch for all  
network-related service requests.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
This is the IEEE 802.1x authentication, authorization and accounting process:  
Step 1  
Step 2  
Step 3  
Step 4  
Step 5  
Step 6  
A user connects to a port on the switch.  
Authentication is performed.  
VLAN assignment is enabled, as appropriate, based on the RADIUS server configuration.  
The switch sends a start message to an accounting server.  
Re-authentication is performed, as necessary.  
The switch sends an interim accounting update to the accounting server that is based on the result of  
re-authentication.  
Step 7  
Step 8  
The user disconnects from the port.  
The switch sends a stop message to the accounting server.  
Beginning in privileged EXEC mode, follow these steps to configure IEEE 802.1x port-based  
authentication:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
aaa new-model  
Enter global configuration mode.  
Enable AAA.  
aaa authentication dot1x {default}  
method1 [method2...]  
Create an IEEE 802.1x authentication method list.  
To create a default list that is used when a named list is not specified in  
the authentication command, use the default keyword followed by the  
methods that are to be used in default situations. The default method list  
is automatically applied to all ports.  
Enter at least one of these keywords:  
•
•
group radius—Use the list of all RADIUS servers for authentication.  
none—Use no authentication. The client is automatically  
authenticated by the switch without using the information supplied by  
the client.  
Step 4  
Step 5  
dot1x system-auth-control  
Enable IEEE 802.1x authentication globally on the switch.  
aaa authorization network {default} (Optional) Configure the switch for user RADIUS authorization for all  
group radius  
network-related service requests, such as VLAN assignment.  
Note  
Step 6  
Step 7  
interface interface-id  
Specify the port connected to the client that is to be enabled for IEEE  
802.1x authentication, and enter interface configuration mode.  
dot1x port-control auto  
Enable IEEE 802.1x authentication on the port.  
For feature interaction information, see the “IEEE 802.1x Configuration  
Guidelines” section on page 6-12.  
Step 8  
Step 9  
Step 10  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show dot1x  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Configuring IEEE 802.1x Authentication  
Configuring IEEE 802.1x Accounting  
Enabling AAA system accounting with IEEE 802.1x accounting allows system reload events to be sent  
to the accounting RADIUS server for logging. The server can then infer that all active IEEE 802.1x  
sessions are closed.  
Because RADIUS uses the unreliable UDP transport protocol, accounting messages might be lost due to  
poor network conditions. If the switch does not receive the accounting response message from the  
RADIUS server after a configurable number of retransmissions of an accounting request, this system  
message appears:  
Accounting message %s for session %s failed to receive Accounting Response.  
When the stop message is not sent successfully, this message appears:  
00:09:55: %RADIUS-3-NOACCOUNTINGRESPONSE: Accounting message Start for session  
172.20.50.145 sam 11/06/03 07:01:16 11000002 failed to receive Accounting Response.  
Note  
You must configure the RADIUS server to perform accounting tasks, such as logging start, stop, and  
interim-update messages and time stamps. To turn on these functions, enable logging of  
“Update/Watchdog packets from this AAA client” in your RADIUS server Network Configuration tab.  
Next, enable “CVS RADIUS Accounting” in your RADIUS server System Configuration tab.  
Beginning in privileged EXEC mode, follow these steps to configure IEEE 802.1x accounting after AAA  
is enabled on your switch. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the port to be configured, and enter interface configuration mode.  
Enable IEEE 802.1x accounting using the list of all RADIUS servers.  
aaa accounting dot1x default  
start-stop group radius  
Step 4  
aaa accounting system default  
start-stop group radius  
(Optional) Enables system accounting (using the list of all RADIUS  
servers) and generates system accounting reload event messages when the  
switch reloads.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEc mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Saves your entries in the configuration file.  
Use the show radius statistics privileged EXEC command to display the number of RADIUS messages  
that do not receive the accounting response message.  
This example shows how to configure IEEE 802.1x accounting. The first command configures the  
RADIUS server, specifying 1813 as the UDP port for accounting:  
Switch(config)# radius-server host 172.120.39.46 auth-port 1812 acct-port 1813 key rad123  
Switch(config)# aaa accounting dot1x default start-stop group radius  
Switch(config)# aaa accounting system default start-stop group radius  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Displaying IEEE 802.1x Statistics and Status  
Displaying IEEE 802.1x Statistics and Status  
To display IEEE 802.1x statistics for all interfaces, use the show dot1x all statistics privileged EXEC  
command. To display IEEE 802.1x statistics for a specific interface, use the show dot1x statistics  
interface interface-id privileged EXEC command.  
To display the IEEE 802.1x administrative and operational status for the switch, use the show dot1x all  
privileged EXEC command. To display the IEEE 802.1x administrative and operational status for a  
specific interface, use the show dot1x interface interface-id privileged EXEC command.  
For detailed information about the fields in these displays, see the command reference for this release.  
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Chapter 6 Configuring IEEE 802.1x Port-Based Authentication  
Displaying IEEE 802.1x Statistics and Status  
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C H A P T E R  
7
Configuring Interface Characteristics  
This chapter describes the types of interfaces on a Cisco Systems Intelligent Gigabit Ethernet Switch  
Module and how to configure them. The chapter has these sections:  
•
•
•
•
Understanding Interface Types, page 7-1  
Using the Interface Command, page 7-4  
Configuring Ethernet Interfaces, page 7-9  
Monitoring and Maintaining the Interfaces, page 7-13  
Note  
For complete syntax and usage information for the commands used in this chapter, see the switch  
command reference for this release and the online Cisco IOS Interface Command Reference for Cisco  
IOS Release 12.1.  
Understanding Interface Types  
This section describes the different types of interfaces supported by the switch with references to  
chapters that contain more detailed information about configuring these interface types. The rest of the  
chapter describes configuration procedures for switch ports.  
Note  
The switch has 4 external ports and 16 internal ports. For more information, see the “Using the Interface  
Command” section on page 7-4 and the switch hardware installation guide.  
Switch ports are Layer 2-only interfaces associated with a physical port. They are used for managing the  
physical interface and associated Layer 2 protocols and do not handle routing or bridging. A switch port  
can be an access port or a trunk port.  
You can configure a port as an access port or trunk port or let the Dynamic Trunking Protocol (DTP)  
operate on a per-port basis to determine if a switch port should be an access port or a trunk port by  
negotiating with the port on the other end of the link.  
Configure switch ports by using the switchport interface configuration commands. For detailed  
information about configuring access port and trunk port characteristics, see Chapter 12, “Configuring  
VLANs.”  
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Chapter 7 Configuring Interface Characteristics  
Understanding Interface Types  
Note  
The physical switch ports can be 10/100/1000 Ethernet ports, 100BASE-FX ports, 1000BASE-SX ports,  
or small form-factor pluggable (SFP)-module ports. For more information, see the switch hardware  
installation guide.  
These sections describes these types of interfaces:  
•
•
•
•
•
Access Ports, page 7-2  
Trunk Ports, page 7-2  
Port-Based VLANs, page 7-3  
EtherChannel Port Groups, page 7-3  
Connecting Interfaces, page 7-4  
Access Ports  
An access port belongs to and carries the traffic of only one VLAN (unless it is configured as a voice  
VLAN port). Traffic is received and sent in native formats with no VLAN tagging. Traffic arriving on  
an access port is assumed to belong to the VLAN assigned to the port. If an access port receives an  
IEEE 802.1p- or 802.1Q-tagged packet for the VLAN assigned to the port, the packet is forwarded. If  
the port receives an IEEE 802.1p- or IEEE 802.1Q-tagged packet for another VLAN, the packet is  
dropped, the source address is not learned, and the frame is counted in the No destination statistic.  
The switch does not support ISL-tagged packets. If the switch receives an ISL-tagged packet, the packet  
is flooded in the native VLAN of the port on which it was received because the MAC destination address  
in the ISL-tagged packet is a multicast address.  
Two types of access ports are supported:  
•
•
Static access ports are manually assigned to a VLAN.  
VLAN membership of dynamic access ports is learned through incoming packets. By default, a  
dynamic access port is a member of no VLAN, and forwarding to and from the port is enabled only  
when the VLAN membership of the port is discovered. Dynamic access ports on the switch are  
assigned to a VLAN by a VLAN Membership Policy Server (VMPS). The VMPS can be a  
Catalyst 6000 series switch; the switch does not support the function of a VMPS.  
Trunk Ports  
A trunk port carries the traffic of multiple VLANs and by default is a member of all VLANs in the VLAN  
database. Only IEEE 802.1Q trunk ports are supported. An IEEE 802.1Q trunk port supports  
simultaneous tagged and untagged traffic. An IEEE 802.1Q trunk port is assigned a default Port VLAN  
ID (PVID), and all untagged traffic travels on the port default PVID. All untagged traffic and tagged  
traffic with a NULL VLAN ID are assumed to belong to the port default PVID. A packet with a VLAN  
ID equal to the outgoing port default PVID is sent untagged. All other traffic is sent with a VLAN tag.  
Although by default, a trunk port is a member of every VLAN known to the VTP, you can limit VLAN  
membership by configuring an allowed list of VLANs for each trunk port. The list of allowed VLANs  
does not affect any other port but the associated trunk port.  
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Chapter 7 Configuring Interface Characteristics  
Understanding Interface Types  
All possible VLANs (VLAN ID 1 to 4094) can be in the allowed list. By default, the allowed list is  
different for the switch internal and external ports:  
•
•
•
VLAN ID range is 2 to 4094 on the internal 1000 Mbps ports  
VLAN ID range is 1 on the internal 100 Mbps management module ports  
VLAN ID range is 1 to 4094 on the external ports  
A trunk port can only become a member of a VLAN if VTP knows of the VLAN and the VLAN is in the  
enabled state. If VTP learns of a new, enabled VLAN and the VLAN is in the allowed list for a trunk  
port, the trunk port automatically becomes a member of that VLAN and traffic is forwarded to and from  
the trunk port for that VLAN. If VTP learns of a new, enabled VLAN that is not in the allowed list for  
a trunk port, the port does not become a member of the VLAN, and no traffic for the VLAN is forwarded  
to or from the port.  
For more information about trunk ports, see Chapter 12, “Configuring VLANs.”  
Port-Based VLANs  
A VLAN is a switched network that is logically segmented by function, team, or application, without  
regard to the physical location of the users. For more information about VLANs, see Chapter 12,  
“Configuring VLANs.” Packets received on a port are forwarded only to ports that belong to the same  
VLAN as the receiving port. Network devices in different VLANs cannot communicate with one another  
without a Layer 3 device to route traffic between the VLANs.  
VLAN partitions provide hard firewalls for traffic in the VLAN, and each VLAN has its own MAC  
address table. A VLAN comes into existence when a local port is configured to be associated with the  
VLAN, when the VLAN Trunking Protocol (VTP) learns of its existence from a neighbor on a trunk, or  
when a user creates a VLAN.  
To configure normal-range VLANs (VLAN IDs 1 to 1005), use the vlan vlan-id global configuration  
command to enter config-vlan mode or the vlan database privileged EXEC command to enter VLAN  
configuration mode. The VLAN configurations for VLAN IDs 1 to 1005 are saved in the VLAN  
database. To configure extended-range VLANs (VLAN IDs 1006 to 4094), you must use config-vlan  
mode with VTP mode set to transparent. Extended-range VLANs are not added to the VLAN database.  
When VTP mode is transparent, the VTP and VLAN configuration is saved in the switch running  
configuration, and you can save it in the switch startup configuration file by entering the copy  
running-config startup-config privileged EXEC command.  
Add ports to a VLAN by using the switchport interface configuration commands:  
•
•
•
Identify the interface.  
For a trunk port, set trunk characteristics, and if desired, define the VLANs to which it can belong.  
For an access port, set and define the VLAN to which it belongs.  
EtherChannel Port Groups  
EtherChannel port groups provide the ability to treat multiple switch ports as one switch port. These port  
groups act as a single logical port for high-bandwidth connections between switches or between switches  
and servers. An EtherChannel balances the traffic load across the links in the channel. If a link within  
the EtherChannel fails, traffic previously carried over the failed link changes to the remaining links. You  
can group multiple trunk ports into one logical trunk port or group multiple access ports into one logical  
access port. Most protocols operate over either single ports or aggregated switch ports and do not  
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Chapter 7 Configuring Interface Characteristics  
Using the Interface Command  
recognize the physical ports within the port group. Exceptions are the DTP, the Cisco Discovery  
Protocol (CDP), the Port Aggregation Protocol (PAgP), and Link Aggregation Control Protocol (LACP)  
which operate only on physical ports.  
When you configure an EtherChannel, you create a port-channel logical interface and assign an interface  
to the EtherChannel. For Layer 2 interfaces, the logical interface is dynamically created. You manually  
assign an interface to the EtherChannel by using the channel-group interface configuration command.  
This command binds the physical and logical ports together. For more information, see Chapter 24,  
“Configuring EtherChannels and Layer 2 Trunk Failover.”  
Connecting Interfaces  
Devices within a single VLAN can communicate directly through any switch. Ports in different VLANs  
cannot exchange data without going through a routing device or routed interface.  
With a standard Layer 2 switch, ports in different VLANs have to exchange information through a  
router. In the configuration shown in Figure 7-1, when Host A in VLAN 20 sends data to Host B in  
VLAN 30, it must go from Host A to the switch, to the router, back to the switch, and then to Host B.  
Figure 7-1  
Connecting VLANs with Layer 2 Switches  
Cisco router  
VLAN 20  
VLAN 30  
BladeCenter  
Using the Interface Command  
To configure a physical interface (port), use the interface global configuration command to enter interface  
configuration mode and to specify the interface type, slot, and number.  
•
Type—Fast Ethernet (fastethernet or fa) for 10/100 Ethernet or Gigabit Ethernet (gigabitethernet or  
gi) Each switch platform supports different types of interfaces. To display a complete list of the  
interface types supported on your switch, use the interface ? global configuration command.  
•
•
Slot—The slot number on the switch (always 0 on this switch).  
Port number—The interface number on the switch. The port numbers always begin at 1, starting  
with the leftmost port when facing the front of the switch, for example, fastethernet0/1,  
fastethernet0/2. If there is more than one interface type (for example, 10/100 ports and Gigabit  
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Chapter 7 Configuring Interface Characteristics  
Using the Interface Command  
Ethernet ports), the port number restarts with the second interface type: gigabitethernet0/1,  
gigabitethernet0/2. The interface notation for switch ports 1 to 20 is interface gigabitethernet  
(such as interface gi).  
Switch ports 1 to 14 are internal 1000 Mbps connections to the other blades in the BladeCenter.  
These ports operate at 1000 Mbps in full-duplex mode.  
Switch ports 15 and 16 are internal 100 Mbps connections to the Management Module. These ports  
operate at 100 Mbps in full-duplex mode.  
Note  
You cannot change the speed and duplex settings on the internal ports 1 to 16.  
Switch ports 17 to 20 are for connections to external devices such as other switches. Depending on  
the switch model, you can change the speed and duplex settings on the external ports 17 to 20.  
You can identify physical interfaces by physically checking the interface location on the switch. You  
can also use the Cisco IOS show privileged EXEC commands to display information about a specific  
interface or all the interfaces on the switch. The remainder of this chapter primarily provides physical  
interface configuration procedures.  
This section describes how to configure all types of interfaces and how to configure a range of interfaces:  
•
•
•
Procedures for Configuring Interfaces, page 7-5  
Configuring a Range of Interfaces, page 7-6  
Configuring and Using Interface-Range Macros, page 7-7  
Procedures for Configuring Interfaces  
These general instructions apply to all interface configuration processes.  
Step 1  
Step 2  
Enter the configure terminal command at the privileged EXEC prompt:  
Switch# configure terminal  
Enter configuration commands, one per line. End with CNTL/Z.  
Switch(config)#  
Enter the interface global configuration command. Identify the interface type and the number of the  
connector. In this example, Gigabit Ethernet interface 0/17 is selected:  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)#  
Note  
You do not need to add a space between the interface type and interface number. For example,  
in the preceding line, you can specify either gigabitethernet 0/1, gigabitethernet0/1, gi 0/1, or  
gi0/1.  
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Chapter 7 Configuring Interface Characteristics  
Using the Interface Command  
Step 3  
Follow each interface command with the interface configuration commands your particular interface  
requires. The commands you enter define the protocols and applications that will run on the interface.  
The commands are collected and applied to the interface when you enter another interface command or  
enter end to return to privileged EXEC mode.  
You can also configure a range of interfaces by using the interface range or interface range macro  
global configuration commands. Interfaces configured in a range must be the same type and must be  
configured with the same feature options.  
Step 4  
After you configure an interface, verify its status by using the show privileged EXEC commands listed  
in the “Monitoring and Maintaining the Interfaces” section on page 7-13.  
Enter the show interfaces privileged EXEC command to see a list of all interfaces on or configured for  
the switch. A report is provided for each interface that the device supports or for the specified interface.  
Configuring a Range of Interfaces  
You can use the interface range global configuration command to configure multiple interfaces with the  
same configuration parameters. When you enter the interface-range configuration mode, all command  
parameters that you enter are attributed to all interfaces within that range until you exit this mode.  
Beginning in privileged EXEC mode, follow these steps to configure a range of interfaces with the  
same parameters:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface range {port-range | macro  
macro_name}  
Enter interface-range configuration mode by entering the range of  
interfaces (VLANs or physical ports) to be configured.  
•
•
•
•
You can use the interface range command to configure up to five  
port ranges or a previously defined macro.  
The macro variable is explained in the “Configuring and Using  
Interface-Range Macros” section on page 7-7.  
Each comma-separated port-range must consist of the same port  
type. You do not need to enter spaces before or after the comma.  
When you define a range, the space between the first port and the  
hyphen is required.  
Step 3  
You can now use the normal configuration commands to apply the  
configuration parameters to all interfaces in the range.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show interfaces [interface-id]  
copy running-config startup-config  
Verify the configuration of the interfaces in the range.  
(Optional) Save your entries in the configuration file.  
When using the interface range global configuration command, note these guidelines:  
Valid entries for port-range:  
•
–
–
vlan vlan-ID - vlan-ID, where VLAN ID is from 1 to 4094  
fastethernet slot/{first port} - {last port}, where slot is 0  
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Chapter 7 Configuring Interface Characteristics  
Using the Interface Command  
–
–
gigabitethernet slot/{first port} - {last port}, where slot is 0  
port-channel port-channel-number - port-channel-number, where port-channel-number is  
from 1 to 6  
•
•
You must add a space between the interface numbers and the hyphen when using the  
interface range command. For example, the command interface range fastethernet0/1 - 5 is a  
valid range; the command interface range fastethernet0/1-5 is not a valid range.  
The interface range command works only with VLAN interfaces that have been configured with  
the interface vlan command (the show running-config privileged EXEC command output shows  
the configured VLAN interfaces). VLAN interfaces that do not appear by using the show  
running-config command cannot be used with the interface range command.  
•
All interfaces in a range must be the same type; that is, all Fast Ethernet ports, all Gigabit Ethernet  
ports, all EtherChannel ports, or VLAN interfaces.  
This example shows how to use the interface range global configuration command to set the speed on  
Fast Ethernet interfaces 0/1 to 0/5 to 100 Mbps:  
Switch# configure terminal  
Switch(config)# interface range fastethernet0/1 - 5  
Switch(config-if-range)# speed 100  
This example shows how to use a comma to add different interface type strings to the range to enable all  
Fast Ethernet interfaces in the range 0/1 to 0/3 and Gigabit Ethernet interfaces 0/1 and 0/2:  
Switch# configure terminal  
Switch(config)# interface range fastethernet0/1 - 3, gigabitethernet0/1 - 2  
Switch(config-if-range)# no shutdown  
If you enter multiple configuration commands while you are in interface-range mode, each command is  
executed as it is entered. The commands are not batched together and executed after you exit  
interface-range mode. If you exit interface-range configuration mode while the commands are being  
executed, some commands might not be executed on all interfaces in the range. Wait until the command  
prompt reappears before exiting interface-range configuration mode.  
Configuring and Using Interface-Range Macros  
You can create an interface-range macro to automatically select a range of interfaces for configuration.  
Before you can use the macro keyword in the interface range macro global configuration command  
string, you must use the define interface-range global configuration command to define the macro.  
Beginning in privileged EXEC mode, follow these steps to define an interface-range macro:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
define interface-range macro_name  
Define the interface-range macro, and save it in NVRAM.  
interface-range  
•
•
The macro_name is a 32-character maximum character string.  
A macro can contain up to five comma-separated interface ranges.  
You do not need to enter spaces before or after the comma.  
•
Each interface-range must consist of the same port type.  
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Using the Interface Command  
Command  
Purpose  
Step 3  
interface range macro macro_name  
Select the interface range to be configured by using the values saved  
in the interface-range macro called macro_name.  
You can now use the normal configuration commands to apply the  
configuration to all interfaces in the defined macro.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show running-config | include define  
copy running-config startup-config  
Show the defined interface-range macro configuration.  
(Optional) Save your entries in the configuration file.  
Use the no define interface-range macro_name global configuration command to delete a macro.  
When using the define interface-range global configuration command, note these guidelines:  
•
Valid entries for interface-range:  
–
–
–
–
vlan vlan-ID - vlan-ID, where VLAN ID is from 1 to 4094  
fastethernet slot/{first port} - {last port}, where slot is 0  
gigabitethernet slot/{first port} - {last port}, where slot is 0  
port-channel port-channel-number - port-channel-number, where port-channel-number is  
from 1 to 6.  
•
•
You must add a space between the interface numbers and the hyphen when entering an  
interface-range. For example, fastethernet 0/1 - 5 is a valid range; fastethernet 0/1-5 is not a valid  
range.  
The VLAN interfaces must have been configured with the interface vlan command. The show  
running-config privileged EXEC command output shows the configured VLAN interfaces. VLAN  
interfaces that do not appear by using the show running-config command cannot be used as  
interface-ranges.  
•
All interfaces in a range must be the same type; that is, all Fast Ethernet ports, all Gigabit Ethernet  
ports, all EtherChannel ports, or all VLANs, but you can combine multiple interface types in a  
macro.  
This example shows how to define an interface-range macro named enet_list to select Fast Ethernet  
ports 1 to 4 and to verify the macro configuration:  
Switch# configure terminal  
Switch(config)# define interface-range enet_list fastethernet0/1 - 4  
Switch(config)# end  
Switch# show running-config | include define  
define interface-range enet_list FastEthernet0/1 - 4  
This example shows how to create a multiple-interface macro named macro1:  
Switch# configure terminal  
Switch(config)# define interface-range macro1 gigabitethernet0/1 - 2, fastethernet0/5 - 7  
Switch(config)# end  
Switch#  
This example shows how to enter interface range configuration mode for the interface-range macro  
enet_list:  
Switch# configure terminal  
Switch(config)# interface range macro enet_list  
Switch(config-if-range)#  
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Chapter 7 Configuring Interface Characteristics  
Configuring Ethernet Interfaces  
This example shows how to delete the interface-range macro enet_list and to verify that it has been  
deleted.  
Switch# configure terminal  
Switch(config)# no define interface-range enet_list  
Switch# show run | include define  
Configuring Ethernet Interfaces  
The switch supports these interface types:  
•
•
•
Physical ports—Switch ports, including access and trunk ports  
Port channels—EtherChannel of interfaces  
VLANs  
These sections describe the default interface configuration and the optional features that you can  
configure on most physical interfaces:  
•
•
•
Default Ethernet Interface Configuration, page 7-9  
Configuring Interface Speed and Duplex Mode, page 7-10  
Adding a Description for an Interface, page 7-12  
Default Ethernet Interface Configuration  
Table 7-1 shows the Ethernet interface default configuration. For more details on the VLAN parameters  
listed in the table, see Chapter 12, “Configuring VLANs.” For details on controlling traffic to the port,  
see Chapter 15, “Configuring Port-Based Traffic Control.”  
Table 7-1  
Default Ethernet Interface Configuration  
Feature  
Default Setting  
Operating mode  
Layer 2.  
Allowed VLAN range  
VLAN ID range is 2 to 4094 on the internal 1000 Mbps ports  
(ports 1 to 14).  
VLAN ID range is 1 on the internal 100 Mbps management  
module ports (ports 15 and 16).  
VLAN ID range is 2 on the external ports (ports 17 to 20).  
VLAN 2 on the internal 1000 Mbps ports (ports 1 to 14)  
Default VLAN (for access ports)  
Native VLAN 1 on the internal 100 Mbps management  
module ports (ports 15 and 16)  
VLAN 1 on the external ports (ports 17 to 20).  
VLAN 2.  
Native VLAN (for IEEE 802.1Q  
trunks)  
VLAN trunking  
Port enable state  
Switchport mode dynamic desirable (supports DTP).  
All ports are enabled. See the installation guide for  
information about changing this value.  
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Chapter 7 Configuring Interface Characteristics  
Configuring Ethernet Interfaces  
Table 7-1  
Default Ethernet Interface Configuration (continued)  
Feature  
Default Setting  
Port description  
blade n for the internal 1000 Mbps ports (ports 1 to 14).  
mgmt 1 or 2 for the internal 100 Mbps management module  
ports (ports 15 and 16).  
extern n for the external ports (ports 17 to 20).  
Speed  
1000 for the internal 1000 Mbps ports (ports 1 to 14).  
100 for the internal 100 Mbps management module ports  
(ports 15 and 16).  
Autonegotiate for the external ports (ports 17 to 20).  
The speed on the internal ports is nonconfigurable.  
Full duplex for the internal 1000 Mbps ports (ports 1 to 14).  
Duplex mode  
Full duplex for the internal 100 Mbps management module  
ports (ports 15 and 16).  
Autonegotiate for the external ports (ports 17 to 20).  
The duplex mode on internal ports is nonconfigurable.  
Disabled on all Ethernet ports. See Chapter 24, “Configuring  
EtherChannel (PAgP) and Link  
Aggregation Control Protocol (LACP) EtherChannels and Layer 2 Trunk Failover.”  
Port blocking—unknown multicast and Disabled (not blocked).  
unknown unicast traffic  
Broadcast, multicast, and unicast storm Disabled. See the “Default Storm Control Configuration”  
control  
section on page 15-2.  
Protected port  
Disabled. See the “Configuring Protected Ports” section on  
page 15-3.  
Port security  
Port Fast  
Disabled. See the “Default Port Security Configuration”  
section on page 15-6.  
Enabled on ports 1 to 14.  
Disabled on ports 15 to 20.  
SFP module preferred.  
Media Type  
Configuring Interface Speed and Duplex Mode  
By default, the non-SFP module external ports (ports 17 to 20) are set to autonegotiate in speed and  
duplex mode. Depending on the switch model, you can change the speed and duplex settings of the  
external ports. The internal Gigabit Ethernet ports (ports 1 to 14) operate only at 1000 Mbps, full duplex.  
The internal 100 Mbps management module ports (ports 15 and 16) operate only at 100 Mbps, full  
duplex. You cannot configure the speed and duplex mode on the internal ports.  
In full-duplex mode, two stations can send and receive at the same time. When packets can flow in both  
directions simultaneously, effective Ethernet bandwidth doubles to 20 Mbps for 10-Mbps interfaces,  
to 200 Mbps for Fast Ethernet interfaces, and to 2 Gbps for Gigabit Ethernet interfaces. Full-duplex  
communication is often an effective solution to collisions, which are major constrictions in Ethernet  
networks. Normally, 10-Mbps ports operate in half-duplex mode, which means that stations can either  
receive or send.  
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Chapter 7 Configuring Interface Characteristics  
Configuring Ethernet Interfaces  
You can configure interface speed on the Gigabit Ethernet (10/100/1000 Mbps). You cannot configure  
speed on the fiber-optic SFP-module interfaces.  
These sections describe how to configure the interface speed and duplex mode:  
•
•
•
Configuration Guidelines, page 7-11  
Setting the Interface Speed and Duplex Parameters, page 7-11  
Adding a Description for an Interface, page 7-12  
Configuration Guidelines  
When configuring an interface speed and duplex mode, note these guidelines:  
•
•
Ethernet ports set to 1000 Mbps should always be set to full duplex.  
A Gigabit Ethernet port that does not match the settings of an attached device can lose connectivity  
and does not generate statistics.  
•
•
If both ends of the line support autonegotiation, we highly recommend the default setting of auto.  
When connecting an interface to a 100BASE-T device that does not autonegotiate, set the speed to  
a nonautonegotiation value (for example, nonegotiate), and set the duplex mode to full or half to  
match the device. The speed value and duplex mode must be explicitly set.  
•
•
When connecting an interface to a Gigabit Ethernet device that does not autonegotiate, disable  
autonegotiation on the switch, and set the duplex parameter to be compatible with the remote device.  
Fiber-optic SFP-module ports operate only at 1000 Mbps in full-duplex mode.  
Caution  
Changing the interface speed and duplex mode configuration might shut down and re-enable the  
interface during the reconfiguration.  
Setting the Interface Speed and Duplex Parameters  
Beginning in privileged EXEC mode, follow these steps to set the speed and duplex mode for a physical  
interface on a switch:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Enter interface configuration mode and the physical interface  
identification.  
Step 3  
Step 4  
Step 5  
speed {10 | 100 | 1000 | auto [10 | 100 |  
1000] | nonegotiate}  
Enter the appropriate speed parameter for the interface, or enter auto  
or nonegotiate.  
Note  
This option is available only on the external ports. It is not  
available on the internal switch ports.  
duplex {auto | full | half}  
Enter the duplex parameter for the interface. For configuration  
guidelines, see the “Configuration Guidelines” section on page 7-11.  
Note  
This option is available only on the external ports. It is not  
available on the internal switch ports.  
end  
Return to privileged EXEC mode.  
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Chapter 7 Configuring Interface Characteristics  
Configuring Ethernet Interfaces  
Command  
Purpose  
Step 6  
Step 7  
show interfaces interface-id  
Display the interface speed and duplex mode configuration.  
(Optional) Save your entries in the configuration file.  
copy running-config startup-config  
Use the no speed and no duplex interface configuration commands to return the interface to the default  
speed and duplex settings (autonegotiate). To return all interface settings to the defaults, use the default  
interface interface-id interface configuration command.  
This example shows how to set the interface speed to 10 Mbps and the duplex mode to half on Gigabit  
Ethernet interface 0/17 and to verify the configuration:  
Switch# configure terminal  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# speed 10  
Switch(config-if)# duplex half  
Switch(config)# end  
Switch# show running-config  
Building configuration...  
Current configuration : 1954 bytes  
!
version 12.1  
no service pad  
service timestamps debug uptime  
service timestamps log uptime  
no service password-encryption  
!
hostname Switch  
!
<output truncated>  
!
interface gigabitethernet0/17  
switchport mode trunk  
no ip address  
duplex half  
speed 10  
!
<output truncated>  
Adding a Description for an Interface  
You can add a description about an interface to help you remember its function. The description appears  
in the output of these commands: show configuration, show running-config, and show interfaces.  
Beginning in privileged EXEC mode, follow these steps to add a description for an interface:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode  
interface interface-id  
Enter interface configuration mode, and enter the interface for which  
you are adding a description.  
Step 3  
Step 4  
description string  
Add a description (up to 240 characters) for an interface.  
Return to privileged EXEC mode.  
end  
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Chapter 7 Configuring Interface Characteristics  
Monitoring and Maintaining the Interfaces  
Command  
Purpose  
Step 5  
show interfaces interface-id description Verify your entry.  
or  
show running-config  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Use the no description interface configuration command to delete the description.  
This example shows how to add a description on a port and to verify the description:  
Switch# configure terminal  
Enter configuration commands, one per line. End with CNTL/Z.  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# description Connects to Marketing  
Switch(config-if)# end  
Switch# show interfaces gigabitethernet0/17 description  
Interface Status  
Gi0/17 up  
Protocol Description  
down Connects to Marketing  
Monitoring and Maintaining the Interfaces  
You can perform the tasks in these sections to monitor and maintain interfaces:  
•
•
•
Monitoring Interface and Controller Status, page 7-13  
Clearing and Resetting Interfaces and Counters, page 7-15  
Shutting Down and Restarting the Interface, page 7-15  
Monitoring Interface and Controller Status  
Commands entered at the privileged EXEC prompt display information about the interface, including  
the version of the software and the hardware, the controller status, and statistics about the interfaces.  
Table 7-2 lists some of these interface monitoring commands. (You can display the full list of show  
commands by using the show ? command at the privileged EXEC prompt.) These commands are fully  
described in the Cisco IOS Interface Command Reference for Cisco IOS Release 12.1.  
Table 7-2  
show Commands for Interfaces  
Command  
Purpose  
show interfaces [interface-id]  
Display the status and configuration of all interfaces or a specific  
interface.  
show interfaces [interface-id] capabilities [module Display the capabilities of an interface. The module number is always  
{module-number}] 0. If you enter an interface ID, the module keyword is not visible.  
show interfaces interface-id status [err-disabled] Display interface status or a list of interfaces in error-disabled state.  
show interfaces [interface-id] switchport  
Display administrative and operational status of switching  
(nonrouting) ports.  
show interfaces [interface-id] description  
Display the description configured on an interface or all interfaces and  
the interface status.  
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Chapter 7 Configuring Interface Characteristics  
Monitoring and Maintaining the Interfaces  
Table 7-2  
show Commands for Interfaces (continued)  
Command  
Purpose  
show ip interface [interface-id]  
Display the usability status of all interfaces configured for IP or the  
specified interface.  
show interfaces transceiver properties  
show running-config interface [interface-id]  
show version  
(Optional) Display speed and duplex settings on the interface.  
Display the running configuration in RAM for the interface.  
Display the hardware configuration, software version, the names and  
sources of configuration files, and the boot images.  
This example shows how to display the status of switching ports:  
Switch# show interfaces gigabitethernet 0/1 switchport  
Name: Gi0/1  
Switchport: Enabled  
Administrative Mode: trunk  
Operational Mode: trunk  
Administrative Trunking Encapsulation: dot1q  
Operational Trunking Encapsulation: dot1q  
Negotiation of Trunking: On  
Access Mode VLAN: 2 (VLAN0002)  
Trunking Native Mode VLAN: 2 (VLAN0002)  
Voice VLAN: none  
Administrative private-vlan host-association: none  
Administrative private-vlan mapping: none  
Administrative private-vlan trunk native VLAN: none  
Administrative private-vlan trunk encapsulation: dot1q  
Administrative private-vlan trunk normal VLANs: none  
Administrative private-vlan trunk private VLANs: none  
Operational private-vlan: none  
Trunking VLANs Enabled: 2-4094  
Pruning VLANs Enabled: 2-1001  
Capture Mode Disabled  
Capture VLANs Allowed: ALL  
Protected: false  
Appliance trust: none  
Switch#  
This example shows how to display the running configuration of Gigabit Ethernet interface 17:  
Switch# show running-config interface gigabitethernet0/17  
Building configuration...  
Current configuration : 156 bytes  
!
interface GigabitEthernet0/17  
description extern1  
switchport access vlan 2  
switchport trunk native vlan 2  
ip access-group SecWiz_Gi0_1_out_ip in  
end  
For additional examples of the show interfaces privileged EXEC command output, see the command  
reference for this release.  
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Chapter 7 Configuring Interface Characteristics  
Monitoring and Maintaining the Interfaces  
Clearing and Resetting Interfaces and Counters  
Table 7-3 lists the privileged EXEC mode clear commands that you can use to clear counters and reset  
interfaces.  
Table 7-3  
Clear Commands for Interfaces  
Command  
Purpose  
clear counters [interface-id]  
Clear interface counters.  
clear interface interface-id  
Reset the hardware logic on an interface.  
Reset the hardware logic on an asynchronous serial line.  
clear line [number | console 0 | vty number]  
To clear the interface counters shown by the show interfaces privileged EXEC command, use the clear  
counters privileged EXEC command. The clear counters command clears all current interface counters  
from the interface unless optional arguments are specified to clear only a specific interface type from a  
specific interface number.  
Note  
The clear counters privileged EXEC command does not clear counters retrieved by using Simple  
Network Management Protocol (SNMP), but only those seen with the show interfaces privileged EXEC  
command output.  
This example shows how to clear and reset the counters on a port:  
Switch# clear counters gigabitethernet0/17  
Clear "show interface" counters on this interface [confirm] y  
Switch#  
*Sep 30 08:42:55: %CLEAR-5-COUNTERS: Clear counter on interface gigabitethernet0/17  
by vty1 (171.69.115.10)  
Use the clear interface or clear line privileged EXEC command to clear and reset an interface or serial  
line. Under most circumstances, you do not need to clear the hardware logic on interfaces or serial lines.  
This example shows how to clear and reset a port:  
Switch# clear interface gigabitethernet0/17  
Shutting Down and Restarting the Interface  
Shutting down an interface disables all functions on the specified interface and marks the interface as  
unavailable on all monitoring command displays. This information is communicated to other network  
servers through all dynamic routing protocols. The interface is not mentioned in any routing updates.  
Beginning in privileged EXEC mode, follow these steps to shut down an interface:  
Command  
configure terminal  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
interface {vlan vlan-id} | {{fastethernet | gigabitethernet} Select the interface to be configured.  
interface-id} | {port-channel port-channel-number}  
Step 3  
shutdown  
Shut down an interface.  
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Chapter 7 Configuring Interface Characteristics  
Monitoring and Maintaining the Interfaces  
Command  
Purpose  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entry.  
show running-config  
Use the no shutdown interface configuration command to restart the interface.  
This example shows how to shut down a port:  
Switch# configure terminal  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# shutdown  
Switch(config-if)#  
*Sep 30 08:33:47: %LINK-5-CHANGED: Interface GigabitEthernet0/17, changed state to a  
administratively down  
This example shows how to re-enable a port:  
Switch# configure terminal  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# no shutdown  
Switch(config-if)#  
*Sep 30 08:36:00: %LINK-3-UPDOWN: Interface GigabitEthernet0/17, changed state to up  
To verify that an interface is disabled, enter the show interfaces privileged EXEC command. A disabled  
interface appears as administratively down in the show interfaces command output.  
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C H A P T E R  
8
Configuring Smartports Macros  
This chapter describes how to configure and apply Smartports macros on the Cisco Systems Intelligent  
Gigabit Ethernet Switch Module.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
This chapter consists of these sections:  
•
•
•
Understanding Smartports Macros, page 8-1  
Configuring Smartports Macros, page 8-2  
Displaying Smartports Macros, page 8-8  
Understanding Smartports Macros  
Smartports macros provide a convenient way to save and share common configurations. You can use  
Smartports macros to enable features and settings based on the location of a switch in the network and  
for mass configuration deployments across the network.  
Each Smartports macro is a set of CLI commands that you define. Smartports macros do not contain new  
CLI commands; they are simply a group of existing CLI commands.  
When you apply a Smartports macro on an interface, the CLI commands within the macro are configured  
on the interface. When the macro is applied to an interface, the existing interface configurations are not  
lost. The new commands are added to the interface and are saved in the running configuration file.  
There are Cisco-default Smartports macros embedded in the switch software (see Table 8-1). You can  
display these macros and the commands they contain by using the show parser macro user EXEC  
command.  
Table 8-1  
Cisco-Default Smartports Macros  
Macro Name1  
Description  
cisco-global  
Use this global configuration macro to enable load balancing across VLANs, provide  
rapid convergence of spanning-tree instances and to enable port error recovery.  
cisco-desktop Use this interface configuration macro for increased network security and reliability  
when connecting a desktop device, such as a PC, to a switch port.  
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Chapter 8 Configuring Smartports Macros  
Configuring Smartports Macros  
Table 8-1  
Cisco-Default Smartports Macros (continued)  
Macro Name1  
Description  
cisco-switch  
Use this interface configuration macro when connecting an access switch and a  
distribution switch.  
cisco-router  
Use this interface configuration macro when connecting the switch and a WAN  
router.  
cisco-wireless Use this interface configuration macro when connecting the switch and a wireless  
access point.  
1. Cisco-default Smartports macros vary depending on the software version running on your switch.  
Cisco also provides a collection of pretested, Cisco-recommended baseline configuration templates for  
Catalyst switches and Cisco Systems Intelligent Gigabit Ethernet Switch Modules. The online reference  
guide templates provide the CLI commands that you can use to create Smartports macros based on the  
usage of the port. You can use the configuration templates to create Smartports macros to build and  
deploy Cisco-recommended network designs and configurations. For more information about  
Cisco-recommended configuration templates, see this Smartports website:  
http://www.cisco.com/go/smartports  
Configuring Smartports Macros  
You can create a new Smartports macro or use an existing macro as a template to create a new macro  
that is specific to your application. After you create the macro, you can apply it globally to a switch or  
to a switch interface or range of interfaces.  
This section includes information about:  
•
•
•
•
•
Default Smartports Macro Configuration, page 8-2  
Smartports Macro Configuration Guidelines, page 8-2  
Creating Smartports Macros, page 8-4  
Applying Smartports Macros, page 8-5  
Applying Cisco-Default Smartports Macros, page 8-6  
Default Smartports Macro Configuration  
There are no Smartports macros enabled.  
Smartports Macro Configuration Guidelines  
Follow these guidelines when configuring macros on your switch:  
•
When creating a macro, do not use the exit or end commands or change the command mode by using  
interface interface-id. This could cause commands that follow exit, end, or interface interface-id  
to execute in a different command mode.  
•
When creating a macro, all CLI commands should be in the same configuration mode.  
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Chapter 8 Configuring Smartports Macros  
Configuring Smartports Macros  
•
When creating a macro that requires the assignment of unique values, use the parameter value  
keywords to designate values specific to the interface. Keyword matching is case sensitive. All  
matching occurrences of the keyword are replaced with the corresponding value. Any full match of  
a keyword, even if it is part of a larger string, is considered a match and is replaced by the  
corresponding value.  
•
•
Macro names are case sensitive. For example, the commands macro name Sample-Macro and  
macro name sample-macro will result in two separate macros.  
Some macros might contain keywords that require a parameter value. You can use the macro global  
apply macro-name ? global configuration command or the macro apply macro-name ? interface  
configuration command to display a list of any required values in the macro. If you apply a macro  
without entering the keyword values, the commands are invalid and are not applied.  
•
•
When a macro is applied globally to a switch or to a switch interface, all existing configuration on  
the interface is retained. This is helpful when applying an incremental configuration.  
If you modify a macro definition by adding or deleting commands, the changes are not reflected on  
the interface where the original macro was applied. You need to reapply the updated macro on the  
interface to apply the new or changed commands.  
•
You can use the macro global trace macro-name global configuration command or the macro trace  
macro-name interface configuration command to apply and debug a macro to find any syntax or  
configuration errors. If a command fails because of a syntax error or a configuration error, the macro  
continues to apply the remaining commands.  
•
•
•
Some CLI commands are specific to certain interface types. If a macro is applied to an interface that  
does not accept the configuration, the macro will fail the syntax check or the configuration check,  
and the switch will return an error message.  
Applying a macro to an interface range is the same as applying a macro to a single interface. When  
you use an interface range, the macro is applied sequentially to each interface within the range. If a  
macro command fails on one interface, it is still applied to the remaining interfaces.  
When you apply a macro to a switch or a switch interface, the macro name is automatically added  
to the switch or interface. You can display the applied commands and macro names by using the  
show running-config user EXEC command.  
There are Cisco-default Smartports macros embedded in the switch software. You can display these  
macros and the commands they contain by using the show parser macro user EXEC command.  
Follow these guidelines when you apply a Cisco-default Smartports macro on an interface:  
•
Display all macros on the switch by using the show parser macro user EXEC command. Display  
the contents of a specific macro by using the show parser macro name macro-name user EXEC  
command.  
•
Keywords that begin with $ mean that a unique parameter value is required. Append the  
Cisco-default macro with the required values by using the parameter value keywords.  
The Cisco-default macros use the $ character to help identify required keywords. There is no  
restriction on using the $ character to define keywords when you create a macro.  
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Chapter 8 Configuring Smartports Macros  
Configuring Smartports Macros  
Creating Smartports Macros  
Beginning in privileged EXEC mode, follow these steps to create a Smartports macro:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
macro name macro-name  
Enter global configuration mode.  
Create a macro definition, and enter a macro name. A macro definition  
can contain up to 3000 characters.  
Enter the macro commands with one command per line. Use the @  
character to end the macro. Use the # character at the beginning of a line  
to enter comment text within the macro.  
(Optional) You can define keywords within a macro by using a help  
string to specify the keywords. Enter # macro keywords word to define  
the keywords that are available for use with the macro. Separated by a  
space, you can enter up to three help string keywords in a macro.  
Macro names are case sensitive. For example, the commands macro  
name Sample-Macro and macro name sample-macro will result in  
two separate macros.  
We recommend that you do not use the exit or end commands or change  
the command mode by using interface interface-id in a macro. This  
could cause any commands following exit, end, or interface  
interface-id to execute in a different command mode. For best results,  
all commands in a macro should be in the same configuration mode.  
Step 3  
Step 4  
end  
Return to privileged EXEC mode.  
Verify that the macro was created.  
show parser macro name macro-name  
The no form of the macro name global configuration command only deletes the macro definition. It  
does not affect the configuration of those interfaces on which the macro is already applied.  
This example shows how to create a macro that defines the switchport access VLAN and the number of  
secure MAC addresses and also includes two help string keywords by using # macro keywords:  
Switch(config)# macro name test  
switchport access vlan $VLANID  
switchport port-security maximum $MAX  
#macro keywords $VLANID $MAX  
@
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Chapter 8 Configuring Smartports Macros  
Configuring Smartports Macros  
Applying Smartports Macros  
Beginning in privileged EXEC mode, follow these steps to apply a Smartports macro:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
macro global {apply | trace}  
macro-name [parameter {value}]  
[parameter {value}] [parameter  
{value}]  
Apply each individual command defined in the macro to the switch by  
entering macro global apply macro-name. Specify macro global trace  
macro-name to apply and debug a macro to find any syntax or  
configuration errors.  
(Optional) Specify unique parameter values that are specific to the  
switch. You can enter up to three keyword-value pairs. Parameter  
keyword matching is case sensitive. All matching occurrences of the  
keyword are replaced with the corresponding value.  
Some macros might contain keywords that require a parameter value.  
You can use the macro global apply macro-name ? command to display  
a list of any required values in the macro. If you apply a macro without  
entering the keyword values, the commands are invalid and are not  
applied.  
Step 3  
Step 4  
macro global description text  
interface interface-id  
(Optional) Enter a description about the macro that is applied to the  
switch.  
(Optional) Enter interface configuration mode, and specify the interface  
on which to apply the macro.  
Step 5  
Step 6  
default interface interface-id  
(Optional) Clear all configuration from the specified interface.  
macro {apply | trace} macro-name  
[parameter {value}] [parameter  
{value}] [parameter {value}]  
Apply each individual command defined in the macro to the interface by  
entering macro apply macro-name. Specify macro trace macro-name  
to apply and debug a macro to find any syntax or configuration errors.  
(Optional) Specify unique parameter values that are specific to the  
interface. You can enter up to three keyword-value pairs. Parameter  
keyword matching is case sensitive. All matching occurrences of the  
keyword are replaced with the corresponding value.  
Some macros might contain keywords that require a parameter value.  
You can use the macro apply macro-name ? command to display a list  
of any required values in the macro. If you apply a macro without  
entering the keyword values, the commands are invalid and are not  
applied.  
Step 7  
macro description text  
(Optional) Enter a description about the macro that is applied to the  
interface.  
Step 8  
Step 9  
end  
Return to privileged EXEC mode.  
show parser macro description  
Verify that the macro is applied to the interface.  
[interface interface-id]  
Step 10  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
You can delete a global macro-applied configuration on a switch only by entering the no version of each  
command that is in the macro. You can delete a macro-applied configuration on an interface by entering  
the default interface interface-id interface configuration command.  
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Chapter 8 Configuring Smartports Macros  
Configuring Smartports Macros  
This example shows how to apply the user-created macro called snmp, to set the host name address to  
test-server and to set the IP precedence value to 7:  
Switch(config)# macro global apply snmp ADDRESS test-server VALUE 7  
This example shows how to debug the user-created macro called snmp by using the macro global trace  
global configuration command to find any syntax or configuration errors in the macro when it is applied  
to the switch.  
Switch(config)# macro global trace snmp VALUE 7  
Applying command...‘snmp-server enable traps port-security’  
Applying command...‘snmp-server enable traps linkup’  
Applying command...‘snmp-server enable traps linkdown’  
Applying command...‘snmp-server host’  
%Error Unknown error.  
Applying command...‘snmp-server ip precedence 7’  
This example shows how to apply the user-created macro called desktop-config and to verify the  
configuration.  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# macro apply desktop-config  
Switch(config-if)# end  
Switch# show parser macro description  
Interface  
--------------------------------------------------------------  
Gi0/20 desktop-config  
Macro Description  
--------------------------------------------------------------  
This example shows how to apply the user-created macro called desktop-config and to replace all  
occurrences of VLAN 1 with VLAN 25:  
Switch(config-if)# macro apply desktop-config vlan 25  
Applying Cisco-Default Smartports Macros  
Beginning in privileged EXEC mode, follow these steps to apply a Smartports macro:  
Command  
Purpose  
Step 1  
show parser macro  
Display the Cisco-default Smartports macros embedded in the switch  
software.  
Step 2  
Step 3  
Step 4  
show parser macro name macro-name  
Display the specific macro that you want to apply.  
Enter global configuration mode.  
configure terminal  
macro global {apply | trace}  
macro-name [parameter {value}]  
[parameter {value}] [parameter  
{value}]  
Append the Cisco-default macro with the required values by using the  
parameter value keywords and apply the macro to the switch.  
Keywords that begin with $ mean that a unique parameter value is  
required.  
You can use the macro global apply macro-name ? command to display  
a list of any required values in the macro. If you apply a macro without  
entering the keyword values, the commands are invalid and are not  
applied.  
Step 5  
Step 6  
interface interface-id  
(Optional) Enter interface configuration mode, and specify the interface  
on which to apply the macro.  
default interface interface-id  
(Optional) Clear all configuration from the specified interface.  
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Chapter 8 Configuring Smartports Macros  
Configuring Smartports Macros  
Command  
Purpose  
Step 7  
macro {apply | trace} macro-name  
[parameter {value}] [parameter  
{value}] [parameter {value}]  
Append the Cisco-default macro with the required values by using the  
parameter value keywords, and apply the macro to the interface.  
Keywords that begin with $ mean that a unique parameter value is  
required.  
You can use the macro apply macro-name ? command to display a list  
of any required values in the macro. If you apply a macro without  
entering the keyword values, the commands are invalid and are not  
applied.  
Step 8  
Step 9  
end  
Return to privileged EXEC mode.  
show running-config interface  
Verify that the macro is applied to an interface.  
interface-id  
Step 10  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
You can delete a global macro-applied configuration on a switch only by entering the no version of each  
command that is in the macro. You can delete a macro-applied configuration on an interface by entering  
the default interface interface-id interface configuration command.  
This example shows how to display the cisco-desktop macro, how to apply the macro, and to set the  
access VLAN ID to 25 on an interface:  
Switch# show parser macro cisco-desktop  
--------------------------------------------------------------  
Macro name : cisco-desktop  
Macro type : default  
# Basic interface - Enable data VLAN only  
# Recommended value for access vlan (AVID) should not be 1  
switchport access vlan $AVID  
switchport mode access  
# Enable port security limiting port to a single  
# MAC address -- that of desktop  
switchport port-security  
switchport port-security maximum 1  
# Ensure port-security age is greater than one minute  
# and use inactivity timer  
switchport port-security violation restrict  
switchport port-security aging time 2  
switchport port-security aging type inactivity  
# Configure port as an edge network port  
spanning-tree portfast  
spanning-tree bpduguard enable  
--------------------------------------------------------------  
Switch#  
Switch# configure terminal  
Switch(config)# gigabitethernet0/17  
Switch(config-if)# macro apply cisco-desktop $AVID 25  
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Chapter 8 Configuring Smartports Macros  
Displaying Smartports Macros  
Displaying Smartports Macros  
To display the Smartports macros, use one or more of the privileged EXEC commands in Table 8-2.  
Table 8-2  
Commands for Displaying Smartports Macros  
Command  
Purpose  
show parser macro  
Displays all configured macros.  
Displays a specific macro.  
show parser macro name macro-name  
show parser macro brief  
Displays the configured macro names.  
show parser macro description [interface  
interface-id]  
Displays the macro description for all interfaces or for a specified  
interface.  
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C H A P T E R  
9
Configuring STP  
This chapter describes how to configure the Spanning Tree Protocol (STP) on port-based VLANs on  
your Cisco Systems Intelligent Gigabit Ethernet Switch Module. The switch can use either the  
per-VLAN spanning-tree plus (PVST+) protocol based on the IEEE 802.1D standard and Cisco  
proprietary extensions, or the rapid per-VLAN spanning-tree plus (rapid-PVST+) protocol based on the  
IEEE 802.1w standard.  
For information about the Multiple Spanning Tree Protocol (MSTP) and how to map multiple VLANs  
to the same spanning-tree instance, see Chapter 10, “Configuring MSTP.”  
For information about other spanning-tree features such as Port Fast, UplinkFast, root guard, and so  
forth, see Chapter 11, “Configuring Optional Spanning-Tree Features.”  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
This chapter consists of these sections:  
•
•
•
Understanding Spanning-Tree Features, page 9-1  
Configuring Spanning-Tree Features, page 9-11  
Displaying the Spanning-Tree Status, page 9-23  
Understanding Spanning-Tree Features  
These sections describe how basic spanning-tree features work:  
•
•
•
•
•
•
•
•
•
STP Overview, page 9-2  
Spanning-Tree Topology and BPDUs, page 9-3  
Bridge ID, Switch Priority, and Extended System ID, page 9-4  
Spanning-Tree Interface States, page 9-4  
How a Switch or Port Becomes the Root Switch or Root Port, page 9-7  
Spanning Tree and Redundant Connectivity, page 9-8  
Spanning-Tree Address Management, page 9-8  
Accelerated Aging to Retain Connectivity, page 9-8  
Spanning-Tree Modes and Protocols, page 9-9  
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Chapter 9 Configuring STP  
Understanding Spanning-Tree Features  
•
•
•
Supported Spanning-Tree Instances, page 9-9  
Spanning-Tree Interoperability and Backward Compatibility, page 9-10  
STP and IEEE 802.1Q Trunks, page 9-10  
For configuration information, see the “Configuring Spanning-Tree Features” section on page 9-11.  
For information about optional spanning-tree features, see Chapter 11, “Configuring Optional  
Spanning-Tree Features.”  
STP Overview  
STP is a Layer 2 link management protocol that provides path redundancy while preventing loops in the  
network. For a Layer 2 Ethernet network to function properly, only one active path can exist between  
any two stations. Multiple active paths among end stations cause loops in the network. If a loop exists  
in the network, end stations might receive duplicate messages. Switches might also learn end-station  
MAC addresses on multiple Layer 2 interfaces. These conditions result in an unstable network.  
Spanning-tree operation is transparent to end stations, which cannot detect whether they are connected  
to a single LAN segment or a switched LAN of multiple segments.  
The STP uses a spanning-tree algorithm to select one switch of a redundantly connected network as the  
root of the spanning tree. The algorithm calculates the best loop-free path through a switched Layer 2  
network by assigning a role to each port based on the role of the port in the active topology:  
•
•
•
•
Root—A forwarding port elected for the spanning-tree topology  
Designated—A forwarding port elected for every switched LAN segment  
Alternate—A blocked port providing an alternate path to the root bridge in the spanning tree  
Backup—A blocked port in a loopback configuration  
The switch that has all of its ports as the designated role or as the backup role is the root switch. The  
switch that has at least one of its ports in the designated role is called the designated switch.  
Spanning tree forces redundant data paths into a standby (blocked) state. If a network segment in the  
spanning tree fails and a redundant path exists, the spanning-tree algorithm recalculates the  
spanning-tree topology and activates the standby path. Switches send and receive spanning-tree frames,  
called bridge protocol data units (BPDUs), at regular intervals. The switches do not forward these frames  
but use them to construct a loop-free path. BPDUs contain information about the sending switch and its  
ports, including switch and MAC addresses, switch priority, port priority, and path cost. Spanning tree  
uses this information to elect the root switch and root port for the switched network and the root port and  
designated port for each switched segment.  
When two interfaces on a switch are part of a loop, the spanning-tree port priority and path cost settings  
determine which interface is put in the forwarding state and which is put in the blocking state. The  
spanning-tree port priority value represents the location of an interface in the network topology and how  
well it is located to pass traffic. The path cost value represents the media speed.  
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Chapter 9 Configuring STP  
Understanding Spanning-Tree Features  
Spanning-Tree Topology and BPDUs  
The stable, active spanning-tree topology of a switched network is determined by these elements:  
•
•
•
The unique bridge ID (switch priority and MAC address) associated with each VLAN on each switch  
The spanning-tree path cost to the root switch  
The port identifier (port priority and MAC address) associated with each Layer 2 interface  
When the switches in a network are powered up, each functions as the root switch. Each switch sends a  
configuration BPDU through all of its ports. The BPDUs communicate and compute the spanning-tree  
topology. Each configuration BPDU contains this information:  
•
•
•
•
•
•
The unique bridge ID of the switch that the sending switch identifies as the root switch  
The spanning-tree path cost to the root  
The bridge ID of the sending switch  
Message age  
The identifier of the sending interface  
Values for the hello, forward-delay, and max-age protocol timers  
When a switch receives a configuration BPDU that contains superior information (lower bridge ID,  
lower path cost, and so forth), it stores the information for that port. If this BPDU is received on the root  
port of the switch, the switch also forwards it with an updated message to all attached LANs for which  
it is the designated switch.  
If a switch receives a configuration BPDU that contains inferior information to that currently stored for  
that port, it discards the BPDU. If the switch is a designated switch for the LAN from which the inferior  
BPDU was received, it sends that LAN a BPDU containing the up-to-date information stored for that  
port. In this way, inferior information is discarded, and superior information is propagated on the  
network.  
A BPDU exchange results in these actions:  
•
One switch in the network is elected as the root switch (the logical center of the spanning-tree  
topology in a switched network).  
For each VLAN, the switch with the highest switch priority (the lowest numerical priority value) is  
elected as the root switch. If all switches are configured with the default priority (32768), the switch  
with the lowest MAC address in the VLAN becomes the root switch. The switch priority value  
occupies the most significant bits of the bridge ID, as shown in Table 9-1 on page 9-4.  
•
A root port is selected for each switch (except the root switch). This port provides the best path  
(lowest cost) when the switch forwards packets to the root switch.  
•
•
The shortest distance to the root switch is calculated for each switch based on the path cost.  
A designated switch for each LAN segment is selected. The designated switch incurs the lowest path  
cost when forwarding packets from that LAN to the root switch. The port through which the  
designated switch is attached to the LAN is called the designated port.  
•
•
Interfaces included in the spanning-tree instance are selected. Root ports and designated ports are  
put in the forwarding state.  
All paths that are not needed to reach the root switch from anywhere in the switched network are  
placed in the spanning-tree blocking mode.  
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Chapter 9 Configuring STP  
Understanding Spanning-Tree Features  
Bridge ID, Switch Priority, and Extended System ID  
The IEEE 802.1D standard requires that each switch has an unique bridge identifier (bridge ID), which  
determines the selection of the root switch. Because each VLAN is considered as a different logical  
bridge with PVST+ and rapid PVST+, the same switch must have as many different bridge IDs as  
VLANs configured on it. Each VLAN on the switch has a unique 8-byte bridge ID; the two  
most-significant bytes are used for the switch priority, and the remaining six bytes are derived from the  
switch MAC address.  
The Cisco Systems Intelligent Gigabit Ethernet Switch Module support the IEEE 802.1t spanning-tree  
extensions. Some of the bits previously used for the switch priority are now used as the VLAN identifier.  
The result is that fewer MAC addresses are reserved for the switch, and a larger range of VLAN IDs can  
be supported, all while maintaining the uniqueness of the bridge ID. As shown in Table 9-1, the two  
bytes previously used for the switch priority are reallocated into a 4-bit priority value and a 12-bit  
extended system ID value equal to the VLAN ID.  
Table 9-1  
Switch Priority Value and Extended System ID  
Switch Priority Value  
Bit 16 Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1  
32768 16384 8192 4096 2048 1024 512 256 128 64 32 16  
Extended System ID (Set Equal to the VLAN ID)  
8
4
2
1
Spanning tree uses the extended system ID, the switch priority, and the allocated spanning-tree MAC  
address to make the bridge ID unique for each VLAN.  
Support for the extended system ID affects how you manually configure the root switch, the secondary  
root switch, and the switch priority of a VLAN. For example, when you change the switch priority value,  
you change the probability that the switch will be elected as the root switch. Configuring a higher value  
decreases the probability; a lower value increases the probability. For more information, see the  
“Configuring the Root Switch” section on page 9-15, the “Configuring a Secondary Root Switch”  
section on page 9-17, and the “Configuring the Switch Priority of a VLAN” section on page 9-20.  
Spanning-Tree Interface States  
Propagation delays can occur when protocol information passes through a switched LAN. As a result,  
topology changes can take place at different times and at different places in a switched network. When  
an interface transitions directly from nonparticipation in the spanning-tree topology to the forwarding  
state, it can create temporary data loops. Interfaces must wait for new topology information to propagate  
through the switched LAN before starting to forward frames. They must allow the frame lifetime to  
expire for forwarded frames that have used the old topology.  
Each Layer 2 interface on a switch using spanning tree exists in one of these states:  
•
•
Blocking—The interface does not participate in frame forwarding.  
Listening—The first transitional state after the blocking state when the spanning tree determines  
that the interface should participate in frame forwarding.  
•
•
•
Learning—The interface prepares to participate in frame forwarding.  
Forwarding—The interface forwards frames.  
Disabled—The interface is not participating in spanning tree because of a shutdown port, no link on  
the port, or no spanning-tree instance running on the port.  
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Chapter 9 Configuring STP  
Understanding Spanning-Tree Features  
An interface moves through these states:  
•
•
•
•
•
From initialization to blocking  
From blocking to listening or to disabled  
From listening to learning or to disabled  
From learning to forwarding or to disabled  
From forwarding to disabled  
Figure 9-1 illustrates how an interface moves through the states.  
Figure 9-1  
Spanning-Tree Interface States  
Power-on  
initialization  
Blocking  
state  
Listening  
state  
Disabled  
state  
Learning  
state  
Forwarding  
state  
When you power up the switch, spanning tree is enabled by default, and every interface in the switch,  
VLAN, or network goes through the blocking state and the transitory states of listening and learning.  
Spanning tree stabilizes each interface at the forwarding or blocking state.  
When the spanning-tree algorithm places a Layer 2 interface in the forwarding state, this process occurs:  
1. The interface is in the listening state while spanning tree waits for protocol information to transition  
the interface to the blocking state.  
2. While the spanning tree waits the forward-delay timer to expire, it moves the interface to the  
learning state and resets the forward-delay timer.  
3. In the learning state, the interface continues to block frame forwarding as the switch learns  
end-station location information for the forwarding database.  
4. When the forward-delay timer expires, spanning tree moves the interface to the forwarding state,  
where both learning and frame forwarding are enabled.  
Blocking State  
A Layer 2 interface in the blocking state does not participate in frame forwarding. After initialization, a  
BPDU is sent to each interface in the switch. A switch initially functions as the root until it exchanges  
BPDUs with other switches. This exchange establishes which switch in the network is the root or root  
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Chapter 9 Configuring STP  
Understanding Spanning-Tree Features  
switch. If there is only one switch in the network, no exchange occurs, the forward-delay timer expires,  
and the interfaces move to the listening state. An interface always enters the blocking state after switch  
initialization.  
An interface in the blocking state performs as follows:  
•
•
•
•
Discards frames received on the port  
Discards frames switched from another interface for forwarding  
Does not learn addresses  
Receives BPDUs  
Listening State  
Learning State  
Forwarding State  
The listening state is the first state a Layer 2 interface enters after the blocking state. The interface enters  
this state when the spanning tree determines that the interface should participate in frame forwarding.  
An interface in the listening state performs as follows:  
•
•
•
•
Discards frames received on the port  
Discards frames switched from another interface for forwarding  
Does not learn addresses  
Receives BPDUs  
A Layer 2 interface in the learning state prepares to participate in frame forwarding. The interface enters  
the learning state from the listening state.  
An interface in the learning state performs as follows:  
•
•
•
•
Discards frames received on the port  
Discards frames switched from another interface for forwarding  
Learns addresses  
Receives BPDUs  
A Layer 2 interface in the forwarding state forwards frames. The interface enters the forwarding state  
from the learning state.  
An interface in the forwarding state performs as follows:  
•
•
•
•
Receives and forwards frames received on the port  
Forwards frames switched from another port  
Learns addresses  
Receives BPDUs  
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Disabled State  
A Layer 2 interface in the disabled state does not participate in frame forwarding or in the spanning tree.  
An interface in the disabled state is nonoperational.  
A disabled interface performs as follows:  
•
•
•
•
Discards frames received on the port  
Discards frames switched from another interface for forwarding  
Does not learn addresses  
Does not receive BPDUs  
How a Switch or Port Becomes the Root Switch or Root Port  
If all switches in a network are enabled with default spanning-tree settings, the switch with the lowest  
MAC address becomes the root switch. In Figure 9-2, Switch A is elected as the root switch because the  
switch priority of all the switches is set to the default (32768) and Switch A has the lowest MAC address.  
However, because of traffic patterns, number of forwarding interfaces, or link types, Switch A might not  
be the ideal root switch. By increasing the priority (lowering the numerical value) of the ideal switch so  
that it becomes the root switch, you force a spanning-tree recalculation to form a new topology with the  
ideal switch as the root.  
Figure 9-2  
Spanning-Tree Topology  
DP  
DP  
DP  
A
D
RP  
DP  
DP  
RP  
B
RP  
C
RP = Root Port  
DP = Designated Port  
When the spanning-tree topology is calculated based on default parameters, the path between source and  
destination end stations in a switched network might not be ideal. For instance, connecting higher-speed  
links to an interface that has a higher number than the root port can cause a root-port change. The goal  
is to make the fastest link the root port.  
For example, assume that one port on Switch B is a Gigabit Ethernet link and that another port on  
Switch B (a 100 Mbps link) is the root port. Network traffic might be more efficient over the Gigabit  
Ethernet link. By changing the spanning-tree port priority on the Gigabit Ethernet interface to a higher  
priority (lower numerical value) than the root port, the Gigabit Ethernet interface becomes the new root  
port.  
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Understanding Spanning-Tree Features  
Spanning Tree and Redundant Connectivity  
You can create a redundant backbone with spanning tree by connecting two switch interfaces to another  
device or to two different devices. Spanning tree automatically disables one interface but enables it if  
the other one fails, as shown in Figure 9-3. If one link is high-speed and the other is low-speed, the  
low-speed link is always disabled. If the speeds are the same, the port priority and port ID are added  
together, and spanning tree disables the link with the lowest value.  
Figure 9-3  
Spanning Tree and Redundant Connectivity  
Switch A  
Catalyst 2950, 2955,  
or 3550 switch  
Catalyst 2950, 2955,  
or 3550 switch  
BladeCenter  
Switch B  
Active link  
Blocked link  
You can also create redundant links between switches by using EtherChannel groups. For more  
information, see Chapter 24, “Configuring EtherChannels and Layer 2 Trunk Failover.”  
Spanning-Tree Address Management  
IEEE 802.1D specifies 17 multicast addresses, ranging from 0x00180C2000000 to 0x0180C2000010, to  
be used by different bridge protocols. These addresses are static addresses that cannot be removed.  
Regardless of the spanning-tree state, the switch receives but does not forward packets destined for  
addresses between 0x0180C2000000 and 0x0180C200000F.  
If spanning tree is enabled, the switch CPU receives packets destined for 0x0180C2000000 and  
0x0180C2000010. If spanning-tree is disabled, the switch forwards those packets as unknown multicast  
addresses.  
Accelerated Aging to Retain Connectivity  
The default for aging dynamic addresses is 5 minutes, the default setting of the mac-address-table  
aging-time global configuration command. However, a spanning-tree reconfiguration can cause many  
station locations to change. Because these stations could be unreachable for 5 minutes or more during a  
reconfiguration, the address-aging time is accelerated so that station addresses can be dropped from the  
address table and then relearned. The accelerated aging is the same as the forward-delay parameter value  
(spanning-tree vlan vlan-id forward-time seconds global configuration command) when the spanning  
tree reconfigures.  
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Chapter 9 Configuring STP  
Understanding Spanning-Tree Features  
Because each VLAN is a separate spanning-tree instance, the switch accelerates aging on a per-VLAN  
basis. A spanning-tree reconfiguration on one VLAN can cause the dynamic addresses learned on that  
VLAN to be subject to accelerated aging. Dynamic addresses on other VLANs can be unaffected and  
remain subject to the aging interval entered for the switch.  
Spanning-Tree Modes and Protocols  
The switch supports these spanning-tree modes and protocols:  
PVST+—This spanning-tree mode is based on the IEEE 802.1D standard and Cisco proprietary  
extensions. The PVST+ runs on each VLAN on the switch up to the maximum supported, ensuring  
that each has a loop-free path through the network.  
The PVST+ provides Layer 2 load balancing for the VLAN on which it runs. You can create different  
logical topologies by using the VLANs on your network to ensure that all of your links are used but  
that no one link is oversubscribed. Each instance of PVST+ on a VLAN has a single root switch.  
This root switch propagates the spanning-tree information associated with that VLAN to all other  
switches in the network. Because each switch has the same information about the network, this  
process ensures that the network topology is maintained.  
•
Rapid PVST+—This spanning-tree mode is the same as PVST+ except that is uses a rapid  
convergence based on the IEEE 802.1w standard. It is the default spanning-tree mode used on all  
Ethernet, Fast Ethernet, and Gigabit Ethernet port-based VLANs. To provide rapid convergence, the  
rapid PVST+ immediately deletes dynamically learned MAC address entries on a per-port basis  
upon receiving a topology change. By contrast, PVST+ uses a short aging time for dynamically  
learned MAC address entries.  
The rapid PVST+ uses the same configuration as PVST+ (except where noted), and the switch needs  
only minimal extra configuration. The benefit of rapid PVST+ is that you can migrate a large PVST+  
install base to rapid PVST+ without having to learn the complexities of the MSTP configuration and  
without having to reprovision your network. In rapid-PVST+ mode, each VLAN runs its own  
spanning-tree instance up to the maximum supported.  
•
MSTP—This spanning-tree mode is based on the IEEE 802.1s standard. You can map multiple  
VLANs to the same spanning-tree instance, which reduces the number of spanning-tree instances  
required to support a large number of VLANs. The MSTP runs on top of the RSTP (based on IEEE  
802.1w, which provides for rapid convergence of the spanning tree by eliminating the forward delay  
and by quickly transitioning root ports and designated ports to the forwarding state. You cannot run  
MSTP without RSTP.  
The most common initial deployment of MSTP is in the backbone and distribution layers of a  
Layer 2 switched network. For more information, see Chapter 10, “Configuring MSTP.” For  
information about the number of supported spanning-tree instances, see the next section.  
Supported Spanning-Tree Instances  
In PVST+ or rapid-PVST+ mode, the switch supports up to 64 spanning-tree instances.  
In MSTP mode, the switch supports up to MST instances. The number of VLANs that can be mapped to  
a particular MST instance is unlimited.  
For information about how spanning tree interoperates with the VLAN Trunking Protocol (VTP), see the  
“Spanning-Tree Configuration Guidelines” section on page 9-12.  
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Chapter 9 Configuring STP  
Understanding Spanning-Tree Features  
Spanning-Tree Interoperability and Backward Compatibility  
Table 9-2 lists the interoperability and compatibility among the supported spanning-tree modes in a  
network.  
Table 9-2  
PVST+, MSTP, and Rapid-PVST+ Interoperability  
PVST+  
MSTP  
Rapid PVST+  
PVST+  
MSTP  
Yes  
Yes (with restrictions)  
Yes  
Yes (reverts to PVST+)  
Yes (reverts to PVST+)  
Yes  
Yes (with restrictions)  
Rapid PVST+ Yes (reverts to PVST+) Yes (reverts to PVST+)  
In a mixed MSTP and PVST+ network, the common spanning-tree (CST) root must be inside the MST  
backbone, and a PVST+ switch cannot connect to multiple MST regions.  
When a network contains switches running rapid PVST+ and switches running PVST+, we recommend  
that the rapid-PVST+ switches and PVST+ switches be configured for different spanning-tree instances.  
In the rapid-PVST+ spanning-tree instances, the root switch must be a rapid-PVST+ switch. In the  
PVST+ instances, the root switch must be a PVST+ switch. The PVST+ switches should be at the edge  
of the network.  
STP and IEEE 802.1Q Trunks  
The IEEE 802.1Q standard for VLAN trunks imposes some limitations on the spanning-tree strategy for  
a network. The standard requires only one spanning-tree instance for all VLANs allowed on the trunks.  
However, in a network of Cisco switches connected through IEEE 802.1Q trunks, the switches maintain  
one spanning-tree instance for each VLAN allowed on the trunks.  
When you connect a Cisco switch to a non-Cisco device through an IEEE 802.1Q trunk, the Cisco switch  
uses PVST+ to provide spanning-tree interoperability. If rapid PVST+ is enabled, the switch uses it  
instead of PVST+. The switch combines the spanning-tree instance of the IEEE 802.1Q VLAN of the  
trunk with the spanning-tree instance of the non-Cisco IEEE 802.1Q switch.  
However, all PVST+ or rapid-PVST+ information is maintained by Cisco switches separated by a cloud  
of non-Cisco IEEE 802.1Q switches. The non-Cisco IEEE 802.1Q cloud separating the Cisco switches  
is treated as a single trunk link between the switches.  
For more information on IEEE 802.1Q trunks, see Chapter 12, “Configuring VLANs.”  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Spanning Tree Considerations for Cisco Systems Intelligent Gigabit Ethernet  
Switch Modules  
A port-blocking filter exists between the switch external ports and the switch internal management  
module ports. This filter prevents operational traffic (such as unicast, multicast, and broadcast traffic)  
entering a switch external port from being forwarded to the management module, and from the  
management module to the external ports.  
However, STP does not recognize that this filter exists. During topology discovery, STP incorrectly  
perceives that an external port is forwarding operational traffic to the internal management module ports  
and that a Layer 2 loop exists. STP changes the state of the internal management module port to blocked  
state. This action is acceptable for operational traffic, but not for management (non-operational) traffic.  
The default path cost value on the switch internal management module ports is 100. The intent is to block  
operational traffic from being forwarded to the management module through any external port in the  
non-management VLAN. STP will see the cost of the management module port as the most expensive  
and block it. We do not recommend using the management module ports to carry operational traffic. This  
does not apply to the management VLAN on the management module ports. The switch prevents STP  
from blocking the management VLAN on the management module ports. STP blocking of VLANs on  
the management module ports is permitted for non-management VLANs only.  
Configuring Spanning-Tree Features  
These sections describe how to configure spanning-tree features:  
•
•
•
•
•
•
•
•
•
•
Default Spanning-Tree Configuration, page 9-12  
Spanning-Tree Configuration Guidelines, page 9-12  
Changing the Spanning-Tree Mode, page 9-13 (required)  
Disabling Spanning Tree, page 9-14 (optional)  
Configuring the Root Switch, page 9-15 (optional)  
Configuring a Secondary Root Switch, page 9-17 (optional)  
Configuring the Port Priority, page 9-17 (optional)  
Configuring the Path Cost, page 9-19 (optional)  
Configuring the Switch Priority of a VLAN, page 9-20 (optional)  
Configuring Spanning-Tree Timers, page 9-21 (optional)  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Default Spanning-Tree Configuration  
Table 9-3 shows the default spanning-tree configuration.  
Table 9-3  
Default Spanning-Tree Configuration  
Feature  
Default Setting  
Enable state  
Enabled on VLAN 1 (default management  
VLAN for the management module).  
Enabled on VLAN 2 (default operational  
traffic VLAN for the external ports and the  
internal Gigabit Ethernet ports).  
For more information, see the “Supported  
Spanning-Tree Instances” section on  
page 9-9.  
Spanning-tree mode  
Switch priority  
Rapid PVST+. (PVST+ and MSTP are  
disabled.)  
32768.  
Spanning-tree port priority (configurable on a per-interface basis)  
Spanning-tree port cost (configurable on a per-interface basis)  
128.  
1000 Mbps: 4.  
100 Mbps: 19.  
10 Mbps: 100.  
Spanning-tree VLAN port priority (configurable on a per-VLAN basis)  
Spanning-tree VLAN port cost (configurable on a per-VLAN basis)  
128.  
1000 Mbps: 4.  
100 Mbps: 19.  
10 Mbps: 100.  
Spanning-tree timers  
Hello time: 2 seconds.  
Forward-delay time: 15 seconds.  
Maximum-aging time: 20 seconds.  
Spanning-Tree Configuration Guidelines  
If more VLANs are defined in the VTP than there are spanning-tree instances, you can enable PVST+  
or rapid PVST+ on only 64 VLANs. If the number of VLANs exceeds 64, we recommend that you enable  
the MSTP to map multiple VLANs to a single spanning-tree instance. For more information, see the  
Chapter 10, “Configuring MSTP.”  
If 64 instances of spanning tree are already in use, you can disable spanning tree on one of the VLANs  
and then enable it on the VLAN where you want it to run. Use the no spanning-tree vlan vlan-id global  
configuration command to disable spanning tree on a specific VLAN, and use the spanning-tree vlan  
vlan-id global configuration command to enable spanning tree on the desired VLAN.  
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Configuring Spanning-Tree Features  
Caution  
Switches that are not running spanning tree still forward received BPDUs so that the other switches on  
the VLAN with a running spanning-tree instance can break loops. Therefore, spanning tree must be  
running on enough switches to break all the loops in the network. For example, at least one switch on  
each loop in the VLAN must be running spanning tree. It is not absolutely necessary to run spanning tree  
on all switches in the VLAN; however, if you are running spanning tree only on a minimal set of  
switches, an incautious change to the network that introduces another loop into the VLAN can result in  
a broadcast storm.  
Note  
If you have already used all available spanning-tree instances on your switch, adding another VLAN  
anywhere in the VTP domain creates a VLAN that is not running spanning tree on that switch. If you  
have the default allowed list on the trunk ports of that switch, the new VLAN is carried on all trunk ports.  
Depending on the topology of the network, this could create a loop in the new VLAN that will not be  
broken, particularly if there are several adjacent switches that have all run out of spanning-tree instances.  
You can prevent this possibility by setting up allowed lists on the trunk ports of switches that have used  
up their allocation of spanning-tree instances. Setting up allowed lists is not necessary in many cases and  
can make it more labor-intensive to add another VLAN to the network.  
Spanning-tree commands determine the configuration of VLAN spanning-tree instances. You create a  
spanning-tree instance when you assign an interface to a VLAN. The spanning-tree instance is removed  
when the last interface is moved to another VLAN. You can configure switch and port parameters before  
a spanning-tree instance is created; these parameters are applied when the spanning-tree instance is  
created.  
The switch supports PVST+, rapid PVST+, and MSTP, but only one version can be active at any time.  
(For example, all VLANs run PVST+, all VLANs run rapid PVST+, or all VLANs run MSTP.) For  
information about the different spanning-tree modes and how they interoperate, see the “Spanning-Tree  
Interoperability and Backward Compatibility” section on page 9-10.  
For configuration guidelines about UplinkFast and BackboneFast, see the “Optional Spanning-Tree  
Configuration Guidelines” section on page 11-10.  
Changing the Spanning-Tree Mode  
The switch supports three spanning-tree modes: PVST+, rapid PVST+, or MSTP. By default, the switch  
runs the PVST+ protocol.  
Beginning in privileged EXEC mode, follow these steps to change the spanning-tree mode. If you want  
to enable a mode that is different from the default mode, this procedure is required.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Configure a spanning-tree mode.  
spanning-tree mode {pvst | mst |  
rapid-pvst}  
•
•
Select pvst to enable PVST+ (the default setting).  
Select mst to enable MSTP (and RSTP). For more configuration  
steps, see Chapter 10, “Configuring MSTP.”  
•
Select rapid-pvst to enable rapid PVST+.  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Command  
Purpose  
Step 3  
interface interface-id  
(Recommended for rapid-PVST+ mode only) Specify an interface to  
configure, and enter interface configuration mode. Valid interfaces  
include physical ports, VLANs, and port channels. Valid VLAN IDs are  
1 to 4094. The port-channel range is 1 to 6.  
Step 4  
spanning-tree link-type point-to-point  
(Recommended for rapid-PVST+ mode only) Specify that the link type  
for this port is point-to-point.  
If you connect this port (local port) to a remote port through a  
point-to-point link and the local port becomes a designated port, the  
switch negotiates with the remote port and rapidly transitions the local  
port to the forwarding state.  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
clear spanning-tree detected-protocols (Recommended for rapid-PVST+ mode only) If any port on the switch  
is connected to a port on a legacy IEEE 802.1D switch, restart the  
protocol migration process on the entire switch.  
This step is optional if the designated switch determines that this switch  
is running rapid PVST+.  
Step 7  
Step 8  
show spanning-tree summary  
Verify your entries.  
and  
show spanning-tree interface  
interface-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return to the default setting, use the no spanning-tree mode global configuration command. To return  
the port to its default setting, use the no spanning-tree link-type interface configuration command.  
Disabling Spanning Tree  
Spanning tree is enabled by default on VLAN 1 and on all newly created VLANs up to the spanning-tree  
limit specified in the “Supported Spanning-Tree Instances” section on page 9-9. Disable spanning tree  
only if you are sure there are no loops in the network topology.  
Caution  
When spanning tree is disabled and loops are present in the topology, excessive traffic and indefinite  
packet duplication can drastically reduce network performance.  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Beginning in privileged EXEC mode, follow these steps to disable spanning tree on a per-VLAN basis.  
This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
no spanning-tree vlan vlan-id  
Disable spanning tree on a per-VLAN basis.  
For vlan-id, you can specify a single VLAN identified by VLAN ID  
number, a range of VLANs separated by a hyphen, or a series of VLANs  
separated by a comma. Valid interfaces include physical ports, VLANs,  
and port channels. The range is 1 to 4094.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree vlan vlan-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To re-enable spanning tree, use the spanning-tree vlan vlan-id global configuration command.  
Configuring the Root Switch  
The switch maintains a separate spanning-tree instance for each active VLAN configured on it. A bridge  
ID, consisting of the switch priority and the switch MAC address, is associated with each instance. For  
each VLAN, the switch with the lowest bridge ID becomes the root switch for that VLAN.  
To configure a switch to become the root for the specified VLAN, use the spanning-tree vlan vlan-id  
root global configuration command to modify the switch priority from the default value (32768) to a  
significantly lower value. When you enter this command, the switch checks the switch priority of the  
root switches for each VLAN. Because of the extended system ID support, the switch sets its own  
priority for the specified VLAN to 24576 if this value will cause this switch to become the root for the  
specified VLAN.  
If any root switch for the specified VLAN has a switch priority lower than 24576, the switch sets its own  
priority for the specified VLAN to 4096 less than the lowest switch priority. (4096 is the value of the  
least-significant bit of a 4-bit switch priority value as shown in Table 9-1 on page 9-4.)  
Note  
Note  
The spanning-tree vlan vlan-id root global configuration command fails if the value necessary to be the  
root switch is less than 1.  
If your network consists of switches that both do and do not support the extended system ID, it is unlikely  
that the switch with the extended system ID support will become the root switch. The extended system  
ID increases the switch priority value every time the VLAN number is greater than the priority of the  
connected switches running older software.  
Note  
The root switch for each spanning-tree instance should be a backbone or distribution switch. Do not  
configure an access switch as the spanning-tree primary root.  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Use the diameter keyword to specify the Layer 2 network diameter (that is, the maximum number of  
switch hops between any two end stations in the Layer 2 network). When you specify the network  
diameter, the switch automatically sets an optimal hello time, forward-delay time, and maximum-age  
time for a network of that diameter, which can significantly reduce the convergence time. You can use  
the hello keyword to override the automatically calculated hello time.  
Note  
After configuring the switch as the root switch, we recommend that you avoid manually configuring the  
hello time, forward-delay time, and maximum-age time by using the spanning-tree vlan vlan-id  
hello-time, spanning-tree vlan vlan-id forward-time, and the spanning-tree vlan vlan-id max-age  
global configuration commands.  
Beginning in privileged EXEC mode, follow these steps to configure a switch to become the root for the  
specified VLAN. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree vlan vlan-id root primary  
[diameter net-diameter [hello-time seconds]]  
Configure a switch to become the root for the specified VLAN.  
For vlan-id, you can specify a single VLAN identified by VLAN  
ID number, a range of VLANs separated by a hyphen, or a series  
of VLANs separated by a comma. Valid interfaces include  
physical ports, VLANs, and port channels. The range is 1 to 4094.  
•
(Optional) For diameter net-diameter, specify the maximum  
number of switches between any two end stations. The range  
is 2 to 7.  
•
(Optional) For hello-time seconds, specify the interval in  
seconds between the generation of configuration messages by  
the root switch. The range is 1 to 10 seconds; the default is 2  
seconds.  
Note  
When you enter this command without the optional  
keywords, the switch recalculates the forward-time,  
hello-time, max-age, and priority settings. If you had  
previously configured these parameters, the switch  
recalculates them.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree detail  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree vlan vlan-id root global  
configuration command.  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Configuring a Secondary Root Switch  
When you configure a Catalyst 2950 or Catalyst 2955 switch that supports the extended system ID as  
the secondary root, the switch priority is modified from the default value (32768) to 28672. The switch  
is then likely to become the root switch for the specified VLAN if the primary root switch fails. This is  
assuming that the other network switches use the default switch priority of 32768 and therefore are  
unlikely to become the root switch.  
You can execute this command on more than one switch to configure multiple backup root switches. Use  
the same network diameter and hello-time values as you used when you configured the primary root  
switch with the spanning-tree vlan vlan-id root primary global configuration command.  
Beginning in privileged EXEC mode, follow these steps to configure a switch to become the secondary  
root for the specified VLAN. This procedure is optional.  
Command  
configure terminal  
spanning-tree vlan vlan-id root secondary Configure a switch to become the secondary root for the specified  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
[diameter net-diameter [hello-time  
seconds]]  
VLAN.  
•
For vlan-id, you can specify a single VLAN identified by VLAN  
ID number, a range of VLANs separated by a hyphen, or a series  
of VLANs separated by a comma. Valid interfaces include  
physical ports, VLANs, and port channels. The range is 1 to  
4094.  
•
•
(Optional) For diameter net-diameter, specify the maximum  
number of switches between any two end stations. The range is  
2 to 7.  
(Optional) For hello-time seconds, specify the interval in  
seconds between the generation of configuration messages by  
the root switch. The range is 1 to 10 seconds; the default is 2  
seconds.  
Use the same network diameter and hello-time values that you used  
when configuring the primary root switch. See the “Configuring the  
Root Switch” section on page 9-15.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree detail  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree vlan vlan-id root global  
configuration command.  
Configuring the Port Priority  
If a loop occurs, spanning tree uses the port priority when selecting an interface to put into the  
forwarding state. You can assign higher priority values (lower numerical values) to interfaces that you  
want selected first and lower priority values (higher numerical values) that you want selected last. If all  
interfaces have the same priority value, spanning tree puts the interface with the lowest interface number  
in the forwarding state and blocks the other interfaces.  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Beginning in privileged EXEC mode, follow these steps to configure the port priority of an interface.  
This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify an interface to configure, and enter interface  
configuration mode.  
Valid interfaces include physical interfaces and  
port-channel logical interfaces (port-channel  
port-channel-number).  
Step 3  
spanning-tree port-priority priority  
Configure the port priority for an interface.  
For priority, the range is 0 to 240 in increments of 16. The  
default is 128. The lower the number, the higher the  
priority.  
Valid priority values are 0, 16, 32, 48, 64, 80, 96, 112, 128,  
144, 160, 176, 192, 208, 224, and 240. All other values are  
rejected.  
Step 4  
spanning-tree vlan vlan-id port-priority priority  
Configure the VLAN port priority for an interface.  
•
For vlan-id, you can specify a single VLAN identified  
by VLAN ID number, a range of VLANs separated by  
a hyphen, or a series of VLANs separated by a comma.  
Valid interfaces include physical ports, VLANs, and  
port channels. The range is 1 to 4094.  
For priority, the range is 0 to 240 in increments of 16.  
The default is 128. The lower the number, the higher  
the priority.  
Valid priority values are 0, 16, 32, 48, 64, 80, 96, 112,  
128, 144, 160, 176, 192, 208, 224, and 240. All other  
values are rejected.  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree interface interface-id  
or  
show spanning-tree vlan vlan-id  
copy running-config startup-config  
Step 7  
(Optional) Save your entries in the configuration file.  
Note  
The show spanning-tree interface interface-id privileged EXEC command displays information only  
if the port is in a link-up operative state. Otherwise, you can use the show running-config interface  
privileged EXEC command to confirm the configuration.  
To return the interface to its default setting, use the no spanning-tree [vlan vlan-id] port-priority  
interface configuration command. For information on how to configure load sharing on trunk ports by  
using spanning-tree port priorities, see the “Load Sharing Using STP” section on page 12-22.  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Configuring the Path Cost  
The spanning-tree path cost default value is derived from the media speed of an interface. If a loop  
occurs, spanning tree uses cost when selecting an interface to put in the forwarding state. You can assign  
lower cost values to interfaces that you want selected first and higher cost values that you want selected  
last. If all interfaces have the same cost value, spanning tree puts the interface with the lowest interface  
number in the forwarding state and blocks the other interfaces.  
Beginning in privileged EXEC mode, follow these steps to configure the cost of an interface. This  
procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify an interface to configure, and enter interface  
configuration mode. Valid interfaces include physical interfaces  
and port-channel logical interfaces (port-channel  
port-channel-number).  
Step 3  
Step 4  
spanning-tree cost cost  
Configure the cost for an interface.  
If a loop occurs, spanning tree uses the path cost when selecting  
an interface to place into the forwarding state. A lower path cost  
represents higher-speed transmission.  
For cost, the range is 1 to 200000000; the default value is derived  
from the media speed of the interface.  
spanning-tree vlan vlan-id cost cost  
Configure the cost for a VLAN.  
If a loop occurs, spanning tree uses the path cost when selecting  
an interface to place into the forwarding state. A lower path cost  
represents higher-speed transmission.  
•
For vlan-id, you can specify a single VLAN identified by  
VLAN ID number, a range of VLANs separated by a hyphen,  
or a series of VLANs separated by a comma. Valid interfaces  
include physical ports, VLANs, and port channels. The range  
is 1 to 4094.  
•
For cost, the range is 1 to 200000000; the default value is  
derived from the media speed of the interface.  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree interface interface-id  
or  
show spanning-tree vlan vlan-id  
copy running-config startup-config  
Step 7  
(Optional) Save your entries in the configuration file.  
Note  
The show spanning-tree interface interface-id privileged EXEC command displays information only  
for ports that are in a link-up operative state. Otherwise, you can use the show running-config privileged  
EXEC command to confirm the configuration.  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
To return the interface to its default setting, use the no spanning-tree [vlan vlan-id] cost interface  
configuration command. For information on how to configure load sharing on trunk ports by using  
spanning-tree path costs, see the “Load Sharing Using STP” section on page 12-22.  
Configuring the Switch Priority of a VLAN  
You can configure the switch priority and make it more likely that the switch will be chosen as the root  
switch.  
Note  
Exercise care when using this command. For most situations, we recommend that you use the  
spanning-tree vlan vlan-id root primary and the spanning-tree vlan vlan-id root secondary global  
configuration commands to modify the switch priority.  
Beginning in privileged EXEC mode, follow these steps to configure the switch priority of a VLAN. This  
procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree vlan vlan-id priority priority  
Configure the switch priority of a VLAN.  
•
For vlan-id, you can specify a single VLAN identified by  
VLAN ID number, a range of VLANs separated by a  
hyphen, or a series of VLANs separated by a comma.  
Valid interfaces include physical ports, VLANs, and port  
channels. The range is 1 to 4094.  
•
For priority, the range is 0 to 61440 in increments of  
4096; the default is 32768. The lower the number, the  
more likely the switch will be chosen as the root switch.  
Valid priority values are 4096, 8192, 12288, 16384,  
20480, 24576, 28672, 32768, 36864, 40960, 45056,  
49152, 53248, 57344, and 61440. All other values are  
rejected.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree vlan vlan-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree vlan vlan-id priority global  
configuration command.  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Configuring Spanning-Tree Timers  
Table 9-4 describes the timers that affect the entire spanning-tree performance.  
Table 9-4  
Spanning-Tree Timers  
Variable  
Description  
Hello timer  
Determines how often the switch broadcasts hello messages to other switches.  
Forward-delay timer  
Determines how long each of the listening and learning states last before the interface begins  
forwarding.  
Maximum-age timer  
Determines the amount of time the switch stores protocol information received on an interface.  
The sections that follow provide the configuration steps.  
Configuring the Hello Time  
You can configure the interval between the generation of configuration messages by the root switch by  
changing the hello time.  
Note  
Exercise care when using this command. For most situations, we recommend that you use the  
spanning-tree vlan vlan-id root primary and the spanning-tree vlan vlan-id root secondary global  
configuration commands to modify the hello time.  
Beginning in privileged EXEC mode, follow these steps to configure the hello time of a VLAN. This  
procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree vlan vlan-id hello-time seconds  
Configure the hello time of a VLAN. The hello time is the  
interval between the generation of configuration messages by  
the root switch. These messages mean that the switch is alive.  
•
For vlan-id, you can specify a single VLAN identified by  
VLAN ID number, a range of VLANs separated by a  
hyphen, or a series of VLANs separated by a comma.  
Valid interfaces include physical ports, VLANs, and port  
channels. The range is 1 to 4094.  
•
For seconds, the range is 1 to 10; the default is 2.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree vlan vlan-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree vlan vlan-id hello-time global  
configuration command.  
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Chapter 9 Configuring STP  
Configuring Spanning-Tree Features  
Configuring the Forwarding-Delay Time for a VLAN  
Beginning in privileged EXEC mode, follow these steps to configure the forwarding-delay time for a  
VLAN. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree vlan vlan-id forward-time  
seconds  
Configure the forward time of a VLAN. The forward delay is the  
number of seconds a port waits before changing from its  
spanning-tree learning and listening states to the forwarding state.  
•
For vlan-id, you can specify a single VLAN identified by  
VLAN ID number, a range of VLANs separated by a hyphen,  
or a series of VLANs separated by a comma. Valid interfaces  
include physical ports, VLANs, and port channels. The range  
is 1 to 4094.  
•
For seconds, the range is 4 to 30; the default is 15.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree vlan vlan-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree vlan vlan-id forward-time global  
configuration command.  
Configuring the Maximum-Aging Time for a VLAN  
Beginning in privileged EXEC mode, follow these steps to configure the maximum-aging time for a  
VLAN. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree vlan vlan-id max-age seconds  
Configure the maximum-aging time of a VLAN. The  
maximum-aging time is the number of seconds a switch waits  
without receiving spanning-tree configuration messages before  
attempting a reconfiguration.  
•
For vlan-id, you can specify a single VLAN identified by  
VLAN ID number, a range of VLANs separated by a  
hyphen, or a series of VLANs separated by a comma. Valid  
interfaces include physical ports, VLANs, and port  
channels. The range is 1 to 4094.  
•
For seconds, the range is 6 to 40; the default is 20.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree vlan vlan-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 9 Configuring STP  
Displaying the Spanning-Tree Status  
To return the switch to its default setting, use the no spanning-tree vlan vlan-id max-age global  
configuration command.  
To return to the default setting, use the no spanning-tree transmit hold-count value global  
configuration command.  
Displaying the Spanning-Tree Status  
To display the spanning-tree status, use one or more of the privileged EXEC commands in Table 9-5:  
Table 9-5  
Commands for Displaying Spanning-Tree Status  
Command  
Purpose  
show spanning-tree active  
Displays spanning-tree information on active interfaces only.  
Displays a detailed summary of interface information.  
show spanning-tree detail  
show spanning-tree interface interface-id  
show spanning-tree summary [totals]  
Displays spanning-tree information for the specified interface.  
Displays a summary of port states or displays the total lines of the STP state  
section.  
You can clear spanning-tree counters by using the clear spanning-tree [interface interface-id]  
privileged EXEC command.  
For information about other keywords for the show spanning-tree privileged EXEC command, see the  
command reference for this release.  
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Chapter 9 Configuring STP  
Displaying the Spanning-Tree Status  
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C H A P T E R  
10  
Configuring MSTP  
This chapter describes how to configure the Cisco implementation of the IEEE 802.1s Multiple STP  
(MSTP) on your Cisco Systems Intelligent Gigabit Ethernet Switch Module.  
The MSTP enables multiple VLANs to be mapped to the same spanning-tree instance, reducing the  
number of spanning-tree instances needed to support a large number of VLANs. The MSTP provides for  
multiple forwarding paths for data traffic and enables load balancing. It improves the fault tolerance of  
the network because a failure in one instance (forwarding path) does not affect other instances  
(forwarding paths). The most common initial deployment of MSTP is in the backbone and distribution  
layers of a Layer 2 switched network. This deployment provides the highly available network required  
in a service-provider environment.  
When the switch is in the MST mode, the Rapid Spanning Tree Protocol (RSTP), which is based on  
IEEE 802.1w, is automatically enabled. The RSTP provides rapid convergence of the spanning tree  
through explicit handshaking that eliminates the IEEE 802.1D forwarding delay and quickly transitions  
root ports and designated ports to the forwarding state.  
Both MSTP and RSTP improve the spanning-tree operation and maintain backward-compatibility with  
equipment that is based on the (original) IEEE 802.1D spanning tree, with existing Cisco-proprietary  
Multiple Instance STP (MISTP) and with existing Cisco per-VLAN spanning-tree plus (PVST+) and  
rapid per-VLAN spanning-tree plus (rapid PVST+). For information about PVST+ and rapid PVST+,  
see Chapter 9, “Configuring STP.” For information about other spanning-tree features such as Port Fast,  
UplinkFast, root guard, and so forth, see Chapter 11, “Configuring Optional Spanning-Tree Features.”  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
This chapter consists of these sections:  
•
•
•
•
Understanding MSTP, page 10-2  
Understanding RSTP, page 10-5  
Configuring MSTP Features, page 10-10  
Displaying the MST Configuration and Status, page 10-22  
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Chapter 10 Configuring MSTP  
Understanding MSTP  
Understanding MSTP  
MSTP, which uses RSTP for rapid convergence, enables VLANs to be grouped into a spanning-tree  
instance, with each instance having a spanning-tree topology independent of other spanning-tree  
instances. This architecture provides multiple forwarding paths for data traffic, enables load balancing,  
and reduces the number of spanning-tree instances required to support a large number of VLANs.  
These sections describe how the MSTP works:  
•
•
•
•
Multiple Spanning-Tree Regions, page 10-2  
IST, CIST, and CST, page 10-2  
Hop Count, page 10-4  
Interoperability with IEEE 802.1D STP, page 10-4  
For configuration information, see the “Configuring MSTP Features” section on page 10-10.  
Multiple Spanning-Tree Regions  
For switches to participate in multiple spanning-tree (MST) instances, you must consistently configure  
the switches with the same MST configuration information. A collection of interconnected switches that  
have the same MST configuration comprises an MST region as shown in Figure 10-1 on page 10-7.  
The MST configuration determines to which MST region each switch belongs. The configuration  
includes the name of the region, the revision number, and the MST VLAN-to-instance assignment map.  
You configure the switch for a region by using the spanning-tree mst configuration global  
configuration command, after which the switch enters the MST configuration mode. From this mode,  
you can map VLANs to an MST instance by using the instance MST configuration command, specify  
the region name by using the name MST configuration command, and set the revision number by using  
the revision MST configuration command.  
A region can have one or multiple members with the same MST configuration; each member must be  
capable of processing RSTP bridge protocol data units (BPDUs). There is no limit to the number of MST  
regions in a network, but each region can only support up to spanning-tree instances. Instances can be  
identified by any number in the range from 0 toYou can assign a VLAN to only one spanning-tree  
instance at a time.  
IST, CIST, and CST  
Unlike PVST+ and rapid PVST+ in which all the spanning-tree instances are independent, the MSTP  
establishes and maintains two types of spanning trees:  
•
An internal spanning tree (IST), which is the spanning tree that runs in an MST region.  
Within each MST region, the MSTP maintains multiple spanning-tree instances. Instance 0 is a  
special instance for a region, known as the internal spanning tree (IST). All other MST instances are  
numbered from 1 to .  
The IST is the only spanning-tree instance that sends and receives BPDUs. All of the other  
spanning-tree instance information is contained in M-records, which are encapsulated within MSTP  
BPDUs. Because the MSTP BPDU carries information for all instances, the number of BPDUs that  
need to be processed to support multiple spanning-tree instances is significantly reduced.  
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Chapter 10 Configuring MSTP  
Understanding MSTP  
All MST instances within the same region share the same protocol timers, but each MST instance  
has its own topology parameters, such as root switch ID, root path cost, and so forth. By default, all  
VLANs are assigned to the IST.  
An MST instance is local to the region; for example, MST instance 1 in region A is independent of  
MST instance 1 in region B, even if regions A and B are interconnected.  
•
A common and internal spanning tree (CIST), which is a collection of the ISTs in each MST region,  
and the common spanning tree (CST) that interconnects the MST regions and single spanning trees.  
The spanning tree computed in a region appears as a subtree in the CST that encompasses the entire  
switched domain. The CIST is formed by the spanning-tree algorithm among switches that support  
the IEEE 802.1w, IEEE 802.1s, and IEEE 802.1D standards. The CIST inside an MST region is the  
same as the CST outside a region.  
For more information, see the “Operations Within an MST Region” section on page 10-3 and the .  
Operations Within an MST Region  
The IST connects all the MSTP switches in a region. When the IST converges, the root of the IST  
becomes the IST master. It is the switch within the region with the lowest switch ID and path cost to  
the CST root. The IST master also is the CST root if there is only one region in the network. If the CST  
root is outside the region, one of the MSTP switches at the boundary of the region is selected as the IST  
master.  
When an MSTP switch initializes, it sends BPDUs claiming itself as the root of the CST and the IST  
master, with both of the path costs to the CST root and to the IST master set to zero. The switch also  
initializes all of its MST instances and claims to be the root for all of them. If the switch receives superior  
MST root information (lower switch ID, lower path cost, and so forth) than stored for the switch, it  
relinquishes its claim as the IST master.  
During initialization, a region might have many subregions, each with its own IST master. As switches  
receive superior IST information, they leave their old subregions and join the new subregion that  
contains the true IST master. Thus all subregions shrink, except for the one that contains the true IST  
master.  
For correct operation, all switches in the MST region must agree on the same IST master. Therefore, any  
two switches in the region synchronize their port roles for an MST instance only if they converge to a  
common IST master.  
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Understanding MSTP  
Hop Count  
IST master  
and CST root  
A
D
Legacy 802.1D  
MST Region 1  
B
C
IST master  
IST master  
MST Region 2  
MST Region 3  
The IST and MST instances do not use the message-age and maximum-age information in the  
configuration BPDU to compute the spanning-tree topology. Instead, they use the path cost to the root  
and a hop-count mechanism similar to the IP time-to-live (TTL) mechanism.  
By using the spanning-tree mst max-hops global configuration command, you can configure the  
maximum hops inside the region and apply it to the IST and all MST instances in that region. The hop  
count achieves the same result as the message-age information (determines when to trigger a  
reconfiguration). The root switch of the instance always sends a BPDU (or M-record) with a cost of 0  
and the hop count set to the maximum value. When a switch receives this BPDU, it decrements the  
received remaining hop count by one and propagates this value as the remaining hop count in the BPDUs  
it generates. When the count reaches zero, the switch discards the BPDU and ages the information held  
for the port.  
The message-age and maximum-age information in the RSTP portion of the BPDU remain the same  
throughout the region, and the same values are propagated by the region designated ports at the  
boundary.  
Interoperability with IEEE 802.1D STP  
A switch running MSTP supports a built-in protocol migration mechanism that enables it to interoperate  
with legacy IEEE 802.1D switches. If this switch receives a legacy IEEE 802.1D configuration BPDU  
(a BPDU with the protocol version set to 0), it sends only IEEE 802.1D BPDUs on that port. An MSTP  
switch can also detect that a port is at the boundary of a region when it receives a legacy BPDU, an  
MSTP BPDU (version 3) associated with a different region, or an RSTP BPDU (version 2).  
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Chapter 10 Configuring MSTP  
Understanding RSTP  
However, the switch does not automatically revert to the MSTP mode if it no longer receives IEEE  
802.1D BPDUs because it cannot determine whether the legacy switch has been removed from the link  
unless the legacy switch is the designated switch. A switch might also continue to assign a boundary role  
to a port when the switch to which this switch is connected has joined the region. To restart the protocol  
migration process (force the renegotiation with neighboring switches), use the clear spanning-tree  
detected-protocols privileged EXEC command.  
If all the legacy switches on the link are RSTP switches, they can process MSTP BPDUs as if they are  
RSTP BPDUs. Therefore, MSTP switches send either a version 0 configuration and TCN BPDUs or  
version 3 MSTP BPDUs on a boundary port. A boundary port connects to a LAN, the designated switch  
of which is either a single spanning-tree switch or a switch with a different MST configuration.  
Understanding RSTP  
The RSTP takes advantage of point-to-point wiring and provides rapid convergence of the spanning tree.  
Reconfiguration of the spanning tree can occur in less than 1 second (in contrast to 50 seconds with the  
default settings in the IEEE 802.1D spanning tree).  
These section describes how the RSTP works:  
•
•
•
•
Port Roles and the Active Topology, page 10-5  
Rapid Convergence, page 10-6  
Synchronization of Port Roles, page 10-7  
Bridge Protocol Data Unit Format and Processing, page 10-8  
For configuration information, see the “Configuring MSTP Features” section on page 10-10.  
Port Roles and the Active Topology  
The RSTP provides rapid convergence of the spanning tree by assigning port roles and by determining  
the active topology. The RSTP builds upon the IEEE 802.1D STP to select the switch with the highest  
switch priority (lowest numerical priority value) as the root switch as described in the “Spanning-Tree  
Topology and BPDUs” section on page 9-3. Then the RSTP assigns one of these port roles to individual  
ports:  
•
•
Root port—Provides the best path (lowest cost) when the switch forwards packets to the root switch.  
Designated port—Connects to the designated switch, which incurs the lowest path cost when  
forwarding packets from that LAN to the root switch. The port through which the designated switch  
is attached to the LAN is called the designated port.  
•
•
Alternate port—Offers an alternate path toward the root switch to that provided by the current root  
port.  
Backup port—Acts as a backup for the path provided by a designated port toward the leaves of the  
spanning tree. A backup port can exist only when two ports are connected in a loopback by a  
point-to-point link or when a switch has two or more connections to a shared LAN segment.  
•
Disabled port—Has no role within the operation of the spanning tree.  
A port with the root or a designated port role is included in the active topology. A port with the alternate or  
backup port role is excluded from the active topology.  
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Chapter 10 Configuring MSTP  
Understanding RSTP  
In a stable topology with consistent port roles throughout the network, the RSTP ensures that every root  
port and designated port immediately transition to the forwarding state while all alternate and backup  
ports are always in the discarding state (equivalent to blocking in IEEE 802.1D). The port state controls  
the operation of the forwarding and learning processes. Table 10-1 provides a comparison of IEEE  
802.1D and RSTP port states.  
Table 10-1  
Port State Comparison  
STP Port State  
(IEEE 802.1D)  
Is Port Included in the  
Active Topology?  
Operational Status  
Enabled  
RSTP Port State  
Discarding  
Discarding  
Learning  
Blocking  
No  
No  
Yes  
Yes  
No  
Enabled  
Listening  
Learning  
Enabled  
Enabled  
Forwarding  
Disabled  
Forwarding  
Discarding  
Disabled  
To be consistent with Cisco STP implementations, this guide defines the port state as blocking instead  
of discarding. Designated ports start in the listening state.  
Rapid Convergence  
The RSTP provides for rapid recovery of connectivity following the failure of a switch, a switch port,  
or a LAN. It provides rapid convergence for edge ports, new root ports, and ports connected through  
point-to-point links as follows:  
•
Edge ports—If you configure a port as an edge port on an RSTP switch by using the spanning-tree  
portfast interface configuration command, the edge port immediately transitions to the forwarding  
state. An edge port is the same as a Port Fast-enabled port, and you should enable it only on ports  
that connect to a single end station.  
•
•
Root ports—If the RSTP selects a new root port, it blocks the old root port and immediately  
transitions the new root port to the forwarding state.  
Point-to-point links—If you connect a port to another port through a point-to-point link and the local  
port becomes a designated port, it negotiates a rapid transition with the other port by using the  
proposal-agreement handshake to ensure a loop-free topology.  
As shown in Figure 10-1, Switch A is connected to Switch B through a point-to-point link, and all  
of the ports are in the blocking state. Assume that the priority of Switch A is a smaller numerical  
value than the priority of Switch B. Switch A sends a proposal message (a configuration BPDU)  
with the proposal flag set) to Switch B, proposing itself as the designated switch.  
After receiving the proposal message, Switch B selects as its new root port the port from which the  
proposal message was received, forces all nonedge ports to the blocking state, and sends an  
agreement message (a BPDU with the agreement flag set) through its new root port.  
After receiving Switch B’s agreement message, Switch A also immediately transitions its  
designated port to the forwarding state. No loops in the network are formed because Switch B  
blocked all of its nonedge ports and because there is a point-to-point link between Switches A and B.  
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Chapter 10 Configuring MSTP  
Understanding RSTP  
When Switch C is connected to Switch B, a similar set of handshaking messages are exchanged.  
Switch C selects the port connected to Switch B as its root port, and both ends immediately  
transition to the forwarding state. With each iteration of this handshaking process, one more switch  
joins the active topology. As the network converges, this proposal-agreement handshaking  
progresses from the root toward the leaves of the spanning tree.  
The switch determines the link type from the port duplex mode: a full-duplex port is considered to  
have a point-to-point connection; a half-duplex port is considered to have a shared connection. You  
can override the default setting that is determined by the duplex setting by using the spanning-tree  
link-type interface configuration command.  
Figure 10-1  
Switch A  
Proposal and Agreement Handshaking for Rapid Convergence  
Switch B  
Proposal  
Designated  
Root  
Root  
Root  
switch  
Agreement  
F
F
DP  
RP  
Designated  
switch  
Switch C  
Proposal  
F
F
DP  
RP  
Designated  
switch  
Agreement  
F
F
F
F
DP  
RP  
DP  
RP  
DP = designated port  
RP = root port  
F = forwarding  
Synchronization of Port Roles  
When the switch receives a proposal message on one of its ports and that port is selected as the new root  
port, the RSTP forces all other ports to synchronize with the new root information.  
The switch is synchronized with superior root information received on the root port if all other ports are  
synchronized. An individual port on the switch is synchronized if  
•
•
That port is in the blocking state  
It is an edge port (a port configured to be at the edge of the network)  
If a designated port is in the forwarding state and is not configured as an edge port, it transitions to the  
blocking state when the RSTP forces it to synchronize with new root information. In general, when the  
RSTP forces a port to synchronize with root information and the port does not satisfy any of the above  
conditions, its port state is set to blocking.  
After ensuring that all of the ports are synchronized, the switch sends an agreement message to the designated  
switch corresponding to its root port. When the switches connected by a point-to-point link are in agreement  
about their port roles, the RSTP immediately transitions the port states to forwarding. The sequence of events  
is shown in Figure 10-2.  
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Chapter 10 Configuring MSTP  
Understanding RSTP  
Figure 10-2  
Sequence of Events During Rapid Convergence  
4. Agreement  
5. Forward  
1. Proposal  
Edge port  
2. Block  
9. Forward  
3. Block  
11. Forward  
8. Agreement  
6. Proposal  
7. Proposal  
10. Agreement  
Root port  
Designated port  
Bridge Protocol Data Unit Format and Processing  
The RSTP BPDU format is the same as the IEEE 802.1D BPDU format except that the protocol version  
is set to 2. A new 1-byte version 1 Length field is set to zero, which means that no version 1 protocol  
information is present. Table 10-2 shows the RSTP flag fields.  
Table 10-2  
RSTP BPDU Flags  
Bit  
0
Function  
Topology change (TC)  
1
Proposal  
Port role:  
2–3:  
00  
01  
10  
11  
4
Unknown  
Alternate port  
Root port  
Designated port  
Learning  
5
Forwarding  
6
Agreement  
7
Topology change acknowledgement (TCA)  
The sending switch sets the proposal flag in the RSTP BPDU to propose itself as the designated switch  
on that LAN. The port role in the proposal message is always set to the designated port.  
The sending switch sets the agreement flag in the RSTP BPDU to accept the previous proposal. The port  
role in the agreement message is always set to the root port.  
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Chapter 10 Configuring MSTP  
Understanding RSTP  
The RSTP does not have a separate topology change notification (TCN) BPDU. It uses the topology  
change (TC) flag to show the topology changes. However, for interoperability with IEEE 802.1D  
switches, the RSTP switch processes and generates TCN BPDUs.  
The learning and forwarding flags are set according to the state of the sending port.  
Processing Superior BPDU Information  
If a port receives superior root information (lower switch ID, lower path cost, and so forth) than currently  
stored for the port, the RSTP triggers a reconfiguration. If the port is proposed and is selected as the new  
root port, RSTP forces all the other ports to synchronize.  
If the BPDU received is an RSTP BPDU with the proposal flag set, the switch sends an agreement  
message after all of the other ports are synchronized. If the BPDU is an IEEE 802.1D BPDU, the switch  
does not set the proposal flag and starts the forward-delay timer for the port. The new root port requires  
twice the forward-delay time to transition to the forwarding state.  
If the superior information received on the port causes the port to become a backup or alternate port,  
RSTP sets the port to the blocking state but does not send the agreement message. The designated port  
continues sending BPDUs with the proposal flag set until the forward-delay timer expires, at which time  
the port transitions to the forwarding state.  
Processing Inferior BPDU Information  
If a designated port receives an inferior BPDU (higher switch ID, higher path cost, and so forth than  
currently stored for the port) with a designated port role, it immediately replies with its own information.  
Topology Changes  
This section describes the differences between the RSTP and the IEEE 802.1D in handling spanning-tree  
topology changes.  
•
Detection—Unlike IEEE 802.1D in which any transition between the blocking and the forwarding  
state causes a topology change, only transitions from the blocking to the forwarding state cause a  
topology change with RSTP (only an increase in connectivity is considered a topology change).  
State changes on an edge port do not cause a topology change. When an RSTP switch detects a  
topology change, it deletes the learned information on all of its nonedge ports except on those from  
which it received the TC notification.  
•
•
Notification—Unlike IEEE 802.1D, which uses TCN BPDUs, the RSTP does not use them.  
However, for IEEE 802.1D interoperability, an RSTP switch processes and generates TCN BPDUs.  
Acknowledgement—When an RSTP switch receives a TCN message on a designated port from an  
IEEE 802.1D switch, it replies with an IEEE 802.1D configuration BPDU with the TCA bit set.  
However, if the TC-while timer (the same as the topology-change timer in IEEE 802.1D) is active  
on a root port connected to an IEEE 802.1D switch and a configuration BPDU with the TCA bit set  
is received, the TC-while timer is reset.  
This behavior is only required to support IEEE 802.1D switches. The RSTP BPDUs never have the  
TCA bit set.  
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Configuring MSTP Features  
•
Propagation—When an RSTP switch receives a TC message from another switch through a  
designated or root port, it propagates the change to all of its nonedge, designated ports and to the  
root port (excluding the port on which it is received). The switch starts the TC-while timer for all  
such ports and flushes the information learned on them.  
•
Protocol migration—For backward compatibility with IEEE 802.1D switches, RSTP selectively  
sends IEEE 802.1D configuration BPDUs and TCN BPDUs on a per-port basis.  
When a port is initialized, the migrate-delay timer is started (specifies the minimum time during  
which RSTP BPDUs are sent), and RSTP BPDUs are sent. While this timer is active, the switch  
processes all BPDUs received on that port and ignores the protocol type.  
If the switch receives an IEEE 802.1D BPDU after the port migration-delay timer has expired, it  
assumes that it is connected to an IEEE 802.1D switch and starts using only IEEE 802.1D BPDUs.  
However, if the RSTP switch is using IEEE 802.1D BPDUs on a port and receives an RSTP BPDU  
after the timer has expired, it restarts the timer and starts using RSTP BPDUs on that port.  
Configuring MSTP Features  
These sections describe how to configure basic MSTP features:  
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Default MSTP Configuration, page 10-11  
MSTP Configuration Guidelines, page 10-11  
Specifying the MST Region Configuration and Enabling MSTP, page 10-12 (required)  
Configuring the Root Switch, page 10-13 (optional)  
Configuring a Secondary Root Switch, page 10-15 (optional)  
Configuring the Port Priority, page 10-15 (optional)  
Configuring the Path Cost, page 10-17 (optional)  
Configuring the Switch Priority, page 10-18 (optional)  
Configuring the Hello Time, page 10-18 (optional)  
Configuring the Forwarding-Delay Time, page 10-19 (optional)  
Configuring the Maximum-Aging Time, page 10-20 (optional)  
Configuring the Maximum-Hop Count, page 10-20 (optional)  
Specifying the Link Type to Ensure Rapid Transitions, page 10-21 (optional)  
Restarting the Protocol Migration Process, page 10-21 (optional)  
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Chapter 10 Configuring MSTP  
Configuring MSTP Features  
Default MSTP Configuration  
Table 10-3 shows the default MSTP configuration.  
Table 10-3 Default MSTP Configuration  
Feature  
Default Setting  
Spanning-tree mode  
PVST+ (Rapid PVST+ and MSTP are disabled).  
32768.  
Switch priority (configurable on a per-CIST interface basis)  
Spanning-tree port priority (configurable on a per-CIST interface basis) 128.  
Spanning-tree port cost (configurable on a per-CIST interface basis)  
1000 Mbps: 4.  
100 Mbps: 100 (for the internal 100 Mbps  
management module ports).  
100 Mbps: 19 (for the external ports).  
10 Mbps: 100.  
2 seconds.  
Hello time  
Forward-delay time  
Maximum-aging time  
Maximum hop count  
15 seconds.  
20 seconds.  
20 hops.  
For information about the supported number of spanning-tree instances, see the “Supported  
Spanning-Tree Instances” section on page 9-9.  
MSTP Configuration Guidelines  
These are the configuration guidelines for MSTP:  
•
•
•
•
When you enable MST by using the spanning-tree mode mst global configuration command, RSTP  
is automatically enabled.  
For two or more switches to be in the same MST region, they must have the same VLAN-to-instance  
map, the same configuration revision number, and the same name.  
The switch supports up to 16 MST instances. The number of VLANs that can be mapped to a  
particular MST instance is unlimited.  
PVST+, rapid PVST+, and MSTP are supported, but only one version can be active at any time. (For  
example, all VLANs run PVST+, all VLANs run rapid PVST+, or all VLANs run MSTP.) For more  
information, see the “Spanning-Tree Interoperability and Backward Compatibility” section on  
page 9-10.  
•
•
VTP propagation of the MST configuration is not supported. However, you can manually configure  
the MST configuration (region name, revision number, and VLAN-to-instance mapping) on each  
switch within the MST region by using the command-line interface (CLI) or through the SNMP  
support.  
For load balancing across redundant paths in the network to work, all VLAN-to-instance mapping  
assignments must match; otherwise, all traffic flows on a single link.  
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Configuring MSTP Features  
•
All MST boundary ports must be forwarding for load balancing between a PVST+ and an MST  
cloud or between a rapid-PVST+ and an MST cloud. For this to occur, the IST master of the MST  
cloud should also be the root of the CST. If the MST cloud consists of multiple MST regions, one  
of the MST regions must contain the CST root, and all of the other MST regions must have a better  
path to the root contained within the MST cloud than a path through the PVST+ or rapid-PVST+  
cloud. You might have to manually configure the switches in the clouds.  
•
•
Partitioning the network into a large number of regions is not recommended. However, if this  
situation is unavoidable, we recommend that you partition the switched LAN into smaller LANs  
interconnected by routers or non-Layer 2 devices.  
For configuration guidelines about UplinkFast and BackboneFast, see the “Optional Spanning-Tree  
Configuration Guidelines” section on page 11-10.  
Specifying the MST Region Configuration and Enabling MSTP  
For two or more switches to be in the same MST region, they must have the same VLAN-to-instance  
mapping, the same configuration revision number, and the same name.  
A region can have one member or multiple members with the same MST configuration; each member  
must be capable of processing RSTP BPDUs. There is no limit to the number of MST regions in a  
network, but each region can only support up to spanning-tree instances. You can assign a VLAN to  
only one spanning-tree instance at a time.  
Beginning in privileged EXEC mode, follow these steps to specify the MST region configuration and  
enable MSTP. This procedure is required.  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
Enter global configuration mode.  
Enter MST configuration mode.  
Map VLANs to an MST instance.  
spanning-tree mst configuration  
instance instance-id vlan vlan-range  
•
For instance-id, you can specify a single instance, a range of  
instances separated by a hyphen, or a series of instances separated by  
a comma. The range is 1 to .  
•
For vlan vlan-range, the range is 1 to 4094.  
When you map VLANs to an MST instance, the mapping is incremental,  
and the VLANs specified in the command are added to or removed from  
the VLANs that were previously mapped.  
To specify a VLAN range, use a hyphen; for example, instance 1 vlan  
1-63 maps VLANs 1 through 63 to MST instance 1.  
To specify a VLAN series, use a comma; for example, instance 1 vlan  
10, 20, 30 maps VLANs 10, 20, and 30 to MST instance 1.  
Step 4  
name name  
Specify the configuration name. The name string has a maximum length  
of 32 characters and is case sensitive.  
Step 5  
Step 6  
Step 7  
revision version  
show pending  
exit  
Specify the configuration revision number. The range is 0 to 65535.  
Verify your configuration by displaying the pending configuration.  
Apply all changes, and return to global configuration mode.  
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Configuring MSTP Features  
Command  
Purpose  
Step 8  
spanning-tree mode mst  
Enable MSTP. RSTP is also enabled.  
Caution  
Changing spanning-tree modes can disrupt traffic because all  
spanning-tree instances are stopped for the previous mode and  
restarted in the new mode.  
You cannot run both MSTP and PVST+ or both MSTP and rapid PVST+  
at the same time.  
Step 9  
end  
Return to privileged EXEC mode.  
Verify your entries.  
Step 10  
Step 11  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return to the default MST region configuration, use the no spanning-tree mst configuration global  
configuration command. To return to the default VLAN-to-instance map, use the no instance  
instance-id [vlan vlan-range] MST configuration command. To return to the default name, use the no  
name MST configuration command. To return to the default revision number, use the no revision MST  
configuration command. To re-enable PVST+, use the no spanning-tree mode or the spanning-tree  
mode pvst global configuration command.  
This example shows how to enter MST configuration mode, map VLANs 10 to 20 to MST instance 1,  
name the region region1, set the configuration revision to 1, display the pending configuration, apply  
the changes, and return to global configuration mode:  
Switch(config)# spanning-tree mst configuration  
Switch(config-mst)# instance 1 vlan 10-20  
Switch(config-mst)# name region1  
Switch(config-mst)# revision 1  
Switch(config-mst)# show pending  
Pending MST configuration  
Name  
[region1]  
Revision 1  
Instance Vlans Mapped  
-------- ---------------------  
0
1
1-9,21-4094  
10-20  
-------------------------------  
Switch(config-mst)# exit  
Switch(config)#  
Configuring the Root Switch  
The switch maintains a spanning-tree instance for the group of VLANs mapped to it. A switch ID,  
consisting of the switch priority and the switch MAC address, is associated with each instance. The  
switch with the lowest switch ID becomes the root switch for the group of VLANs.  
To configure a switch to become the root, use the spanning-tree mst instance-id root global  
configuration command to modify the switch priority from the default value (32768) to a significantly  
lower value so that the switch becomes the root switch for the specified spanning-tree instance. When  
you enter this command, the switch checks the switch priorities of the root switches. Because of the  
extended system ID support, the switch sets its own priority for the specified instance to 24576 if this  
value will cause this switch to become the root for the specified spanning-tree instance.  
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Configuring MSTP Features  
If any root switch for the specified instance has a switch priority lower than 24576, the switch sets its  
own priority to 4096 less than the lowest switch priority. (4096 is the value of the least-significant bit  
of a 4-bit switch priority value as shown in Table 9-1 on page 9-4.)  
If your network consists of switches that both do and do not support the extended system ID, it is  
unlikely that the switch with the extended system ID support will become the root switch. The extended  
system ID increases the switch priority value every time the VLAN number is greater than the priority  
of the connected switches running older software.  
The root switch for each spanning-tree instance should be a backbone or distribution switch. Do not  
configure an access switch as the spanning-tree primary root.  
Use the diameter keyword, which is available only for MST instance 0, to specify the Layer 2 network  
diameter (that is, the maximum number of switch hops between any two end stations in the Layer 2  
network). When you specify the network diameter, the switch automatically sets an optimal hello time,  
forward-delay time, and maximum-age time for a network of that diameter, which can significantly  
reduce the convergence time. You can use the hello keyword to override the automatically calculated  
hello time.  
Note  
After configuring the switch as the root switch, we recommend that you avoid manually configuring the  
hello time, forward-delay time, and maximum-age time by using the spanning-tree mst hello-time,  
spanning-tree mst forward-time, and the spanning-tree mst max-age global configuration commands  
after configuring the switch as the root switch.  
Beginning in privileged EXEC mode, follow these steps to configure a switch as the root switch. This  
procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree mst instance-id root primary  
[diameter net-diameter [hello-time seconds]]  
Configure a switch as the root switch.  
•
For instance-id, you can specify a single instance, a range  
of instances separated by a hyphen, or a series of instances  
separated by a comma. The range is 0 to .  
•
(Optional) For diameter net-diameter, specify the  
maximum number of switches between any two end  
stations. The range is 2 to 7. This keyword is available  
only for MST instance 0.  
•
(Optional) For hello-time seconds, specify the interval in  
seconds between the generation of configuration messages  
by the root switch. The range is 1 to 10 seconds; the  
default is 2 seconds.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree mst instance-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree mst instance-id root global  
configuration command.  
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Chapter 10 Configuring MSTP  
Configuring MSTP Features  
Configuring a Secondary Root Switch  
When you configure a switch that supports the extended system ID as the secondary root, the  
spanning-tree switch priority is modified from the default value (32768) to 28672. The switch is then  
likely to become the root switch for the specified instance if the primary root switch fails. This is  
assuming that the other network switches use the default switch priority of 32768 and therefore are  
unlikely to become the root switch.  
You can execute this command on more than one switch to configure multiple backup root switches. Use  
the same network diameter and hello-time values that you used when you configured the primary root  
switch with the spanning-tree mst instance-id root primary global configuration command.  
Beginning in privileged EXEC mode, follow these steps to configure a switch as the secondary root  
switch. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree mst instance-id root  
secondary [diameter net-diameter  
[hello-time seconds]]  
Configure a switch as the secondary root switch.  
•
•
•
For instance-id, you can specify a single instance, a range of  
instances separated by a hyphen, or a series of instances  
separated by a comma. The range is 0 to .  
(Optional) For diameter net-diameter, specify the maximum  
number of switches between any two end stations. The range is 2  
to 7. This keyword is available only for MST instance 0.  
(Optional) For hello-time seconds, specify the interval in  
seconds between the generation of configuration messages by  
the root switch. The range is 1 to 10 seconds; the default  
is 2 seconds.  
Use the same network diameter and hello-time values that you used  
when configuring the primary root switch. See the “Configuring the  
Root Switch” section on page 10-13.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree mst instance-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree mst instance-id root global  
configuration command.  
Configuring the Port Priority  
If a loop occurs, the MSTP uses the port priority when selecting an interface to put into the forwarding  
state. You can assign higher priority values (lower numerical values) to interfaces that you want selected  
first and lower priority values (higher numerical values) that you want selected last. If all interfaces have  
the same priority value, the MSTP puts the interface with the lowest interface number in the forwarding  
state and blocks the other interfaces.  
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Chapter 10 Configuring MSTP  
Configuring MSTP Features  
Beginning in privileged EXEC mode, follow these steps to configure the MSTP port priority of an  
interface. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify an interface to configure, and enter interface  
configuration mode.  
Valid interfaces include physical ports and port channels.  
Valid port-channel numbers are 1 to 6.  
Step 3  
spanning-tree mst instance-id port-priority priority Configure the port priority for an MST instance.  
•
For instance-id, you can specify a single instance, a  
range of instances separated by a hyphen, or a series of  
instances separated by a comma. The range is 0 to .  
•
For priority, the range is 0 to 240 in increments of 16.  
The default is 128. The lower the number, the higher  
the priority.  
Valid priority values are 0, 16, 32, 48, 64, 80, 96, 112,  
128, 144, 160, 176, 192, 208, 224, and 240. All other  
values are rejected.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree mst interface interface-id  
or  
show spanning-tree mst instance-id  
copy running-config startup-config  
Step 6  
(Optional) Save your entries in the configuration file.  
Note  
The show spanning-tree mst interface interface-id privileged EXEC command displays information  
only if the port is in a link-up operative state. Otherwise, you can use the show running-config interface  
privileged EXEC command to confirm the configuration.  
To return the interface to its default setting, use the no spanning-tree mst instance-id port-priority  
interface configuration command.  
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Chapter 10 Configuring MSTP  
Configuring MSTP Features  
Configuring the Path Cost  
The MSTP path cost default value is derived from the media speed of an interface. If a loop occurs, the  
MSTP uses cost when selecting an interface to put in the forwarding state. You can assign lower cost  
values to interfaces that you want selected first and higher cost values that you want selected last. If all  
interfaces have the same cost value, the MSTP puts the interface with the lowest interface number in the  
forwarding state and blocks the other interfaces.  
Beginning in privileged EXEC mode, follow these steps to configure the MSTP cost of an interface. This  
procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify an interface to configure, and enter interface  
configuration mode. Valid interfaces include physical ports and  
port channels. Valid port-channel numbers are 1 to 6.  
Step 3  
spanning-tree mst instance-id cost cost  
Configure the cost for an MST instance.  
If a loop occurs, the MSTP uses the path cost when selecting an  
interface to place into the forwarding state. A lower path cost  
represents higher-speed transmission.  
•
For instance-id, you can specify a single instance, a range of  
instances separated by a hyphen, or a series of instances  
separated by a comma. The range is 0 to .  
•
For cost, the range is 1 to 200000000; the default value is  
derived from the media speed of the interface.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
show spanning-tree mst interface interface-id Verify your entries.  
or  
show spanning-tree mst instance-id  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Note  
The show spanning-tree mst interface interface-id privileged EXEC command displays information  
only for ports that are in a link-up operative state. Otherwise, you can use the show running-config  
privileged EXEC command to confirm the configuration.  
To return the interface to its default setting, use the no spanning-tree mst instance-id cost interface  
configuration command.  
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Chapter 10 Configuring MSTP  
Configuring MSTP Features  
Configuring the Switch Priority  
You can configure the switch priority and make it more likely that the switch will be chosen as the root  
switch.  
Note  
Exercise care when using this command. For most situations, we recommend that you use the  
spanning-tree mst instance-id root primary and the spanning-tree mst instance-id root secondary  
global configuration commands to modify the switch priority.  
Beginning in privileged EXEC mode, follow these steps to configure the switch priority. This procedure  
is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree mst instance-id priority priority  
Configure the switch priority for an MST instance.  
•
For instance-id, you can specify a single instance, a  
range of instances separated by a hyphen, or a series of  
instances separated by a comma. The range is 0 to .  
•
For priority, the range is 0 to 61440 in increments of  
4096; the default is 32768. The lower the number, the  
more likely the switch will be chosen as the root switch.  
Valid priority values are 0, 4096, 8192, 12288, 16384,  
20480, 24576, 28672, 32768, 36864, 40960, 45056,  
49152, 53248, 57344, and 61440. All other values are  
rejected.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree mst instance-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree mst instance-id priority global  
configuration command.  
Configuring the Hello Time  
You can configure the interval between the generation of configuration messages by the root switch by  
changing the hello time.  
Note  
Exercise care when using this command. For most situations, we recommend that you use the  
spanning-tree mst instance-id root primary and the spanning-tree mst instance-id root secondary  
global configuration commands to modify the hello time.  
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Chapter 10 Configuring MSTP  
Configuring MSTP Features  
Beginning in privileged EXEC mode, follow these steps to configure the hello time for all MST  
instances. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree mst hello-time seconds  
Configure the hello time for all MST instances. The hello time  
is the interval between the generation of configuration  
messages by the root switch. These messages mean that the  
switch is alive.  
For seconds, the range is 1 to 10; the default is 2.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
Step 5  
end  
show spanning-tree mst  
copy running-config startup-config  
Verify your entries.  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree mst hello-time global configuration  
command.  
Configuring the Forwarding-Delay Time  
Beginning in privileged EXEC mode, follow these steps to configure the forwarding-delay time for all  
MST instances. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree mst forward-time seconds  
Configure the forward time for all MST instances. The forward  
delay is the number of seconds a port waits before changing from  
its spanning-tree learning and listening states to the forwarding  
state.  
For seconds, the range is 4 to 30; the default is 15.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
Step 5  
end  
show spanning-tree mst  
copy running-config startup-config  
Verify your entries.  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree mst forward-time global  
configuration command.  
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Chapter 10 Configuring MSTP  
Configuring MSTP Features  
Configuring the Maximum-Aging Time  
Beginning in privileged EXEC mode, follow these steps to configure the maximum-aging time for all  
MST instances. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree mst max-age seconds  
Configure the maximum-aging time for all MST instances. The  
maximum-aging time is the number of seconds a switch waits  
without receiving spanning-tree configuration messages before  
attempting a reconfiguration.  
For seconds, the range is 6 to 40; the default is 20.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
Step 5  
end  
show spanning-tree mst  
copy running-config startup-config  
Verify your entries.  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree mst max-age global configuration  
command.  
Configuring the Maximum-Hop Count  
Beginning in privileged EXEC mode, follow these steps to configure the maximum-hop count for all  
MST instances. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree mst max-hops hop-count  
Specify the number of hops in a region before the BPDU is  
discarded, and the information held for a port is aged.  
For hop-count, the range is 1 to ; the default is 20.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
Step 5  
end  
show spanning-tree mst  
copy running-config startup-config  
Verify your entries.  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree mst max-hops global configuration  
command.  
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Chapter 10 Configuring MSTP  
Configuring MSTP Features  
Specifying the Link Type to Ensure Rapid Transitions  
If you connect a port to another port through a point-to-point link and the local port becomes a  
designated port, the RSTP negotiates a rapid transition with the other port by using the  
proposal-agreement handshake to ensure a loop-free topology as described in the “Rapid Convergence”  
section on page 10-6.  
By default, the link type is determined from the duplex mode of the interface: a full-duplex port is  
considered to have a point-to-point connection; a half-duplex port is considered to have a shared  
connection. If you have a half-duplex link physically connected point-to-point to a single port on a  
remote switch running MSTP, you can override the default setting of the link type and enable rapid  
transitions to the forwarding state.  
Beginning in privileged EXEC mode, follow these steps to override the default link-type setting. This  
procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to configure, and enter interface  
configuration mode. Valid interfaces include physical ports,  
VLANs, and port channels. Valid VLAN IDs are 1 to 4094.  
Valid port-channel numbers are 1 to 6.  
Step 3  
Step 4  
Step 5  
Step 6  
spanning-tree link-type point-to-point  
end  
Specify that the link type of a port is point-to-point.  
Return to privileged EXEC mode.  
show spanning-tree mst interface interface-id  
copy running-config startup-config  
Verify your entries.  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no spanning-tree link-type interface configuration  
command.  
Restarting the Protocol Migration Process  
A switch running MSTP supports a built-in protocol migration mechanism that enables it to interoperate  
with legacy IEEE 802.1D switches. If this switch receives a legacy IEEE 802.1D configuration BPDU  
(a BPDU with the protocol version set to 0), it sends only IEEE 802.1D BPDUs on that port. An MSTP  
switch can also detect that a port is at the boundary of a region when it receives a legacy BPDU, an MST  
BPDU (version 3) associated with a different region, or an RST BPDU (version 2).  
However, the switch does not automatically revert to the MSTP mode if it no longer receives IEEE  
802.1D BPDUs because it cannot determine whether the legacy switch has been removed from the link  
unless the legacy switch is the designated switch. A switch also might continue to assign a boundary role  
to a port when the switch to which it is connected has joined the region.  
To restart the protocol migration process (force the renegotiation with neighboring switches) on the  
switch, use the clear spanning-tree detected-protocols privileged EXEC command.  
To restart the protocol migration process on a specific interface, use the clear spanning-tree  
detected-protocols interface interface-id privileged EXEC command.  
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Chapter 10 Configuring MSTP  
Displaying the MST Configuration and Status  
Displaying the MST Configuration and Status  
To display the spanning-tree status, use one or more of the privileged EXEC commands in :  
Table 10-4  
Commands for Displaying MST Status  
Command  
Purpose  
show spanning-tree mst configuration  
show spanning-tree mst instance-id  
Displays the MST region configuration.  
Displays MST information for the specified instance.  
show spanning-tree mst interface interface-id Displays MST information for the specified interface. Valid interfaces  
include physical ports, VLANs, and port channels. Valid VLAN IDs are 1  
to 4094. The valid port-channel range is 1 to 6.  
For information about other keywords for the show spanning-tree privileged EXEC command, see the  
command reference for this release.  
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C H A P T E R  
11  
Configuring Optional Spanning-Tree Features  
This chapter describes how to configure optional spanning-tree features on your Cisco Systems  
Intelligent Gigabit Ethernet Switch Module. You can configure all of these features when your switch  
is running the per-VLAN spanning-tree plus (PVST+). You can configure only the noted features when  
your switch is running the Multiple Spanning Tree Protocol (MSTP) or the rapid per-VLAN  
spanning-tree plus (rapid-PVST+) protocol.  
For information on configuring the PVST+ and rapid PVST+, see Chapter 9, “Configuring STP.” For  
information about the Multiple Spanning Tree Protocol (MSTP) and how to map multiple VLANs to the  
same spanning-tree instance, see Chapter 10, “Configuring MSTP.”  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
This chapter consists of these sections:  
•
•
•
Understanding Optional Spanning-Tree Features, page 11-1  
Configuring Optional Spanning-Tree Features, page 11-9  
Displaying the Spanning-Tree Status, page 11-17  
Understanding Optional Spanning-Tree Features  
These sections describe how the optional spanning-tree features work:  
•
•
•
•
•
•
•
•
Understanding Port Fast, page 11-2  
Understanding BPDU Guard, page 11-3  
Understanding BPDU Filtering, page 11-3  
Understanding UplinkFast, page 11-4  
Understanding BackboneFast, page 11-5  
Understanding EtherChannel Guard, page 11-8  
Understanding Root Guard, page 11-8  
Understanding Loop Guard, page 11-9  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Understanding Optional Spanning-Tree Features  
Understanding Port Fast  
Port Fast immediately brings an interface configured as an access or trunk port from a blocking state to  
the forwarding state, bypassing the listening and learning states. You can use Port Fast on ports  
connected to a single workstation or server, as shown in Figure 11-1, to allow those devices to  
immediately connect to the network, rather than waiting for the spanning tree to converge.  
Ports connected to a single workstation or server should not receive bridge protocol data units (BPDUs).  
A port with Port Fast enabled goes through the normal cycle of spanning-tree status changes when the  
switch is restarted.  
Note  
Because the purpose of Port Fast is to minimize the time ports must wait for spanning-tree to converge,  
it is effective only when used on ports connected to end stations. If you enable Port Fast on a port  
connected to another switch, you risk creating a spanning-tree loop.  
You can enable this feature by using the spanning-tree portfast interface configuration or the  
spanning-tree portfast default global configuration command.  
Figure 11-1  
Port Fast-Enabled Ports  
Catalyst 6000  
series switch  
Catalyst 3550  
switch  
Catalyst 2950, 2955,  
or 3550 switch  
Workstations  
BladeCenter  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Understanding Optional Spanning-Tree Features  
Understanding BPDU Guard  
The BPDU guard feature can be globally enabled on the switch or can be enabled per interface, but the  
feature operates with some differences.  
Caution  
You should use the BPDU guard feature only when one switch is deployed in the chassis. If two or more  
switches are in the chassis, do not enable the BPDU guard feature on the switches, either globally on  
each switch or on the individual management-module ports (ports 15 and 16) on the switches. This  
feature can put the management-module ports in the error-disabled state. The error-disabled state will  
shut down the management-module ports, causing a loss of communication with the switches.  
At the global level, you can enable BPDU guard on Port Fast-enabled ports by using the spanning-tree  
portfast bpduguard default global configuration command. Spanning tree shuts down ports that are in  
a Port Fast-operational state if any BPDU is received on those interfaces. In a valid configuration, Port  
Fast-enabled ports do not receive BPDUs. Receiving a BPDU on a Port Fast-enabled port signals an  
invalid configuration, such as the connection of an unauthorized device, and the BPDU guard feature  
puts the port in the error-disabled state.  
At the interface level, you can enable BPDU guard on any port by using the spanning-tree bpduguard  
enable interface configuration command without also enabling the Port Fast feature. When the port  
receives a BPDU, it is put in the error-disabled state.  
The BPDU guard feature provides a secure response to invalid configurations because you must  
manually put the port back in service. Use the BPDU guard feature in a service-provider network to  
prevent an access port from participating in the spanning tree.  
You can enable the BPDU guard feature for the entire switch or for an interface.  
Understanding BPDU Filtering  
The BPDU filtering feature can be globally enabled on the switch or can be enabled per interface, but  
the feature operates with some differences.  
At the global level, you can enable BPDU filtering on Port Fast-enabled ports by using the  
spanning-tree portfast bpdufilter default global configuration command. This command prevents  
ports that are in a Port Fast-operational state from sending or receiving BPDUs. The ports still send a  
few BPDUs at link-up before the switch begins to filter outbound BPDUs. You should globally enable  
BPDU filtering on a switch so that hosts connected to these ports do not receive BPDUs. If a BPDU is  
received on a Port Fast-enabled port, the port loses its Port Fast-operational status, and BPDU filtering  
is disabled.  
At the interface level, you can enable BPDU filtering on any port without also enabling the Port Fast  
feature by using the spanning-tree bpdufilter enable interface configuration command. This command  
prevents the port from sending or receiving BPDUs.  
Caution  
Enabling BPDU filtering on an interface is the same as disabling spanning tree on it and can result in  
spanning-tree loops.  
You can enable the BPDU filtering feature for the entire switch or for an interface.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Understanding Optional Spanning-Tree Features  
Understanding UplinkFast  
Switches in hierarchical networks can be grouped into backbone switches, distribution switches, and  
access switches. Figure 11-2 shows a complex network where distribution switches and access switches  
each have at least one redundant link that spanning tree blocks to prevent loops.  
Figure 11-2  
Switches in a Hierarchical Network  
Backbone switches  
Distribution switches  
Root bridge  
Catalyst 3550  
switches  
Catalyst 3550  
switches  
Active link  
Blocked link  
If a switch loses connectivity, it begins using the alternate paths as soon as the spanning tree selects a  
new root port. By enabling UplinkFast with the spanning-tree uplinkfast global configuration  
command, you can accelerate the choice of a new root port when a link or switch fails or when the  
spanning tree reconfigures itself. The root port transitions to the forwarding state immediately without  
going through the listening and learning states, as it would with the normal spanning-tree procedures.  
When the spanning tree reconfigures the new root port, other interfaces flood the network with multicast  
packets, one for each address that was learned on the interface. You can limit these bursts of multicast  
traffic by reducing the max-update-rate parameter (the default for this parameter is 150 packets per  
second). However, if you enter zero, station-learning frames are not generated, so the spanning-tree  
topology converges more slowly after a loss of connectivity.  
Note  
UplinkFast is most useful in wiring-closet switches at the access or edge of the network. It is not  
appropriate for backbone devices. This feature might not be useful for other types of applications.  
UplinkFast provides fast convergence after a direct link failure and achieves load balancing between  
redundant Layer 2 links using uplink groups. An uplink group is a set of Layer 2 interfaces (per VLAN),  
only one of which is forwarding at any given time. Specifically, an uplink group consists of the root port  
(which is forwarding) and a set of blocked ports, except for self-looping ports. The uplink group  
provides an alternate path in case the currently forwarding link fails.  
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Understanding Optional Spanning-Tree Features  
Figure 11-3 shows an example topology with no link failures. Switch A, the root switch, is connected  
directly to Switch B over link L1 and to Switch C over link L2. The Layer 2 interface on Switch C that  
is connected directly to Switch B is in a blocking state.  
Figure 11-3  
UplinkFast Example Before Direct Link Failure  
Switch A  
(Root)  
Switch B  
L1  
L2  
L3  
Blocked port  
Switch C  
If Switch C detects a link failure on the currently active link L2 on the root port (a direct link failure),  
UplinkFast unblocks the blocked port on Switch C and transitions it to the forwarding state without  
going through the listening and learning states, as shown in Figure 11-4. This change takes  
approximately 1 to 5 seconds.  
Figure 11-4  
UplinkFast Example After Direct Link Failure  
Switch A  
(Root)  
Switch B  
L1  
L2  
Link failure  
L3  
UplinkFast transitions port  
directly to forwarding state.  
Switch C  
Understanding BackboneFast  
BackboneFast detects indirect failures in the core of the backbone. BackboneFast is a complementary  
technology to the UplinkFast feature, which responds to failures on links directly connected to access  
switches. BackboneFast optimizes the maximum-age timer, which determines the amount of time the  
switch stores protocol information received on an interface. When a switch receives an inferior BPDU  
from the designated port of another switch, the BPDU is a signal that the other switch might have lost  
its path to the root, and BackboneFast tries to find an alternate path to the root.  
BackboneFast, which is enabled by using the spanning-tree backbonefast global configuration  
command, starts when a root port or blocked port on a switch receives inferior BPDUs from its  
designated switch. An inferior BPDU identifies a switch that declares itself as both the root bridge and  
the designated switch. When a switch receives an inferior BPDU, it means that a link to which the switch  
is not directly connected (an indirect link) has failed (that is, the designated bridge has lost its connection  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Understanding Optional Spanning-Tree Features  
to the root switch). Under spanning-tree rules, the switch ignores inferior BPDUs for the configured  
maximum aging time specified by the spanning-tree vlan vlan-id max-age global configuration  
command.  
The switch tries to determine if it has an alternate path to the root switch. If the inferior BPDU arrives  
on a blocked port, the root port and other blocked ports on the switch become alternate paths to the root  
switch. (Self-looped ports are not considered alternate paths to the root switch.) If the inferior BPDU  
arrives on the root port, all blocked ports become alternate paths to the root switch. If the inferior BPDU  
arrives on the root port and there are no blocked ports, the switch assumes that it has lost connectivity  
to the root switch, causes the maximum aging time on the root port to expire, and becomes the root  
switch according to normal spanning-tree rules.  
If the switch has alternate paths to the root switch, it uses these alternate paths to send a root link query  
(RLQ) request. The switch sends the RLQ request on all alternate paths to the root switch and waits for  
an RLQ reply from other switches in the network.  
If the switch determines that it still has an alternate path to the root, it expires the maximum aging time  
on the port that received the inferior BPDU. If all the alternate paths to the root switch indicate that the  
switch has lost connectivity to the root switch, the switch expires the maximum aging time on the port  
that received the RLQ reply. If one or more alternate paths can still connect to the root switch, the switch  
makes all ports on which it received an inferior BPDU its designated ports and moves them from the  
blocking state (if they were in the blocking state), through the listening and learning states, and into the  
forwarding state.  
Figure 11-5 shows an example topology with no link failures. Switch A, the root switch, connects  
directly to Switch B over link L1 and to Switch C over link L2. The Layer 2 interface on Switch C that  
connects directly to Switch B is in the blocking state.  
Figure 11-5  
BackboneFast Example Before Indirect Link Failure  
Switch A  
(Root)  
Switch B  
L1  
L2  
L3  
Blocked port  
Switch C  
If link L1 fails as shown in Figure 11-6, Switch C cannot detect this failure because it is not connected  
directly to link L1. However, because Switch B is directly connected to the root switch over L1, it detects  
the failure, elects itself the root, and begins sending BPDUs to Switch C, identifying itself as the root.  
When Switch C receives the inferior BPDUs from Switch B, Switch C assumes that an indirect failure  
has occurred. At that point, BackboneFast allows the blocked port on Switch C to move immediately to  
the listening state without waiting for the maximum aging time for the port to expire. BackboneFast then  
transitions the Layer 2 interface on Switch C to the forwarding state, providing a path from Switch B to  
Switch A. This switchover takes approximately 30 seconds, twice the Forward Delay time if the default  
Forward Delay time of 15 seconds is set. Figure 11-6 shows how BackboneFast reconfigures the  
topology to account for the failure of link L1.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Understanding Optional Spanning-Tree Features  
Figure 11-6  
BackboneFast Example After Indirect Link Failure  
Switch A  
(Root)  
Switch B  
L1  
Link failure  
L2  
L3  
BackboneFast changes port  
through listening and learning  
states to forwarding state.  
Switch C  
If a new switch is introduced into a shared-medium topology as shown in Figure 11-7, BackboneFast is  
not activated because the inferior BPDUs did not come from the recognized designated bridge  
(Switch B). The new switch begins sending inferior BPDUs that indicate it is the root switch. However,  
the other switches ignore these inferior BPDUs, and the new switch learns that Switch B is the  
designated bridge to Switch A, the root switch.  
Figure 11-7  
Adding a Switch in a Shared-Medium Topology  
Switch A  
(Root)  
Switch B  
(Designated bridge)  
Switch C  
Blocked port  
Added switch  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Understanding Optional Spanning-Tree Features  
Understanding EtherChannel Guard  
You can use EtherChannel guard to detect an EtherChannel misconfiguration between the switch and a  
connected device. A misconfiguration can occur if the switch interfaces are configured in an  
EtherChannel, but the interfaces on the other device are not. A misconfiguration can also occur if the  
channel parameters are not the same at both ends of the EtherChannel. For EtherChannel configuration  
guidelines, see the “EtherChannel Configuration Guidelines” section on page 24-8.  
If the switch detects a misconfiguration on the other device, EtherChannel guard places the switch  
interfaces in the error-disabled state, and this error message appears:  
PM-4-ERR_DISABLE: Channel-misconfig error detected on [chars], putting [chars] in  
err-disable state.  
You can enable this feature by using the spanning-tree etherchannel guard misconfig global  
configuration command.  
Understanding Root Guard  
The Layer 2 network of a service provider (SP) can include many connections to switches that are not  
owned by the SP. In such a topology, the spanning tree can reconfigure itself and select a customer  
switch as the root switch, as shown in Figure 11-8. You can avoid this situation by enabling root guard  
on SP switch interfaces that connect to switches in your customer’s network. If spanning-tree  
calculations cause an interface in the customer network to be selected as the root port, root guard then  
places the interface in the root-inconsistent (blocked) state to prevent the customer’s switch from  
becoming the root switch or being in the path to the root.  
If a switch outside the SP network becomes the root switch, the interface is blocked (root-inconsistent  
state), and spanning tree selects a new root switch. The customer’s switch does not become the root  
switch and is not in the path to the root.  
If the switch is operating in multiple spanning-tree (MST) mode, root guard forces the port to be a  
designated port. If a boundary port is blocked in an internal spanning-tree (IST) instance because of root  
guard, the port also is blocked in all MST instances. A boundary port is a port that connects to a LAN,  
the designated switch of which is either an IEEE 802.1D switch or a switch with a different MST region  
configuration.  
Root guard enabled on an interface applies to all the VLANs to which the interface belongs. VLANs can  
be grouped and mapped to an MST instance.  
You can enable this feature by using the spanning-tree guard root interface configuration command.  
Caution  
Misuse of the root-guard feature can cause a loss of connectivity.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Configuring Optional Spanning-Tree Features  
Figure 11-8  
Root Guard in a Service-Provider Network  
Customer network  
Service-provider network  
Potential  
spanning-tree root without  
root guard enabled  
Desired  
root switch  
Enable the root-guard feature  
on these interfaces to prevent  
switches in the customer  
network from becoming  
the root switch or being  
in the path to the root.  
Understanding Loop Guard  
You can use loop guard to prevent alternate or root ports from becoming designated ports because of a  
failure that leads to a unidirectional link. This feature is most effective when it is configured on the entire  
switched network.  
You can enable this feature by using the spanning-tree loopguard default global configuration  
command.  
When the switch is operating in PVST+ or rapid-PVST+ mode, loop guard prevents alternate and root  
ports from becoming designated ports, and spanning tree does not send BPDUs on root or alternate ports.  
When the switch is operating in MST mode, BPDUs are not sent on nonboundary ports only if the port  
is blocked by loop guard in all MST instances. On a boundary port, loop guard blocks the port in all MST  
instances.  
Configuring Optional Spanning-Tree Features  
These sections describe how to configure optional spanning-tree features:  
•
•
•
•
•
•
•
•
Default Optional Spanning-Tree Configuration, page 11-10  
Optional Spanning-Tree Configuration Guidelines, page 11-10  
Enabling Port Fast, page 11-10 (optional)  
Enabling BPDU Guard, page 11-11 (optional)  
Enabling BPDU Filtering, page 11-12 (optional)  
Enabling UplinkFast for Use with Redundant Links, page 11-13 (optional)  
Enabling BackboneFast, page 11-14 (optional)  
Enabling EtherChannel Guard, page 11-15 (optional)  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Configuring Optional Spanning-Tree Features  
•
•
Enabling Root Guard, page 11-15 (optional)  
Enabling Loop Guard, page 11-16 (optional)  
Default Optional Spanning-Tree Configuration  
Table 11-1 shows the default optional spanning-tree configuration.  
Table 11-1  
Default Optional Spanning-Tree Configuration  
Feature  
Default Setting  
Disabled.  
BPDU guard  
BPDU filtering  
Port Fast  
Enabled.  
Enabled.  
UplinkFast  
BackboneFast  
Globally disabled.  
Globally disabled.  
EtherChannel guard  
Root guard  
Globally enabled.  
Disabled on all interfaces.  
Disabled on all interfaces.  
Loop guard  
Optional Spanning-Tree Configuration Guidelines  
You can configure PortFast, BPDU guard, BPDU filtering, EtherChannel guard, root guard, or loop  
guard if your switch is running PVST+, rapid PVST+, or MSTP.  
You can configure the UplinkFast or the BackboneFast feature for rapid PVST+ or for the MSTP, but  
the feature remains disabled (inactive) until you change the spanning-tree mode to PVST+.  
Enabling Port Fast  
A port with the Port Fast feature enabled is moved directly to the spanning-tree forwarding state without  
waiting for the standard forward-time delay.  
Caution  
Use Port Fast only when connecting a single end station to an access or trunk port. Enabling this feature  
on a port connected to a switch or hub could prevent spanning tree from detecting and disabling loops  
in your network, which could cause broadcast storms and address-learning problems.  
If you enable the voice VLAN feature, the Port Fast feature is automatically enabled. When you disable  
voice VLAN, the Port Fast feature is not automatically disabled.  
You can enable this feature if your switch is running PVST+, rapid PVST+, or MSTP.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Configuring Optional Spanning-Tree Features  
Beginning in privileged EXEC mode, follow these steps to enable Port Fast. This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify an interface to configure, and enter interface  
configuration mode.  
Step 3  
spanning-tree portfast [trunk]  
Enable Port Fast on an access port connected to a single  
workstation or server. By specifying the trunk keyword, you can  
enable Port Fast on a trunk port.  
Note  
To enable Port Fast on trunk ports, you must use the  
spanning-tree portfast trunk interface configuration  
command. The spanning-tree portfast command will  
not work on trunk ports.  
Caution  
Make sure that there are no loops in the network  
between the trunk port and the workstation or server  
before you enable Port Fast on a trunk port.  
By default, Port Fast is disabled on all ports.  
Return to privileged EXEC mode.  
Verify your entries.  
Step 4  
Step 5  
end  
show spanning-tree interface interface-id  
portfast  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Note  
You can use the spanning-tree portfast default global configuration command to globally enable the  
Port Fast feature on all nontrunking ports.  
To disable the Port Fast feature, use the spanning-tree portfast disable interface configuration  
command.  
Enabling BPDU Guard  
When you globally enable BPDU guard on ports that are Port Fast-enabled (the ports are in a Port  
Fast-operational state), spanning tree shuts down Port Fast-enabled ports that receive BPDUs.  
In a valid configuration, Port Fast-enabled ports do not receive BPDUs. Receiving a BPDU on a Port  
Fast-enabled port signals an invalid configuration, such as the connection of an unauthorized device, and  
the BPDU guard feature puts the port in the error-disabled state. The BPDU guard feature provides a  
secure response to invalid configurations because you must manually put the port back in service. Use  
the BPDU guard feature in a service-provider network to prevent an access port from participating in the  
spanning tree.  
Caution  
Configure Port Fast only on ports that connect to end stations; otherwise, an accidental topology loop  
could cause a data packet loop and disrupt switch and network operation.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Configuring Optional Spanning-Tree Features  
You can also use the spanning-tree bpduguard enable interface configuration command to enable  
BPDU guard on any port without also enabling the Port Fast feature. When the port receives a BPDU, it  
is put in the error-disabled state.  
You can enable the BPDU guard feature if your switch is running PVST+, rapid PVST+, or MSTP.  
Beginning in privileged EXEC mode, follow these steps to globally enable the BPDU guard feature. This  
procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Globally enable BPDU guard.  
spanning-tree portfast bpduguard default  
By default, BPDU guard is disabled.  
Step 3  
interface interface-id  
Specify the interface connected to an end station, and enter  
interface configuration mode.  
Step 4  
Step 5  
Step 6  
Step 7  
spanning-tree portfast  
end  
Enable the Port Fast feature.  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable BPDU guard, use the no spanning-tree portfast bpduguard default global configuration  
command.  
You can override the setting of the no spanning-tree portfast bpduguard default global configuration  
command by using the spanning-tree bpduguard enable interface configuration command.  
Enabling BPDU Filtering  
When you globally enable BPDU filtering on Port Fast-enabled ports, it prevents ports that are in a Port  
Fast-operational state from sending or receiving BPDUs. The ports still send a few BPDUs at link-up  
before the switch begins to filter outbound BPDUs. You should globally enable BPDU filtering on a  
switch so that hosts connected to these ports do not receive BPDUs. If a BPDU is received on a Port  
Fast-enabled port, the port loses its Port Fast-operational status, and BPDU filtering is disabled.  
Caution  
Configure Port Fast only on ports that connect to end stations; otherwise, an accidental topology loop  
could cause a data packet loop and disrupt switch and network operation.  
You can also use the spanning-tree bpdufilter enable interface configuration command to enable  
BPDU filtering on any port without also enabling the Port Fast feature. This command prevents the port  
from sending or receiving BPDUs.  
Caution  
Enabling BPDU filtering on an interface is the same as disabling spanning tree on it and can result in  
spanning-tree loops.  
You can enable the BPDU filtering feature if your switch is running PVST+, rapid PVST+, or MSTP.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Configuring Optional Spanning-Tree Features  
Beginning in privileged EXEC mode, follow these steps to globally enable the BPDU filtering feature.  
This procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Globally enable BPDU filtering.  
By default, BPDU filtering is disabled.  
spanning-tree portfast bpdufilter default  
Step 3  
interface interface-id  
Specify the interface connected to an end station, and enter  
interface configuration mode.  
Step 4  
Step 5  
Step 6  
Step 7  
spanning-tree portfast  
end  
Enable the Port Fast feature.  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable BPDU filtering, use the no spanning-tree portfast bpdufilter default global configuration  
command.  
You can override the setting of the no spanning-tree portfast bpdufilter default global configuration  
command by using the spanning-tree bpdufilter enable interface configuration command.  
Enabling UplinkFast for Use with Redundant Links  
UplinkFast cannot be enabled on VLANs that have been configured for switch priority. To enable  
UplinkFast on a VLAN with switch priority configured, first restore the switch priority on the VLAN to  
the default value by using the no spanning-tree vlan vlan-id priority global configuration command.  
Note  
When you enable UplinkFast, it affects all VLANs on the switch. You cannot configure UplinkFast on  
an individual VLAN.  
You can enable the UplinkFast feature for rapid PVST+ or for the MSTP, but the feature remains  
disabled (inactive) until you change the spanning-tree mode to PVST+.  
Beginning in privileged EXEC mode, follow these steps to enable UplinkFast. This procedure is  
optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
spanning-tree uplinkfast [max-update-rate Enable UplinkFast.  
pkts-per-second]  
(Optional) For pkts-per-second, the range is 0 to 32000 packets per  
second; the default is 150.  
If you set the rate to 0, station-learning frames are not generated,  
and the spanning-tree topology converges more slowly after a loss  
of connectivity.  
Step 3  
end  
Return to privileged EXEC mode.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Configuring Optional Spanning-Tree Features  
Command  
Purpose  
Step 4  
Step 5  
show spanning-tree summary  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
When UplinkFast is enabled, the switch priority of all VLANs is set to 49152. If you change the path  
cost to a value less than 3000 and you enable UplinkFast or UplinkFast is already enabled, the path cost  
of all interfaces and VLAN trunks is increased by 3000 (if you change the path cost to 3000 or above,  
the path cost is not altered). The changes to the switch priority and the path cost reduces the chance that  
the switch will become the root switch.  
When UplinkFast is disabled, the switch priorities of all VLANs and path costs of all interfaces are set  
to default values if you did not modify them from their defaults.  
To return the update packet rate to the default setting, use the no spanning-tree uplinkfast  
max-update-rate global configuration command. To disable UplinkFast, use the no spanning-tree  
uplinkfast command.  
Enabling BackboneFast  
You can enable BackboneFast to detect indirect link failures and to start the spanning-tree  
reconfiguration sooner.  
Note  
If you use BackboneFast, you must enable it on all switches in the network. BackboneFast is not  
supported on Token Ring VLANs. This feature is supported for use with third-party switches.  
You can enable the BackboneFast feature for rapid PVST+ or for the MSTP, but the feature remains  
disabled (inactive) until you change the spanning-tree mode to PVST+.  
Beginning in privileged EXEC mode, follow these steps to enable BackboneFast. This procedure is  
optional.  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
Step 5  
configure terminal  
Enter global configuration mode.  
Enable BackboneFast.  
spanning-tree backbonefast  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree summary  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable the BackboneFast feature, use the no spanning-tree backbonefast global configuration  
command.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Configuring Optional Spanning-Tree Features  
Enabling EtherChannel Guard  
You can enable EtherChannel guard to detect an EtherChannel misconfiguration if your switch is  
running PVST+, rapid PVST+, or MSTP.  
Beginning in privileged EXEC mode, follow these steps to enable EtherChannel guard. This procedure  
is optional.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Enable EtherChannel guard.  
spanning-tree etherchannel guard  
misconfig  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show spanning-tree summary  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable the EtherChannel guard feature, use the no spanning-tree etherchannel guard misconfig  
global configuration command.  
You can use the show interfaces status err-disabled privileged EXEC command to show which switch  
ports are disabled because of an EtherChannel misconfiguration. On the remote device, you can enter  
the show etherchannel summary privileged EXEC command to verify the EtherChannel configuration.  
After the configuration is corrected, enter the shutdown and no shutdown interface configuration  
commands on the port-channel interfaces that were misconfigured.  
Enabling Root Guard  
Root guard enabled on an interface applies to all the VLANs to which the interface belongs.  
Do not enable the root guard on interfaces to be used by the UplinkFast feature. With UplinkFast, the  
backup interfaces (in the blocked state) replace the root port in the case of a failure. However, if root  
guard is also enabled, all the backup interfaces used by the UplinkFast feature are placed in the  
root-inconsistent state (blocked) and are prevented from reaching the forwarding state.  
Note  
You cannot enable both root guard and loop guard at the same time.  
You can enable this feature if your switch is running PVST+, rapid PVST+, or MSTP.  
Beginning in privileged EXEC mode, follow these steps to enable root guard on an interface. This  
procedure is optional.  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
Enter global configuration mode.  
interface interface-id  
spanning-tree guard root  
Specify an interface to configure, and enter interface configuration mode.  
Enable root guard on the interface.  
By default, root guard is disabled on all interfaces.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Configuring Optional Spanning-Tree Features  
Command  
Purpose  
Step 4  
end  
Return to privileged EXEC mode.  
Verify your entries.  
Step 5  
Step 6  
show running-config  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To disable root guard, use the no spanning-tree guard interface configuration command.  
Enabling Loop Guard  
You can use loop guard to prevent alternate or root ports from becoming designated ports because of a  
failure that leads to a unidirectional link. This feature is most effective when it is configured on the entire  
switched network. Loop guard operates only on ports that are considered point-to-point by the spanning  
tree.  
Note  
You cannot enable both loop guard and root guard at the same time.  
You can enable this feature if your switch is running PVST+, rapid PVST+, or MSTP.  
Beginning in privileged EXEC mode, follow these steps to enable loop guard. This procedure is optional.  
Command  
Purpose  
Step 1  
show spanning-tree active  
or  
Determine which ports are alternate or root ports.  
show spanning-tree mst  
configure terminal  
spanning-tree loopguard default  
Step 2  
Step 3  
Enter global configuration mode.  
Enable loop guard.  
By default, loop guard is disabled.  
Return to privileged EXEC mode.  
Verify your entries.  
Step 4  
Step 5  
Step 6  
end  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To globally disable loop guard, use the no spanning-tree loopguard default global configuration  
command. You can override the setting of the no spanning-tree loopguard default global configuration  
command by using the spanning-tree guard loop interface configuration command.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Displaying the Spanning-Tree Status  
Displaying the Spanning-Tree Status  
To display the spanning-tree status, use one or more of the privileged EXEC commands in Table 11-2:  
Table 11-2  
Commands for Displaying the Spanning-Tree Status  
Command  
Purpose  
show spanning-tree active  
Displays spanning-tree information on active interfaces only.  
Displays a detailed summary of interface information.  
Displays spanning-tree information for the specified interface.  
Displays MST information for the specified interface.  
show spanning-tree detail  
show spanning-tree interface interface-id  
show spanning-tree mst interface interface-id  
show spanning-tree summary [totals]  
Displays a summary of port states or displays the total lines of the  
spanning-tree state section.  
You can clear spanning-tree counters by using the clear spanning-tree [interface interface-id]  
privileged EXEC command.  
For information about other keywords for the show spanning-tree privileged EXEC command, see the  
command reference for this release.  
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Chapter 11 Configuring Optional Spanning-Tree Features  
Displaying the Spanning-Tree Status  
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C H A P T E R  
12  
Configuring VLANs  
This chapter describes how to configure normal-range VLANs on your Cisco Systems Intelligent  
Gigabit Ethernet Switch Module. It includes information about VLAN modes and the VLAN  
Membership Policy Server (VMPS).  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
The chapter includes these sections:  
•
•
•
•
•
•
Understanding VLANs, page 12-1  
Configuring Normal-Range VLANs, page 12-4  
Configuring Extended-Range VLANs, page 12-11  
Displaying VLANs, page 12-13  
Configuring VLAN Trunks, page 12-14  
Configuring VMPS, page 12-25  
Understanding VLANs  
A VLAN is a switched network that is logically segmented by function, project team, or application,  
without regard to the physical locations of the users. VLANs have the same attributes as physical LANs,  
but you can group end stations even if they are not physically located on the same LAN segment. Any  
switch port can belong to a VLAN, and unicast, broadcast, and multicast packets are forwarded and  
flooded only to end stations in the VLAN. Each VLAN is considered a logical network, and packets  
destined for stations that do not belong to the VLAN must be forwarded through a router or bridge as  
shown in Figure 12-1. Because a VLAN is considered a separate logical network, it contains its own MIB  
information and can support its own implementation of spanning tree. See Chapter 9, “Configuring STP”  
and Chapter 10, “Configuring MSTP.”  
Note  
Before you create VLANs, you must decide whether to use VLAN Trunking Protocol (VTP) to maintain  
global VLAN configuration for your network. For more information on VTP, see Chapter 13,  
“Configuring VTP.”  
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Chapter 12 Configuring VLANs  
Understanding VLANs  
Figure 12-1 shows an example of VLANs segmented into logically defined networks.  
Figure 12-1  
VLANs as Logically Defined Networks  
Cisco router  
Floor 3  
Ethernet  
Floor 2  
Floor 1  
VLANs are often associated with IP subnetworks. For example, all the end stations in a particular IP  
subnet belong to the same VLAN. Interface VLAN membership on the switch is assigned manually on  
an interface-by-interface basis. When you assign switch interfaces to VLANs by using this method, it is  
known as interface-based, or static, VLAN membership.  
Supported VLANs  
The switches support 250 VLANs. VLANs are identified with a number from 1 to 4094. VLAN IDs 1002  
through 1005 are reserved for Token Ring and FDDI VLANs. VTP only learns normal-range VLANs,  
with VLAN IDs 1 to 1005; VLAN IDs greater than 1005 are extended-range VLANs and are not stored  
in the VLAN database. The switch must be in VTP transparent mode when you create VLAN IDs from  
1006 to 4094.  
The switch supports per-VLAN spanning-tree plus (PVST+) and rapid PVST+ with a maximum of 64  
spanning-tree instances. One spanning-tree instance is allowed per VLAN. See the “Normal-Range  
VLAN Configuration Guidelines” section on page 12-5 for more information about the number of  
spanning-tree instances and the number of VLANs. The switch supports IEEE 802.1Q trunking for  
sending VLAN traffic over Ethernet ports.  
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Chapter 12 Configuring VLANs  
Understanding VLANs  
VLAN Port Membership Modes  
You configure a port to belong to a VLAN by assigning a membership mode that determines the kind of  
traffic the port carries and the number of VLANs to which it can belong. Table 12-1 lists the membership  
modes and membership and VTP characteristics.  
Table 12-1  
Port Membership Modes  
Membership Mode VLAN Membership Characteristics  
VTP Characteristics  
Static-access  
A static-access port can belong to one VLAN and is  
VTP is not required. If you do not want  
manually assigned to that VLAN. For more information, VTP to globally propagate information, set  
see the “Assigning Static-Access Ports to a VLAN”  
section on page 12-10.  
the VTP mode to transparent to disable  
VTP. To participate in VTP, there must be  
at least one trunk port on the switch  
connected to a trunk port of a second  
switch.  
A trunk port is a member of all VLANs by default,  
VTP is recommended but not required.  
including extended-range VLANs, but membership can be VTP maintains VLAN configuration  
limited by configuring the allowed-VLAN list. You can  
also modify the pruning-eligible list to block flooded  
traffic to VLANs on trunk ports that are included in the  
consistency by managing the addition,  
deletion, and renaming of VLANs on a  
network-wide basis. VTP exchanges  
list. For information about configuring trunk ports, see the VLAN configuration messages with other  
“Configuring an Ethernet Interface as a Trunk Port”  
section on page 12-17.  
switches over trunk links.  
Dynamic access  
A dynamic-access port can belong to one VLAN (VLAN VTP is required.  
ID 1 to 4094), and is dynamically assigned by a VMPS.  
Configure the VMPS and the client with the  
The VMPS can be a Catalyst 5000 or Catalyst 6500 series  
switch, for example, but never a Cisco Systems Intelligent  
Gigabit Ethernet Switch Module.  
same VTP domain name.  
You can change the reconfirmation interval  
and retry count on the VMPS client switch.  
You can have dynamic-access ports and trunk ports on the  
same switch, but you must connect the dynamic-access  
port to an end station and not to another switch.  
For configuration information, see the “Configuring  
Dynamic Access Ports on VMPS Clients” section on  
page 12-28.  
Voice VLAN  
A voice VLAN port is an access port attached to a Cisco VTP is not required; it has no affect on  
IP Phone, configured to use one VLAN for voice traffic  
and another VLAN for data traffic from a device attached  
to the phone.  
voice VLAN.  
For more detailed definitions of the modes and their functions, see Table 12-4 on page 12-15.  
When a port belongs to a VLAN, the switch learns and manages the addresses associated with the port  
on a per-VLAN basis. For more information, see the “Managing the MAC Address Table” section on  
page 4-18.  
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Chapter 12 Configuring VLANs  
Configuring Normal-Range VLANs  
Configuring Normal-Range VLANs  
Normal-range VLANs are VLANs with VLAN IDs 1 to 1005. If the switch is in VTP server or  
transparent mode, you can add, modify or remove configurations for VLANs 2 to 1001 in the VLAN  
database. (VLAN IDs 1 and 1002 to 1005 are automatically created and cannot be removed.)  
Note  
When the switch is in VTP transparent mode, you can also create extended-range VLANs (VLANs with  
IDs from 1006 to 4094), but these VLANs are not saved in the VLAN database. See the “Configuring  
Extended-Range VLANs” section on page 12-11.  
Configurations for VLAN IDs 1 to 1005 are written to the file vlan.dat (VLAN database), and you can  
display them by entering the show vlan privileged EXEC command. The vlan.dat file is stored in Flash  
memory.  
Caution  
You can cause inconsistency in the VLAN database if you attempt to manually delete the vlan.dat file.  
If you want to modify the VLAN configuration, use the commands described in these sections and in the  
command reference for this release. To change the VTP configuration, see Chapter 13, “Configuring  
VTP.”  
You use the interface configuration mode to define the port membership mode and to add and remove  
ports from VLANs. The results of these commands are written to the running-configuration file, and you  
can display the file by entering the show running-config privileged EXEC command.  
You can set these parameters when you create a new normal-range VLAN or modify an existing VLAN  
in the VLAN database:  
•
•
•
VLAN ID  
VLAN name  
VLAN type (Ethernet, Fiber Distributed Data Interface [FDDI], FDDI network entity title [NET],  
TrBRF, or TrCRF, Token Ring, Token Ring-Net)  
•
•
•
•
•
•
•
•
VLAN state (active or suspended)  
Maximum transmission unit (MTU) for the VLAN  
Security Association Identifier (SAID)  
Bridge identification number for TrBRF VLANs  
Ring number for FDDI and TrCRF VLANs  
Parent VLAN number for TrCRF VLANs  
Spanning Tree Protocol (STP) type for TrCRF VLANs  
VLAN number to use when translating from one VLAN type to another  
Note  
This section does not provide configuration details for most of these parameters. For complete  
information on the commands and parameters that control VLAN configuration, see the command  
reference for this release.  
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Chapter 12 Configuring VLANs  
Configuring Normal-Range VLANs  
This section includes information about these topics about normal-range VLANs:  
•
•
•
•
•
•
•
•
Token Ring VLANs, page 12-5  
Normal-Range VLAN Configuration Guidelines, page 12-5  
VLAN Configuration Mode Options, page 12-6  
Saving VLAN Configuration, page 12-7  
Default Ethernet VLAN Configuration, page 12-7  
Creating or Modifying an Ethernet VLAN, page 12-8  
Deleting a VLAN, page 12-10  
Assigning Static-Access Ports to a VLAN, page 12-10  
Token Ring VLANs  
Although the switch does not support Token Ring connections, a remote device such as a Catalyst 5000  
series switch with Token Ring connections could be managed from one of the supported switches.  
Switches running VTP version 2 advertise information about these Token Ring VLANs:  
•
•
Token Ring TrBRF VLANs  
Token Ring TrCRF VLANs  
For more information on configuring Token Ring VLANs, see the Catalyst 5000 Series Software  
Configuration Guide.  
Normal-Range VLAN Configuration Guidelines  
Follow these guidelines when creating and modifying normal-range VLANs in your network:  
•
•
•
Normal-range VLANs are identified with a number between 1 and 1001. VLAN numbers 1002  
through 1005 are reserved for Token Ring and FDDI VLANs.  
VLAN configuration for VLANs 1 to 1005 are always saved in the VLAN database. If VTP mode  
is transparent, VTP and VLAN configuration are also saved in the switch running configuration file.  
The switch also supports VLAN IDs 1006 through 4094 in VTP transparent mode (VTP disabled).  
These are extended-range VLANs, and configuration options are limited. Extended-range VLANs  
are not saved in the VLAN database. See the “Configuring Extended-Range VLANs” section on  
page 12-11.  
•
•
•
Before you can create a VLAN, the switch must be in VTP server mode or VTP transparent mode.  
If the switch is a VTP server, you must define a VTP domain, or VTP will not function.  
The switch does not support Token Ring or FDDI media. The switch does not forward FDDI,  
FDDI-Net, TrCRF, or TrBRF traffic, but it does propagate the VLAN configuration through VTP.  
The switch supports 64 spanning-tree instances. If a switch has more active VLANs than supported  
spanning-tree instances, spanning tree can be enabled on 64 VLANs and is disabled on the  
remaining VLANs. If you have already used all available spanning-tree instances on a switch,  
adding another VLAN anywhere in the VTP domain creates a VLAN on that switch that is not  
running spanning tree. If you have the default allowed list on the trunk ports of that switch (which  
is to allow all VLANs), the new VLAN is carried on all trunk ports. Depending on the topology of  
the network, this could create a loop in the new VLAN that would not be broken, particularly if there  
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Chapter 12 Configuring VLANs  
Configuring Normal-Range VLANs  
are several adjacent switches that all have run out of spanning-tree instances. You can prevent this  
possibility by setting allowed lists on the trunk ports of switches that have used up their allocation  
of spanning-tree instances.  
If the number of VLANs on the switch exceeds the number of supported spanning tree instances, we  
recommend that you configure the IEEE 802.1S Multiple STP (MSTP) on your switch to map  
multiple VLANs to a single STP instance. For more information about MSTP, see Chapter 10,  
“Configuring MSTP.”  
VLAN Configuration Mode Options  
You can configure normal-range VLANs (with VLAN IDs 1 to 1005) by using these two configuration  
modes:  
•
•
VLAN Configuration in config-vlan Mode, page 12-6  
You access config-vlan mode by entering the vlan vlan-id global configuration command.  
VLAN Configuration in VLAN Configuration Mode, page 12-6  
You access VLAN database configuration mode by entering the vlan database privileged EXEC  
command.  
VLAN Configuration in config-vlan Mode  
To access config-vlan mode, enter the vlan global configuration command with a VLAN ID. Enter a new  
VLAN ID to create a VLAN or with an existing VLAN ID to modify the VLAN. You can use the default  
VLAN configuration (Table 12-2) or enter multiple commands to configure the VLAN. For more  
information about commands available in this mode, see the vlan global configuration command  
description in the command reference for this release. When you have finished the configuration, you  
must exit config-vlan mode for the configuration to take effect. To display the VLAN configuration,  
enter the show vlan privileged EXEC command.  
You must use this config-vlan mode when creating extended-range VLANs (VLAN IDs greater than  
1005). See the “Configuring Extended-Range VLANs” section on page 12-11.  
VLAN Configuration in VLAN Configuration Mode  
To access VLAN configuration mode, enter the vlan database privileged EXEC command. Then enter  
the vlan command with a new VLAN ID to create a VLAN or with an existing VLAN ID to modify the  
VLAN. You can use the default VLAN configuration (Table 12-2) or enter multiple commands to  
configure the VLAN. For more information about keywords available in this mode, see the vlan VLAN  
configuration command description in the command reference for this release. When you have finished  
the configuration, you must enter apply or exit for the configuration to take effect. When you enter the  
exit command, it applies all commands and updates the VLAN database. VTP messages are sent to other  
switches in the VTP domain, and the privileged EXEC mode prompt appears.  
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Chapter 12 Configuring VLANs  
Configuring Normal-Range VLANs  
Saving VLAN Configuration  
The configurations of VLAN IDs 1 to 1005 are always saved in the VLAN database (vlan.dat file). If  
VTP mode is transparent, they are also saved in the switch running configuration file, and you can enter  
the copy running-config startup-config privileged EXEC command to save the configuration in the  
startup configuration file. You can use the show running-config vlan privileged EXEC command to  
display the switch running configuration file. To display the VLAN configuration, enter the show vlan  
privileged EXEC command.  
When you save VLAN and VTP information (including extended-range VLAN configuration  
information) in the startup configuration file and reboot the switch, the switch configuration is  
determined as follows:  
•
If the VTP mode is transparent in the startup configuration, and the VLAN database and the VTP  
domain name from the VLAN database matches that in the startup configuration file, the VLAN  
database is ignored (cleared). The VTP and VLAN configurations in the startup configuration file  
are used. The VLAN database revision number remains unchanged in the VLAN database.  
•
•
If the VTP mode or domain name in the startup configuration does not match the VLAN database,  
the domain name and VTP mode and configuration for the first 1005 VLAN IDs use the VLAN  
database information.  
If the VTP mode is server, the domain name and VLAN configuration for the first 1005 VLAN IDs  
use the VLAN database information.  
Caution  
If the VLAN database configuration is used at startup and the startup configuration file contains  
extended-range VLAN configuration, this information is lost when the system boots up.  
Default Ethernet VLAN Configuration  
Table 12-2 shows the default configuration for Ethernet VLANs.  
Note  
The switch supports Ethernet interfaces exclusively. Because FDDI and Token Ring VLANs are not  
locally supported, you only configure FDDI and Token Ring media-specific characteristics for VTP  
global advertisements to other switches.  
Table 12-2  
Ethernet VLAN Defaults and Ranges  
Parameter  
Default  
Range  
VLAN ID  
1 (for the internal 100 Mbps  
management module ports)  
No range  
2 (for the internal 1000 Mbps  
ports and the external ports)  
No range  
No range  
VLAN name  
For VLAN 1: default  
For VLAN 2: operational  
IEEE 802.10 SAID  
MTU size  
100001 (100000 plus the  
VLAN ID)  
1 to 4294967294  
1500 to 18190  
1500  
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Chapter 12 Configuring VLANs  
Configuring Normal-Range VLANs  
Table 12-2  
Ethernet VLAN Defaults and Ranges (continued)  
Parameter  
Default  
Range  
Translational bridge 1  
0
0–1005  
Translational bridge 2  
VLAN state  
0
0–1005  
For VLAN 1: active  
For VLAN 2: active  
disabled  
active, suspend  
Remote SPAN  
enabled, disabled  
Creating or Modifying an Ethernet VLAN  
Each Ethernet VLAN in the VLAN database has a unique, 4-digit ID that can be a number from 1  
to 1001. VLAN IDs 1002 to 1005 are reserved for Token Ring and FDDI VLANs. To create a  
normal-range VLAN to be added to the VLAN database, assign a number and name to the VLAN.  
Note  
When the switch is in VTP transparent mode, you can assign VLAN IDs greater than 1006, but they are  
not added to the VLAN database. See the “Configuring Extended-Range VLANs” section on  
page 12-11.  
For the list of default parameters that are assigned when you add a VLAN, see the “Configuring  
Normal-Range VLANs” section on page 12-4.  
Beginning in privileged EXEC mode, follow these steps to use config-vlan mode to create or modify an  
Ethernet VLAN:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
vlan vlan-id  
Enter a VLAN ID, and enter config-vlan mode. Enter a new VLAN ID  
to create a VLAN, or enter an existing VLAN ID to modify a VLAN.  
Note  
The available VLAN ID range for this command is 1 to 4094.  
For information about adding VLAN IDs greater than 1005  
(extended-range VLANs), see the “Configuring  
Extended-Range VLANs” section on page 12-11.  
Step 3  
name vlan-name  
(Optional) Enter a name for the VLAN. If no name is entered, the default  
is to append the vlan-id with leading zeros to the word VLAN. For  
example, VLAN0004 is a default VLAN name for VLAN 4.  
Step 4  
Step 5  
Step 6  
Step 7  
mtu mtu-size  
(Optional) Change the MTU size (or other VLAN characteristic).  
Return to privileged EXEC mode.  
end  
show vlan {name vlan-name | id vlan-id} Verify your entries.  
copy running-config startup config (Optional) If the switch is in VTP transparent mode, the VLAN  
configuration is saved in the running configuration file as well as in the  
VLAN database. This saves the configuration in the switch startup  
configuration file.  
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Chapter 12 Configuring VLANs  
Configuring Normal-Range VLANs  
To return the VLAN name to the default settings, use the no vlan name, no vlan mtu, or no remote  
span config-vlan commands.  
This example shows how to use config-vlan mode to create Ethernet VLAN 20, name it test20, and add  
it to the VLAN database:  
Switch# configure terminal  
Switch(config)# vlan 20  
Switch(config-vlan)# name test20  
Switch(config-vlan)# end  
Beginning in privileged EXEC mode, follow these steps to use VLAN configuration mode to create or  
modify an Ethernet VLAN:  
Command  
Purpose  
Step 1  
Step 2  
vlan database  
Enter VLAN database configuration mode.  
vlan vlan-id name vlan-name  
Add an Ethernet VLAN by assigning a number to it. The range is 1 to  
1001; do not enter leading zeros.  
If no name is entered, the default is to append the vlan-id with leading  
zeros to the word VLAN. For example, VLAN0004 is a default VLAN  
name for VLAN 4.  
Step 3  
Step 4  
vlan vlan-id mtu mtu-size  
(Optional) To modify a VLAN, identify the VLAN and change a  
characteristic, such as the MTU size.  
exit  
Update the VLAN database, propagate it throughout the administrative  
domain, and return to privileged EXEC mode.  
Step 5  
Step 6  
show vlan {name vlan-name | id vlan-id} Verify your entries.  
copy running-config startup config (Optional) If the switch is in VTP transparent mode, the VLAN  
configuration is saved in the running configuration file as well as in the  
VLAN database. This saves the configuration in the switch startup  
configuration file.  
Note  
You cannot configure an RSPAN VLAN in VLAN database configuration mode.  
To return the VLAN name to the default settings, use the no vlan vlan-id name VLAN configuration  
command.  
This example shows how to use VLAN database configuration mode to create Ethernet VLAN 20, name  
it test20, and add it to the VLAN database:  
Switch# vlan database  
Switch(vlan)# vlan 20 name test20  
Switch(vlan)# exit  
APPLY completed.  
Exiting....  
Switch#  
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Chapter 12 Configuring VLANs  
Configuring Normal-Range VLANs  
Deleting a VLAN  
When you delete a VLAN from a switch that is in VTP server mode, the VLAN is removed from the  
VLAN database for all switches in the VTP domain. When you delete a VLAN from a switch that is in  
VTP transparent mode, the VLAN is deleted only on that specific switch.  
You cannot delete the default VLANs for the different media types: Ethernet VLAN 1 and FDDI or  
Token Ring VLANs 1002 to 1005.  
Caution  
When you delete a VLAN, any ports assigned to that VLAN become inactive. They remain associated  
with the VLAN (and thus inactive) until you assign them to a new VLAN.  
Beginning in privileged EXEC mode, follow these steps to delete a VLAN on the switch by using global  
configuration mode:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
Step 5  
configure terminal  
no vlan vlan-id  
Enter global configuration mode.  
Remove the VLAN by entering the VLAN ID.  
Return to privileged EXEC mode.  
Verify the VLAN removal.  
end  
show vlan brief  
copy running-config startup config  
(Optional) If the switch is in VTP transparent mode, the VLAN  
configuration is saved in the running configuration file as well as in  
the VLAN database. This saves the configuration in the switch startup  
configuration file.  
To delete a VLAN in VLAN database configuration mode, use the vlan database privileged EXEC  
command to enter VLAN database configuration mode and the no vlan vlan-id VLAN configuration  
command.  
Assigning Static-Access Ports to a VLAN  
You can assign a static-access port to a VLAN without having VTP globally propagate VLAN  
configuration information by disabling VTP (VTP transparent mode).  
Note  
If you assign an interface to a VLAN that does not exist, the new VLAN is created. (See the “Creating  
or Modifying an Ethernet VLAN” section on page 12-8.)  
Beginning in privileged EXEC mode, follow these steps to assign a port to a VLAN in the VLAN  
database:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
Enter global configuration mode  
interface interface-id  
switchport mode access  
Enter the interface to be added to the VLAN.  
Define the VLAN membership mode for the port (Layer 2 access  
port).  
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Chapter 12 Configuring VLANs  
Configuring Extended-Range VLANs  
Command  
Purpose  
Step 4  
switchport access vlan vlan-id  
Assign the port to a VLAN. Valid VLAN IDs are 1 to 4094.  
Return to privileged EXEC mode.  
Step 5  
Step 6  
Step 7  
end  
show running-config interface interface-id Verify the VLAN membership mode of the interface.  
show interfaces interface-id switchport  
Verify your entries in the Administrative Mode and the Access Mode  
VLAN fields of the display.  
Step 8  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return an interface to its default configuration, use the default interface interface-id interface  
configuration command.  
This example shows how to configure a port as an access port in VLAN 2:  
Switch# configure terminal  
Enter configuration commands, one per line. End with CNTL/Z.  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# switchport mode access  
Switch(config-if)# switchport access vlan 2  
Switch(config-if)# end  
Switch#  
Configuring Extended-Range VLANs  
When the switch is in VTP transparent mode (VTP disabled), you can create extended-range VLANs (in  
the range 1006 to 4094 for any switch port commands that allow VLAN IDs). Enter the vlan vlan-id  
global configuration command to access config-vlan mode and to configure extended-range VLANs.  
The VLAN database configuration mode (that you access by entering the vlan database privileged  
EXEC command) does not support the extended range.  
Extended-range VLAN configurations are not stored in the VLAN database. Because VTP mode is  
transparent, they are stored in the switch running configuration file. You can save the configuration in  
the startup configuration file by using the copy running-config startup-config privileged EXEC  
command.  
Note  
Although the switch supports 4094 VLAN IDs, see the “Supported VLANs” section on page 12-2 for  
the actual number of VLANs supported.  
This section includes this information about extended-range VLANs:  
•
•
•
•
Default VLAN Configuration, page 12-12  
Extended-Range VLAN Configuration Guidelines, page 12-12  
Creating an Extended-Range VLAN, page 12-12  
Displaying VLANs, page 12-13  
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Chapter 12 Configuring VLANs  
Configuring Extended-Range VLANs  
Default VLAN Configuration  
See Table 12-2 on page 12-7 for the default configuration for Ethernet VLANs. You can change only the  
MTU size on extended-range VLANs; all other characteristics must remain at the default state.  
Extended-Range VLAN Configuration Guidelines  
Follow these guidelines when creating extended-range VLANs:  
•
To add an extended-range VLAN, you must use the vlan vlan-id global configuration command and  
access config-vlan mode. You cannot add extended-range VLANs in VLAN database configuration  
mode (accessed by entering the vlan database privileged EXEC command).  
•
VLAN IDs in the extended range are not saved in the VLAN database and are not recognized by  
VTP.  
•
•
You cannot include extended-range VLANs in the pruning eligible range.  
The switch must be in VTP transparent mode when you create extended-range VLANs. If VTP mode  
is server or client, an error message is generated, and the extended-range VLAN is rejected.  
•
You can set the VTP mode to transparent in global configuration mode or in VLAN database  
configuration mode. See the “Disabling VTP (VTP Transparent Mode)” section on page 13-11. You  
should save this configuration to the startup configuration so that the switch will boot up in VTP  
transparent mode. Otherwise, you will lose extended-range VLAN configuration if the switch resets.  
•
•
VLANs in the extended range are not supported by VQP. They cannot be configured by VMPS.  
STP is enabled by default on extended-range VLANs, but you can disable it by using the no  
spanning-tree vlan vlan-id global configuration command. When the maximum number of  
spanning-tree instances (64) are on the switch, spanning tree is disabled on any newly created  
VLANs. If the number of VLANs on the switch exceeds the maximum number of spanning tree  
instances, we recommend that you configure the IEEE 802.1S Multiple STP (MSTP) on your switch  
to map multiple VLANs to a single STP instance. For more information about MSTP, see  
Chapter 10, “Configuring MSTP.”  
Creating an Extended-Range VLAN  
You create an extended-range VLAN in global configuration mode by entering the vlan global  
configuration command with a VLAN ID from 1006 to 4094. This command accesses the config-vlan  
mode. The extended-range VLAN has the default Ethernet VLAN characteristics (see Table 12-2), and  
the MTU size is the only parameter you can change. See the description of the vlan global configuration  
command in the command reference for defaults of all parameters. If you enter an extended-range VLAN  
ID when the switch is not in VTP transparent mode, an error message is generated when you exit from  
config-vlan mode, and the extended-range VLAN is not created.  
Extended-range VLANs are not saved in the VLAN database; they are saved in the switch running  
configuration file. You can save the extended-range VLAN configuration in the switch startup  
configuration file by using the copy running-config startup-config privileged EXEC command.  
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Chapter 12 Configuring VLANs  
Displaying VLANs  
Beginning in privileged EXEC mode, follow these steps to create an extended-range VLAN:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
vtp mode transparent  
vlan vlan-id  
Enter global configuration mode.  
Configure the switch for VTP transparent mode, disabling VTP.  
Enter an extended-range VLAN ID and enter config-vlan mode. The  
range is 1006 to 4094.  
Step 4  
mtu mtu-size  
(Optional) Modify the VLAN by changing the MTU size.  
Note  
Although all commands appear in the CLI help in config-vlan  
mode, only the mtu mtu-size command is supported for  
extended-range VLANs.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
show vlan id vlan-id  
Verify that the VLAN has been created.  
copy running-config startup config  
Save your entries in the switch startup configuration file. To save  
extended-range VLAN configurations, you need to save the VTP  
transparent mode configuration and the extended-range VLAN  
configuration in the switch startup configuration file. Otherwise, if the  
switch resets, it will default to VTP server mode, and the extended-range  
VLAN IDs will not be saved.  
To delete an extended-range VLAN, use the no vlan vlan-id global configuration command.  
The procedure for assigning static-access ports to an extended-range VLAN is the same as for  
normal-range VLANs. See the “Assigning Static-Access Ports to a VLAN” section on page 12-10.  
This example shows how to create a new extended-range VLAN with all default characteristics, enter  
config-vlan mode, and save the new VLAN in the switch startup configuration file:  
Switch(config)# vtp mode transparent  
Switch(config)# vlan 2000  
Switch(config-vlan)# end  
Switch# copy running-config startup config  
Displaying VLANs  
Use the show vlan privileged EXEC command to display a list of all VLANs on the switch, including  
extended-range VLANs. The display includes VLAN status, ports, and configuration information. To  
view normal-range VLANs in the VLAN database (1 to 1005) use the show VLAN configuration  
command (accessed by entering the vlan database privileged EXEC command). For a list of the VLAN  
IDs on the switch, use the show running-config vlan privileged EXEC command, optionally entering a  
VLAN ID range.  
Table 12-3 lists the commands for monitoring VLANs.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Table 12-3  
VLAN Monitoring Commands  
Command  
Command Mode  
Purpose  
show  
VLAN configuration Display status of VLANs in the VLAN database.  
show current [vlan-id]  
VLAN configuration Display status of all or the specified VLAN in the  
VLAN database.  
show interfaces [vlan  
vlan-id]  
Privileged EXEC  
Display characteristics for all interfaces or for  
the specified VLAN configured on the switch.  
show running-config vlan Privileged EXEC  
show vlan [id vlan-id] Privileged EXEC  
Display all or a range of VLANs on the switch.  
Display parameters for all VLANs or the  
specified VLAN on the switch.  
For more details about the show command options and explanations of output fields, see the command  
reference for this release.  
Configuring VLAN Trunks  
These sections describe how VLAN trunks function on the switch:  
•
•
•
Trunking Overview, page 12-14  
IEEE 802.1Q Configuration Considerations, page 12-16  
Default Layer 2 Ethernet Interface VLAN Configuration, page 12-17  
Trunking Overview  
A trunk is a point-to-point link between one or more Ethernet switch interfaces and another networking device  
such as a router or a switch. Gigabit Ethernet trunks carry the traffic of multiple VLANs over a single link,  
and you can extend the VLANs across an entire network.  
The switch supports IEEE 802.1Q, the industry-standard trunking encapsulation.  
Figure 12-2 shows a network of switches that are connected by IEEE 802.1Q trunks.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Figure 12-2  
Switches in an IEEE 802.1Q Trunking Environment  
Catalyst 6000 series  
switch  
802.1Q  
trunk  
802.1Q  
trunk  
Catalyst  
3500 XL  
switch  
BladeCenter  
Catalyst  
3500 XL  
BladeCenter  
switch  
VLAN1  
VLAN3  
VLAN2  
VLAN2  
VLAN1  
VLAN3  
You can configure a trunk on a single Ethernet interface or on an EtherChannel bundle. For more  
information about EtherChannel, see Chapter 24, “Configuring EtherChannels and Layer 2 Trunk  
Failover.”  
Ethernet trunk interfaces support different trunking modes (see Table 12-4). You can set an interface as  
trunking or nontrunking or to negotiate trunking with the neighboring interface. To autonegotiate  
trunking, the interfaces must be in the same VTP domain.  
Trunk negotiation is managed by the Dynamic Trunking Protocol (DTP), which is a Point-to-Point  
Protocol. However, some internetworking devices might forward DTP frames improperly, which could  
cause misconfigurations.  
To avoid this, you should configure interfaces connected to devices that do not support DTP to not  
forward DTP frames, that is, to turn off DTP.  
•
If you do not intend to trunk across those links, use the switchport mode access interface  
configuration command to disable trunking.  
•
To enable trunking to a device that does not support DTP, use the switchport mode trunk and  
switchport nonegotiate interface configuration commands to cause the interface to become a trunk  
but to not generate DTP frames.  
Table 12-4  
Layer 2 Interface Modes  
Mode  
Function  
switchport mode access  
Puts the interface (access port) into permanent nontrunking mode. The interface becomes  
a nontrunk interface even if the neighboring interface is a trunk interface.  
switchport mode dynamic  
desirable  
Makes the interface actively attempt to convert the link to a trunk link. The interface  
becomes a trunk interface if the neighboring interface is set to trunk, desirable, or auto  
mode. The default switch-port mode for all Ethernet interfaces is dynamic desirable.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Table 12-4  
Mode  
Layer 2 Interface Modes (continued)  
Function  
switchport mode dynamic auto Makes the interface able to convert the link to a trunk link. The interface becomes a trunk  
interface if the neighboring interface is set to trunk or desirable mode.  
switchport mode trunk  
Puts the interface into permanent trunking mode and negotiates to convert the link into a  
trunk link. The interface becomes a trunk interface even if the neighboring interface is  
not a trunk interface.  
switchport nonegotiate  
Prevents the interface from generating DTP frames. You can use this command only when  
the interface switchport mode is access or trunk. You must manually configure the  
neighboring interface as a trunk interface to establish a trunk link.  
IEEE 802.1Q Configuration Considerations  
IEEE 802.1Q trunks impose these limitations on a network:  
•
In a network of Cisco switches connected through IEEE 802.1Q trunks, the switches maintain one  
instance of spanning tree for each VLAN allowed on the trunks. Non-Cisco devices might support  
one spanning-tree instance for all VLANs.  
When you connect a Cisco switch to a non-Cisco device through an IEEE 802.1Q trunk, the Cisco  
switch combines the spanning-tree instance of the VLAN of the trunk with the spanning-tree  
instance of the non-Cisco IEEE 802.1Q switch. However, spanning-tree information for each VLAN  
is maintained by Cisco switches separated by a cloud of non-Cisco IEEE 802.1Q switches. The  
non-Cisco IEEE 802.1Q cloud separating the Cisco switches is treated as a single trunk link between  
the switches.  
•
•
Make sure the native VLAN for an IEEE 802.1Q trunk is the same on both ends of the trunk link. If  
the native VLAN on one end of the trunk is different from the native VLAN on the other end,  
spanning-tree loops might result.  
Disabling spanning tree on the native VLAN of an IEEE 802.1Q trunk without disabling spanning  
tree on every VLAN in the network can potentially cause spanning-tree loops. We recommend that  
you leave spanning tree enabled on the native VLAN of an IEEE 802.1Q trunk or disable spanning  
tree on every VLAN in the network. Make sure your network is loop-free before disabling spanning  
tree.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Default Layer 2 Ethernet Interface VLAN Configuration  
Table 12-5 shows the default Layer 2 Ethernet interface VLAN configuration.  
Table 12-5  
Default Layer 2 Ethernet Interface VLAN Configuration  
Feature  
Default Setting  
Interface mode  
trunk on the internal ports (ports 1 to 16).  
dynamic desirable on the external ports (ports 17  
to 20).  
Allowed VLAN range  
VLANs 1 to 4094.VLAN ID range is 2 to 4094 on  
the internal 1000 Mbps ports (ports 1 to 14).  
VLAN ID range is 1 on the internal 100 Mbps  
management module ports (ports 15 to 16).  
VLAN ID range is 1 to 4094 on the external ports  
(ports 17 to 20).  
VLAN range eligible for pruning  
VLANs 2 to 1001  
VLAN 1  
Default VLAN (for internal 100 Mbps  
management module ports)  
Default VLAN (for external ports and  
internal 1000 Mbps ports)  
VLAN 2  
Native VLAN (for IEEE 802.1Q trunks) VLAN 1 (for internal 100 Mbps management  
module ports)  
VLAN 2 (for external ports and internal 1000 Mbps  
ports)  
Configuring an Ethernet Interface as a Trunk Port  
Because trunk ports send and receive VTP advertisements, to use VTP you must ensure that at least one  
trunk port is configured on the switch and is connected to the trunk port of a second switch. Otherwise,  
the switch cannot receive any VTP advertisements.  
This section includes these procedures for configuring an Ethernet interface as a trunk port on the switch:  
•
•
•
•
Interaction with Other Features, page 12-18  
Defining the Allowed VLANs on a Trunk, page 12-19  
Changing the Pruning-Eligible List, page 12-20  
Configuring the Native VLAN for Untagged Traffic, page 12-21  
Note  
The default mode for external interfaces is switchport mode dynamic desirable interface configuration  
mode. If the neighboring interface supports trunking and is configured to allow trunking, the link is a  
Layer 2 trunk.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Interaction with Other Features  
Trunking interacts with other features in these ways:  
•
Trunk ports can be grouped into EtherChannel port groups, but all trunks in the group must have the  
same configuration. When a group is first created, all ports follow the parameters set for the first  
port to be added to the group. If you change the configuration of one of these parameters, the switch  
propagates that setting to all ports in the group:  
–
–
–
–
allowed-VLAN list  
STP port priority for each VLAN  
STP Port Fast setting  
trunk status (If one port in a port group ceases to be a trunk, all ports cease to be trunks.)  
•
•
•
If you try to enable IEEE 802.1X on a trunk port, an error message appears, and IEEE 802.1X is not  
enabled. If you try to change the mode of an IEEE 802.1X-enabled port to trunk, the port mode is  
not changed.  
A port in dynamic mode can negotiate with its neighbor to become a trunk port. If you try to enable  
IEEE 802.1X on a dynamic port, an error message appears, and IEEE 802.1X is not enabled. If you  
try to change the mode of an IEEE 802.1X-enabled port to dynamic, the port mode is not changed.  
Protected ports are supported on IEEE 802.1Q trunks.  
Configuring a Trunk Port  
Beginning in privileged EXEC mode, follow these steps to configure a port as an IEEE 802.1Q  
trunk port:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Enter the interface configuration mode and the port to be configured for  
trunking.  
Step 3  
switchport mode {dynamic {auto |  
desirable} | trunk}  
Configure the interface as a Layer 2 trunk (required only if the interface  
is a Layer 2 access port or to specify the trunking mode).  
•
•
•
dynamic auto—Set the interface to a trunk link if the neighboring  
interface is set to trunk or desirable mode.  
dynamic desirable—Set the interface to a trunk link if the  
neighboring interface is set to trunk, desirable, or auto mode.  
trunk—Set the interface in permanent trunking mode and negotiate  
to convert the link to a trunk link even if the neighboring interface is  
not a trunk interface.  
Step 4  
switchport access vlan vlan-id  
(Optional) Specify the default VLAN, which is used if the interface stops  
trunking.  
Step 5  
Step 6  
Step 7  
switchport trunk native vlan vlan-id  
Specify the native VLAN.  
end  
Return to privileged EXEC mode.  
show interfaces interface-id switchport Display the switchport configuration of the interface in the Administrative  
Mode and the Administrative Trunking Encapsulation fields of the  
display.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Command  
Purpose  
Step 8  
Step 9  
show interfaces interface-id trunk  
Display the trunk configuration of the interface.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return an interface to its default configuration, use the default interface interface-id interface  
configuration command. To reset all trunking characteristics of a trunking interface to the defaults, use  
the no switchport trunk interface configuration command. To disable trunking, use the switchport  
mode access interface configuration command to configure the port as a static-access port.  
This example shows how to configure a port as an IEEE 802.1Q trunk. The example assumes that the  
neighbor interface is configured to support IEEE 802.1Q trunking.  
Switch# configure terminal  
Enter configuration commands, one per line. End with CNTL/Z.  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# switchport mode dynamic desirable  
Switch(config-if)# end  
Defining the Allowed VLANs on a Trunk  
Note  
You cannot change the trunk mode on the internal interfaces connected to the 100 Mbps management  
module (ports 15 and 16). You also cannot remove the management VLAN from the allowed list.  
By default, a trunk port sends traffic to and receives traffic from all VLANs. All VLAN IDs are allowed  
on each trunk. However, you can remove VLANs from the allowed list, preventing traffic from those  
VLANs from passing over the trunk. To restrict the traffic a trunk carries, use the switchport trunk  
allowed vlan remove vlan-list interface configuration command to remove specific VLANs from the  
allowed list.  
To reduce the risk of spanning-tree loops or storms, you can disable VLAN 1 on any individual VLAN  
trunk port by removing VLAN 1 from the allowed list. This is known as VLAN 1 minimization. VLAN 1  
minimization disables VLAN 1 (the default VLAN on all Cisco switch trunk ports) on an individual  
VLAN trunk link. As a result, no user traffic, including spanning-tree advertisements, is sent or received  
on VLAN 1.  
When you remove VLAN 1 from a trunk port, the interface continues to send and receive management  
traffic, for example, Cisco Discovery Protocol (CDP), Port Aggregation Protocol (PAgP), Link  
Aggregation Control Protocol (LACP), Dynamic Trunking Protocol (DTP), and VLAN Trunking  
Protocol (VTP) in VLAN 1.  
If a trunk port with VLAN 1 disabled is converted to a nontrunk port, it is added to the access VLAN.  
If the access VLAN is set to 1, the port is added to VLAN 1, regardless of the switchport trunk allowed  
setting. The same is true for any VLAN that has been disabled on the port.  
A trunk port can become a member of a VLAN if the VLAN is enabled, if VTP knows of the VLAN,  
and if the VLAN is in the allowed list for the port. When VTP detects a newly enabled VLAN and the  
VLAN is in the allowed list for a trunk port, the trunk port automatically becomes a member of the  
enabled VLAN. When VTP detects a new VLAN and the VLAN is not in the allowed list for a trunk  
port, the trunk port does not become a member of the new VLAN.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Beginning in privileged EXEC mode, follow these steps to modify the allowed list of an IEEE  
802.1Q trunk:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
configure terminal  
Enter global configuration mode.  
interface interface-id  
switchport mode trunk  
Enter interface configuration mode and the port to be configured.  
Configure the interface as a VLAN trunk port.  
(Optional) Configure the list of VLANs allowed on the trunk.  
switchport trunk allowed vlan {add |  
all | except | remove} vlan-list  
For explanations about using the add, all, except, and remove keywords,  
see the command reference for this release.  
The vlan-list parameter is either a single VLAN number from 1 to 4094  
or a range of VLANs described by two VLAN numbers, the lower one  
first, separated by a hyphen. Do not enter any spaces between  
comma-separated VLAN parameters or in hyphen-specified ranges.  
All VLANs are allowed by default.  
Return to privileged EXEC mode.  
Step 5  
Step 6  
Step 7  
end  
show interfaces interface-id switchport Verify your entries in the Trunking VLANs Enabled field of the display.  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To return to the default allowed VLAN list of all VLANs, use the no switchport trunk allowed vlan  
interface configuration command.  
This example shows how to remove VLAN 2 from the allowed VLAN list:  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# switchport trunk allowed vlan remove 2  
Switch(config-if)# end  
Switch#  
Changing the Pruning-Eligible List  
The pruning-eligible list applies only to trunk ports. Each trunk port has its own eligibility list. VTP  
pruning must be enabled for this procedure to take effect. The “Enabling VTP Pruning” section on  
page 13-13 describes how to enable VTP pruning.  
Beginning in privileged EXEC mode, follow these steps to remove VLANs from the pruning-eligible  
list on a trunk port:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Enter interface configuration mode, and select the trunk port for which  
VLANs should be pruned.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Command  
Purpose  
Step 3  
switchport trunk pruning vlan {add | Configure the list of VLANs allowed to be pruned from the trunk. (See  
except | none | remove} vlan-list  
[,vlan[,vlan[,,,]]  
the “VTP Pruning” section on page 13-4).  
For explanations about using the add, except, none, and remove  
keywords, see the command reference for this release.  
Separate nonconsecutive VLAN IDs with a comma and no spaces; use a  
hyphen to designate a range of IDs. Valid IDs are from 2 to 1001.  
Extended-range VLANs (VLAN IDs 1006 to 4094) cannot be pruned.  
VLANs that are pruning-ineligible receive flooded traffic.  
The default list of VLANs allowed to be pruned contains VLANs 2 to  
1001.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show interfaces interface-id switchport Verify your entries in the Pruning VLANs Enabled field of the display.  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To return to the default pruning-eligible list of all VLANs, use the no switchport trunk pruning vlan  
interface configuration command.  
Configuring the Native VLAN for Untagged Traffic  
A trunk port configured with IEEE 802.1Q tagging can receive both tagged and untagged traffic. By  
default, the switch forwards untagged traffic in the native VLAN configured for the port. The native  
VLAN is VLAN 1 by default.  
Note  
The native VLAN can be assigned any VLAN ID; it is not dependent on the management VLAN. The  
native VLAN ID on the internal 100 Mbps management module interfaces (ports 15 and 16) changes  
when the management VLAN changes. The native VLAN cannot be explicitly changed, it will only  
change when the management VLAN of the switch changes. Changing the native VALN on management  
module interfaces is not allowed. This ensures that the switch and the management module always have  
an open communication path for ethernet traffic used to manage the switch.  
For information about IEEE 802.1Q configuration issues, see the “IEEE 802.1Q Configuration  
Considerations” section on page 12-16.  
Beginning in privileged EXEC mode, follow these steps to configure the native VLAN on an IEEE  
802.1Q trunk:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Enter interface configuration mode, and define the interface that is  
configured as the IEEE 802.1Q trunk.  
Step 3  
Step 4  
switchport trunk native vlan vlan-id  
Configure the VLAN that is sending and receiving untagged traffic  
on the trunk port.  
For vlan-id, the range is 1 to 4094.  
end  
Return to privileged EXEC mode.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Command  
Purpose  
Step 5  
Step 6  
show interfaces interface-id switchport  
Verify your entries in the Trunking Native Mode VLAN field.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return to the default native VLAN, VLAN 1, use the no switchport trunk native vlan interface  
configuration command.  
If a packet has a VLAN ID that is the same as the outgoing port native VLAN ID, the packet is sent  
untagged; otherwise, the switch sends the packet with a tag.  
Load Sharing Using STP  
Load sharing divides the bandwidth supplied by parallel trunks connecting switches. To avoid loops,  
STP normally blocks all but one parallel link between switches. Using load sharing, you divide the  
traffic between the links according to which VLAN the traffic belongs.  
You configure load sharing on trunk ports by using STP port priorities or STP path costs. For load  
sharing using STP port priorities, both load-sharing links must be connected to the same switch. For load  
sharing using STP path costs, each load-sharing link can be connected to the same switch or to two  
different switches. For more information about STP, see Chapter 9, “Configuring STP.”  
Load Sharing Using STP Port Priorities  
When two ports on the same switch form a loop, the STP port priority setting determines which port is  
enabled and which port is in a blocking state. You can set the priorities on a parallel trunk port so that  
the port carries all the traffic for a given VLAN. The trunk port with the higher priority (lower values)  
for a VLAN is forwarding traffic for that VLAN. The trunk port with the lower priority (higher values)  
for the same VLAN remains in a blocking state for that VLAN. One trunk port sends or receives all  
traffic for the VLAN.  
Figure 12-3 shows two trunks connecting supported switches. In this example, the switches are  
configured as follows:  
•
•
•
•
VLANs 8 through 10 are assigned a port priority of 16 on Trunk 1.  
VLANs 3 through 6 retain the default port priority of 128 on Trunk 1.  
VLANs 3 through 6 are assigned a port priority of 16 on Trunk 2.  
VLANs 8 through 10 retain the default port priority of 128 on Trunk 2.  
In this way, Trunk 1 carries traffic for VLANs 8 through 10, and Trunk 2 carries traffic for VLANs 3  
through 6. If the active trunk fails, the trunk with the lower priority takes over and carries the traffic for  
all of the VLANs. No duplication of traffic occurs over any trunk port.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Figure 12-3  
Load Sharing by Using STP Port Priorities  
Switch 1  
Trunk 2  
Trunk 1  
VLANs 3 – 6 (priority 10)  
VLANs 8 – 10 (priority 128)  
VLANs 8 – 10 (priority 10)  
VLANs 3 – 6 (priority 128)  
BladeCenter  
Beginning in privileged EXEC mode, follow these steps to configure the network shown in Figure 12-3.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode on Switch 1.  
Configure a VTP administrative domain.  
vtp domain domain-name  
The domain name can be from 1 to 32 characters.  
Configure Switch 1 as the VTP server.  
Step 3  
Step 4  
Step 5  
vtp mode server  
end  
Return to privileged EXEC mode.  
show vtp status  
Verify the VTP configuration on both Switch A and Switch B.  
In the display, check the VTP Operating Mode and the VTP Domain  
Name fields.  
Step 6  
Step 7  
Step 8  
show vlan  
Verify that the VLANs exist in the database on Switch A.  
Enter global configuration mode.  
configure terminal  
interface gigabitethernet0/17  
Enter interface configuration mode, and define Gigabit Ethernet  
port 0/17 as the interface to be configured as a trunk.  
Step 9  
switchport mode trunk  
end  
Configure the port as a trunk port.  
Return to privilege EXEC mode.  
Verify the VLAN configuration.  
Step 10  
Step 11  
show interfaces gigabitethernet0/17  
switchport  
Step 12  
Step 13  
Repeat Steps 7 through 11 on Switch A for Gigabit Ethernet port 0/18.  
Repeat Steps 7 through 11 on Switch B to configure the trunk ports on  
Gigabit Ethernet ports 0/17 and 0/18.  
Step 14  
show vlan  
When the trunk links come up, VTP passes the VTP and VLAN  
information to Switch B. Verify that Switch B has learned the VLAN  
configuration.  
Step 15  
Step 16  
configure terminal  
Enter global configuration mode on Switch A.  
interface gigabitethernet0/17  
Enter interface configuration mode, and define the interface to set the  
STP port priority.  
Step 17  
Step 18  
spanning-tree vlan 8-10 port-priority 16 Assign the port priority of 16 for VLANs 8 through 10.  
spanning-tree vlan 10 port-priority 16 Assign the port priority of 16 for VLAN 10.  
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Chapter 12 Configuring VLANs  
Configuring VLAN Trunks  
Command  
Purpose  
Step 19  
exit  
Return to global configuration mode.  
Step 20  
interface gigabitethernet0/18  
Enter interface configuration mode, and define the interface to set the  
STP port priority.  
Step 21  
Step 22  
Step 23  
Step 24  
spanning-tree vlan 3-6 port-priority 16  
end  
Assign the port priority of 16 for VLANs 3 through 6.  
Return to privileged EXEC mode.  
show running-config  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Load Sharing Using STP Path Cost  
You can configure parallel trunks to share VLAN traffic by setting different path costs on a trunk and  
associating the path costs with different sets of VLANs. The VLANs keep the traffic separate. Because  
no loops exist, STP does not disable the ports, and redundancy is maintained in the event of a lost link.  
In Figure 12-4, Trunk ports 1 and 2 are 1000BASE-T ports. The path costs for the VLANs are assigned  
as follows:  
•
•
•
•
VLANs 2 through 4 are assigned a path cost of 30 on Trunk port 1.  
VLANs 8 through 10 retain the default 1000BASE-T path cost on Trunk port 1 of 19.  
VLANs 8 through 10 are assigned a path cost of 30 on Trunk port 2.  
VLANs 2 through 4 retain the default 1000BASE-T path cost on Trunk port 2 of 19.  
Figure 12-4  
Load-Sharing Trunks with Traffic Distributed by Path Cost  
Switch 1  
Trunk port 1  
Trunk port 2  
VLANs 2 – 4 (path cost 30)  
VLANs 8 – 10 (path cost 19)  
VLANs 8 – 10 (path cost 30)  
VLANs 2 – 4 (path cost 19)  
BladeCenter  
Beginning in privileged EXEC mode, follow these steps to configure the network shown in Figure 12-4:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode on Switch A.  
interface gigabitethernet0/17  
Enter interface configuration mode, and define Gigabit Ethernet  
port 0/17 as the interface to be configured as a trunk.  
Step 3  
switchport mode trunk  
Configure the port as a trunk port.  
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Chapter 12 Configuring VLANs  
Configuring VMPS  
Command  
Purpose  
Step 4  
exit  
Return to global configuration mode.  
Step 5  
Repeat Steps 2 through 4 on Switch A interface Gigabit Ethernet  
port 0/18.  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
In the display, make sure that interfaces Gigabit Ethernet ports 0/17 and  
0/18 are configured as trunk ports.  
Step 8  
show vlan  
When the trunk links come up, Switch A receives the VTP information  
from the other switches. Verify that Switch A has learned the VLAN  
configuration.  
Step 9  
configure terminal  
Enter global configuration mode.  
Step 10  
interface gigabitethernet0/17  
Enter interface configuration mode, and define Gigabit Ethernet  
port 0/17 as the interface to set the STP cost.  
Step 11  
Step 12  
Step 13  
spanning-tree vlan 2-4 cost 30  
end  
Set the spanning-tree path cost to 30 for VLANs 2 through 4.  
Return to global configuration mode.  
Repeat Steps 9 through 11 on Switch A interface Gigabit Ethernet  
ports 0/18, and set the spanning-tree path cost to 30 for VLANs 8, 9, and  
10.  
Step 14  
Step 15  
exit  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
In the display, verify that the path costs are set correctly for interfaces  
Gigabit Ethernet ports 0/17 and 0/18.  
Step 16  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Configuring VMPS  
The switch cannot be a VMPS server but can act as a client to the VMPS and communicate with it  
through the VLAN Query Protocol (VQP). VMPS dynamically assigns dynamic access port VLAN  
membership.  
This section includes this information about configuring VMPS:  
•
•
•
•
•
•
•
“Understanding VMPS” section on page 12-26  
“Default VMPS Client Configuration” section on page 12-27  
“VMPS Configuration Guidelines” section on page 12-27  
“Configuring the VMPS Client” section on page 12-28  
“Monitoring the VMPS” section on page 12-30  
“Troubleshooting Dynamic Port VLAN Membership” section on page 12-31  
“VMPS Configuration Example” section on page 12-31  
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Chapter 12 Configuring VLANs  
Configuring VMPS  
Understanding VMPS  
When the VMPS receives a VQP request from a client switch, it searches its database for a  
MAC-address-to-VLAN mapping. The server response is based on this mapping and whether or not the  
server is in secure mode. Secure mode determines whether the server shuts down the port when a VLAN  
is not allowed on it or just denies the port access to the VLAN.  
In response to a request, the VMPS takes one of these actions:  
•
If the assigned VLAN is restricted to a group of ports, the VMPS verifies the requesting port against  
this group and responds as follows:  
–
–
If the VLAN is allowed on the port, the VMPS sends the VLAN name to the client in response.  
If the VLAN is not allowed on the port and the VMPS is not in secure mode, the VMPS sends  
an access-denied response.  
–
If the VLAN is not allowed on the port and the VMPS is in secure mode, the VMPS sends a  
port-shutdown response.  
•
If the VLAN in the database does not match the current VLAN on the port and active hosts exist on  
the port, the VMPS sends an access-denied or a port-shutdown response, depending on the secure  
mode of the VMPS.  
If the switch receives an access-denied response from the VMPS, it continues to block traffic from the  
MAC address to or from the port. The switch continues to monitor the packets directed to the port and  
sends a query to the VMPS when it identifies a new address. If the switch receives a port-shutdown  
response from the VMPS, it disables the port. The port must be manually re-enabled by using the device  
manager, CLI, CiscoWorks, or SNMP.  
You can also use an explicit entry in the configuration table to deny access to specific MAC addresses  
for security reasons. If you enter the none keyword for the VLAN name, the VMPS sends an  
access-denied or port-shutdown response, depending on the VMPS secure mode setting.  
Dynamic Port VLAN Membership  
A dynamic (nontrunking) port on the switch can belong to only one VLAN, with a VLAN ID from 1 to  
1005. When the link comes up, the switch does not forward traffic to or from this port until the VMPS  
provides the VLAN assignment. The VMPS receives the source MAC address from the first packet of a  
new host connected to the dynamic port and attempts to match the MAC address to a VLAN in the VMPS  
database.  
If there is a match, the VMPS sends the VLAN number for that port. If the client switch was not  
previously configured, it uses the domain name from the first VTP packet it receives on its trunk port  
from the VMPS. If the client switch was previously configured, it includes its domain name in the query  
packet to the VMPS to obtain its VLAN number. The VMPS verifies that the domain name in the packet  
matches its own domain name before accepting the request and responds to the client with the assigned  
VLAN number for the client. If there is no match, the VMPS either denies the request or shuts down the  
port (depending on the VMPS secure mode setting).  
Multiple hosts (MAC addresses) can be active on a dynamic port if they are all in the same VLAN;  
however, the VMPS shuts down a dynamic port if more than 20 hosts are active on the port.  
If the link goes down on a dynamic port, the port returns to an isolated state and does not belong to a  
VLAN. Any hosts that come online through the port are checked again through the VQP with the VMPS  
before the port is assigned to a VLAN.  
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Chapter 12 Configuring VLANs  
Configuring VMPS  
VMPS Database Configuration File  
The VMPS contains a database configuration file that you create. This ASCII text file is stored on a  
switch-accessible TFTP server that functions as a server for VMPS. The file contains VMPS  
information, such as the domain name, the fallback VLAN name, and the MAC-address-to-VLAN  
mapping. The switch cannot act as the VMPS, but you can use a Catalyst 5000 or Catalyst 6000 series  
switch as the VMPS.  
You can configure a fallback VLAN name. If you connect a device with a MAC address that is not in the  
database, the VMPS sends the fallback VLAN name to the client. If you do not configure a fallback  
VLAN and the MAC address does not exist in the database, the VMPS sends an access-denied response.  
If the VMPS is in secure mode, it sends a port-shutdown response.  
Whenever port names are used in the VMPS database configuration file, the server must use the switch  
convention for naming ports. For example, Gi0/17 is fixed Gigabit Ethernet port number 17.  
Default VMPS Client Configuration  
Table 12-6 shows the default VMPS and dynamic port configuration on client switches.  
Table 12-6  
Default VMPS Client and Dynamic Port Configuration  
Feature  
Default Setting  
VMPS domain server  
VMPS reconfirm interval  
VMPS server retry count  
Dynamic ports  
None  
60 minutes  
3
None configured  
VMPS Configuration Guidelines  
These guidelines and restrictions apply to dynamic access port VLAN membership:  
•
•
You should configure the VMPS before you configure ports as dynamic.  
When you configure a port as a dynamic access port, the spanning-tree Port Fast feature is  
automatically enabled for that port. The Port Fast mode accelerates the process of bringing the port  
into the forwarding state.  
•
•
IEEE 802.1X ports cannot be configured as dynamic access ports. If you try to enable IEEE 802.1X  
on a dynamic-access (VQP) port, an error message appears, and IEEE 802.1X is not enabled. If you  
try to change an IEEE 802.1X-enabled port to dynamic VLAN assignment, an error message  
appears, and the VLAN configuration is not changed.  
Trunk ports cannot be dynamic access ports, but you can enter the switchport access vlan dynamic  
interface configuration command for a trunk port. In this case, the switch retains the setting and  
applies it if the port is later configured as an access port.  
You must turn off trunking on the port before the dynamic access setting takes effect.  
Dynamic access ports cannot be network ports or monitor ports.  
•
•
Secure ports cannot be dynamic access ports. You must disable port security on a port before it  
becomes dynamic.  
•
Dynamic access ports cannot be members of an EtherChannel group.  
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Chapter 12 Configuring VLANs  
Configuring VMPS  
•
•
•
Port channels cannot be configured as dynamic access ports.  
The VTP management domain of the VMPS client and the VMPS server must be the same.  
VQP does not support extended-range VLANs (VLAN IDs higher than 1006). Extended-range  
VLANs cannot be configured by VMPS.  
•
The VLAN configured on the VMPS server should not be a voice VLAN.  
Configuring the VMPS Client  
You configure dynamic VLANs by using the VMPS (server). The switch can be a VMPS client; it cannot  
be a VMPS server.  
Entering the IP Address of the VMPS  
You must first enter the IP address of the server to configure the switch as a client.  
Beginning in privileged EXEC mode, follow these steps to enter the IP address of the VMPS:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
Enter global configuration mode.  
vmps server ipaddress primary  
vmps server ipaddress  
Enter the IP address of the switch acting as the primary VMPS server.  
Enter the IP address of the switch acting as a secondary VMPS server.  
You can enter up to three secondary server addresses.  
Return to privileged EXEC mode.  
Step 4  
Step 5  
Step 6  
end  
show vmps  
Verify your entries in the VMPS Domain Server field of the display.  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
Note  
The switch port that is connected to the VMPS server cannot be a dynamic access port. It can be either  
a static access port or a trunk port. See the “Configuring an Ethernet Interface as a Trunk Port” section  
on page 12-17.  
Configuring Dynamic Access Ports on VMPS Clients  
Caution  
Dynamic port VLAN membership is for end stations or hubs connected to end stations. Connecting  
dynamic access ports to other switches can cause a loss of connectivity.  
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Chapter 12 Configuring VLANs  
Configuring VMPS  
Beginning in privileged EXEC mode, follow these steps to configure a dynamic access port on a VMPS  
client switch:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Enter interface configuration mode and the switch port that is  
connected to the end station.  
Step 3  
Step 4  
switchport mode access  
Set the port to access mode.  
switchport access vlan dynamic  
Configure the port as eligible for dynamic VLAN membership.  
The dynamic access port must be connected to an end station.  
Return to privileged EXEC mode.  
Step 5  
Step 6  
Step 7  
end  
show interfaces interface-id switchport  
copy running-config startup-config  
Verify your entries in the Operational Mode field of the display.  
(Optional) Save your entries in the configuration file.  
To return an interface to its default configuration, use the default interface interface-id interface  
configuration command. To return an interface to its default switchport mode (dynamic desirable), use  
the no switchport mode interface configuration command. To reset the access mode to the default  
VLAN for the switch, use the no switchport access interface configuration command.  
Note  
When you configure a dynamic access port by using the switchport access vlan dynamic interface  
configuration command, the port might allow unauthorized users to access network resources if the  
interface changes from access mode to trunk mode through the DTP negotiation. The workaround is to  
configure the port as a static access port.  
Reconfirming VLAN Memberships  
Beginning in privileged EXEC mode, follow these steps to confirm the dynamic port VLAN membership  
assignments that the switch has received from the VMPS:  
Command  
Purpose  
Step 1  
Step 2  
vmps reconfirm  
show vmps  
Reconfirm dynamic port VLAN membership.  
Verify the dynamic VLAN reconfirmation status.  
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Chapter 12 Configuring VLANs  
Configuring VMPS  
Changing the Reconfirmation Interval  
VMPS clients periodically reconfirm the VLAN membership information received from the VMPS. You  
can set the number of minutes after which reconfirmation occurs.  
Beginning in privileged EXEC mode, follow these steps to change the reconfirmation interval:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
vmps reconfirm minutes  
Enter the number of minutes between reconfirmations of the dynamic  
VLAN membership.  
Enter a number from 1 to 120. The default is 60 minutes.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
end  
show vmps  
Verify the dynamic VLAN reconfirmation status in the Reconfirm  
Interval field of the display.  
Step 5  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default setting, use the no vmps reconfirm global configuration command.  
Changing the Retry Count  
Beginning in privileged EXEC mode, follow these steps to change the number of times that the switch  
attempts to contact the VMPS before querying the next server:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
vmps retry count  
Change the retry count.  
The retry range is from 1 to 10; the default is 3.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
Step 5  
end  
show vmps  
Verify your entry in the Server Retry Count field of the display.  
(Optional) Save your entries in the configuration file.  
copy running-config startup-config  
To return the switch to its default setting, use the no vmps retry global configuration command.  
Monitoring the VMPS  
You can display information about the VMPS by using the show vmps privileged EXEC command. The  
switch displays this information about the VMPS:  
VMPS VQP Version The version of VQP used to communicate with the VMPS. The switch queries  
the VMPS that is using VQP version 1.  
Reconfirm Interval  
The number of minutes the switch waits before reconfirming the  
VLAN-to-MAC-address assignments.  
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Configuring VMPS  
Server Retry Count  
The number of times VQP resends a query to the VMPS. If no response is  
received after this many tries, the switch starts to query the secondary VMPS.  
VMPS domain server The IP address of the configured VLAN membership policy servers. The switch  
sends queries to the one marked current. The one marked primary is the primary  
server.  
VMPS Action  
The result of the most recent reconfirmation attempt. A reconfirmation attempt  
can occur automatically when the reconfirmation interval expired, or you can  
force it by entering the vmps reconfirm privileged EXEC command or its  
CiscoWorks SNMP equivalent.  
This is an example of output for the show vmps privileged EXEC command:  
Switch# show vmps  
VQP Client Status:  
--------------------  
VMPS VQP Version:  
1
Reconfirm Interval: 60 min  
Server Retry Count: 3  
VMPS domain server: 172.20.128.86 (primary, current)  
172.20.128.87  
Reconfirmation status  
---------------------  
VMPS Action:  
No Dynamic Port  
Troubleshooting Dynamic Port VLAN Membership  
The VMPS shuts down a dynamic port under these conditions:  
•
The VMPS is in secure mode, and it does not allow the host to connect to the port. The VMPS shuts  
down the port to prevent the host from connecting to the network.  
•
More than 20 active hosts reside on a dynamic port.  
To re-enable a disabled dynamic port, enter the no shutdown interface configuration command.  
VMPS Configuration Example  
Figure 12-5 shows a network with a VMPS server switch and VMPS client switches with dynamic ports.  
In this example, these assumptions apply:  
•
•
•
•
•
The VMPS server and the VMPS client are separate switches.  
The Catalyst 6500 series Switch A is the primary VMPS server.  
The Catalyst 5000 series Switch C and Switch J are secondary VMPS servers.  
End stations are connected to the clients, Switch B and Switch I.  
The database configuration file is stored on the TFTP server with the IP address 172.20.22.7.  
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Chapter 12 Configuring VLANs  
Configuring VMPS  
Figure 12-5  
Dynamic Port VLAN Membership Configuration  
TFTP server  
Catalyst 5000 series  
Primary VMPS  
Router  
172.20.26.150  
Server 1  
Switch 1  
Switch 2  
Switch 3  
172.20.22.7  
Client  
172.20.26.151  
Dynamic-access port  
End  
station 1  
Trunk port  
Secondary VMPS  
Server 2  
172.20.26.152  
172.20.26.153  
172.20.26.154  
BladeCenter  
BladeCenter  
172.20.26.155  
172.20.26.156  
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C H A P T E R  
13  
Configuring VTP  
This chapter describes how to use the VLAN Trunking Protocol (VTP) and the VLAN database for  
managing VLANs on your Cisco Systems Intelligent Gigabit Ethernet Switch Module.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
The chapter includes these sections:  
•
•
•
Understanding VTP, page 13-1  
Configuring VTP, page 13-6  
Monitoring VTP, page 13-15  
Understanding VTP  
VTP is a Layer 2 messaging protocol that maintains VLAN configuration consistency by managing the  
addition, deletion, and renaming of VLANs on a network-wide basis. VTP minimizes misconfigurations  
and configuration inconsistencies that can cause several problems, such as duplicate VLAN names,  
incorrect VLAN-type specifications, and security violations.  
Before you create VLANs, you must decide whether to use VTP in your network. Using VTP, you can  
make configuration changes centrally on one or more switches and have those changes automatically  
communicated to all the other switches in the network. Without VTP, you cannot send information about  
VLANs to other switches. VTP configuration information is saved in the VTP VLAN database.  
VTP only learns about normal-range VLANs (VLAN IDs 1 to 1005). Extended-range VLANs (VLAN  
IDs greater than 1005) are not supported by VTP or stored in the VTP VLAN database.  
This section contains information about these VTP parameters:  
•
•
•
•
•
The VTP Domain, page 13-2  
VTP Modes, page 13-3  
VTP Advertisements, page 13-3  
VTP Version 2, page 13-4  
VTP Pruning, page 13-4  
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Chapter 13 Configuring VTP  
Understanding VTP  
The VTP Domain  
A VTP domain (also called a VLAN management domain) consists of one switch or several  
interconnected switches under the same administrative responsibility sharing the same VTP domain  
name. A switch can be in only one VTP domain.You can make global VLAN configuration changes for  
the domain.  
By default, the switch is in VTP no-management-domain state until it receives an advertisement for a  
domain over a trunk link (a link that carries the traffic of multiple VLANs) or until you configure a  
domain name. Until the management domain name is specified or learned, you cannot create or modify  
VLANs on a VTP server, and VLAN information is not propagated over the network.  
If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name  
and the VTP configuration revision number. The switch then ignores advertisements with a different  
domain name or an earlier configuration revision number.  
Caution  
Before adding a VTP client switch to a VTP domain, always verify that its VTP configuration revision  
number is lower than the configuration revision number of the other switches in the VTP domain.  
Switches in a VTP domain always use the VLAN configuration of the switch with the highest VTP  
configuration revision number. If you add a switch that has a revision number higher than the revision  
number in the VTP domain, it can erase all VLAN information from the VTP server and VTP domain.  
See the “Adding a VTP Client Switch to a VTP Domain” section on page 13-14 for the procedure for  
verifying and resetting the VTP configuration revision number.  
When you make a change to the VLAN configuration on a VTP server, the change is propagated to all  
switches in the VTP domain. VTP advertisements are sent over all IEEE 802.1Q trunk connections. VTP  
maps VLANs dynamically across multiple LAN types with unique names and internal index associates.  
Mapping eliminates excessive device administration required from network administrators.  
If you configure a switch for VTP transparent mode, you can create and modify VLANs, but the changes  
are not sent to other switches in the domain, and they affect only the individual switch. However,  
configuration changes made when the switch is in this mode are saved in the switch running  
configuration and can be saved to the switch startup configuration file.  
For domain name and password configuration guidelines, see the “VTP Configuration Guidelines”  
section on page 13-8.  
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Chapter 13 Configuring VTP  
Understanding VTP  
VTP Modes  
You can configure a supported switch to be in one of the VTP modes listed in Table 13-1.  
Table 13-1  
VTP Modes  
VTP Mode  
Description  
VTP server  
In VTP server mode, you can create, modify, and delete VLANs and specify other configuration parameters  
(such as the VTP version) for the entire VTP domain. VTP servers advertise their VLAN configurations to  
other switches in the same VTP domain and synchronize their VLAN configurations with other switches  
based on advertisements received over trunk links.  
In VTP server mode, VLAN configurations are saved in NVRAM. VTP server is the default mode.  
A VTP client behaves like a VTP server, but you cannot create, change, or delete VLANs on a VTP client.  
In VTP client mode, VLAN configurations are not saved in NVRAM.  
VTP client  
VTP transparent VTP transparent switches do not participate in VTP. A VTP transparent switch does not advertise its VLAN  
configuration and does not synchronize its VLAN configuration based on received advertisements.  
However, in VTP version 2, transparent switches do forward VTP advertisements that they receive from  
other switches from their trunk interfaces. You can create, modify, and delete VLANs on a switch in VTP  
transparent mode. The switch must be in VTP transparent mode when you create extended-range VLANs.  
See the “Configuring Extended-Range VLANs” section on page 12-11.  
When the switch is in VTP transparent mode, the VTP and VLAN configurations are saved in NVRAM,  
but they are not advertised to other switches. In this mode, VTP mode and domain name are saved in the  
switch running configuration and you can save this information in the switch startup configuration file by  
entering the copy running-config startup-config privileged EXEC command.  
When the network is configured with more than the maximum 250 VLANs, the switch automatically  
changes from VTP server or client mode to VTP transparent mode. The switch then operates with the  
VLAN configuration that preceded the one that sent it into transparent mode.  
VTP Advertisements  
Each switch in the VTP domain sends periodic global configuration advertisements from each trunk port  
to a reserved multicast address. Neighboring switches receive these advertisements and update their  
VTP and VLAN configurations as necessary.  
Note  
Because trunk ports send and receive VTP advertisements, you must ensure that at least one trunk port  
is configured on the switch and that this trunk port is connected to the trunk port of a second switch.  
Otherwise, the switch cannot receive any VTP advertisements. For more information on trunk ports, see  
the “Configuring VLAN Trunks” section on page 12-14.  
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Chapter 13 Configuring VTP  
Understanding VTP  
VTP advertisements distribute this global domain information:  
•
•
•
•
VTP domain name  
VTP configuration revision number  
Update identity and update timestamp  
MD5 digest VLAN configuration, including maximum transmission unit (MTU) size for each  
VLAN.  
•
Frame format  
VTP advertisements distribute this VLAN information for each configured VLAN:  
•
•
•
•
•
VLAN IDs  
VLAN name  
VLAN type  
VLAN state  
Additional VLAN configuration information specific to the VLAN type  
VTP Version 2  
If you use VTP in your network, you must decide whether to use version 1 or version 2. By default, VTP  
operates in version 1.  
VTP version 2 supports these features not supported in version 1:  
•
•
•
Token Ring support—VTP version 2 supports Token Ring Bridge Relay Function (TrBRF) and  
Token Ring Concentrator Relay Function (TrCRF) VLANs. For more information about Token  
Ring VLANs, see the “Configuring Normal-Range VLANs” section on page 12-4.  
Unrecognized Type-Length-Value (TLV) support—A VTP server or client propagates  
configuration changes to its other trunks, even for TLVs it is not able to parse. The unrecognized  
TLV is saved in NVRAM when the switch is operating in VTP server mode.  
Version-Dependent Transparent Mode—In VTP version 1, a VTP transparent switch inspects VTP  
messages for the domain name and version and forwards a message only if the version and domain  
name match. Because VTP version 2 supports only one domain, it forwards VTP messages in  
transparent mode without inspecting the version and domain name.  
•
Consistency Checks—In VTP version 2, VLAN consistency checks (such as VLAN names and  
values) are performed only when you enter new information through the CLI or SNMP. Consistency  
checks are not performed when new information is obtained from a VTP message or when  
information is read from NVRAM. If the MD5 digest on a received VTP message is correct, its  
information is accepted.  
VTP Pruning  
VTP pruning increases network available bandwidth by restricting flooded traffic to those trunk links  
that the traffic must use to reach the destination devices. Without VTP pruning, a switch floods  
broadcast, multicast, and unknown unicast traffic across all trunk links within a VTP domain even  
though receiving switches might discard them. VTP pruning is disabled by default.  
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Chapter 13 Configuring VTP  
Understanding VTP  
VTP pruning blocks unneeded flooded traffic to VLANs on trunk ports that are included in the  
pruning-eligible list. Only VLANs included in the pruning-eligible list can be pruned. By default,  
VLANs 2 through 1001 are pruning eligible switch trunk ports. If the VLANs are configured as  
pruning-ineligible, the flooding continues. VTP pruning is supported with VTP version 1 and version 2.  
Figure 13-1 shows a switched network without VTP pruning enabled. Port 1 on Switch A and Port 2 on  
Switch D are assigned to the Red VLAN. If a broadcast is sent from the host connected to Switch A,  
Switch A floods the broadcast and every switch in the network receives it, even though Switches C, E,  
and F have no ports in the Red VLAN.  
Figure 13-1  
Flooding Traffic without VTP Pruning  
Switch D  
Port 2  
Switch E  
Switch B  
Red  
VLAN  
Port 1  
Switch F  
Switch C  
Switch A  
Figure 13-2 shows a switched network with VTP pruning enabled. The broadcast traffic from Switch A  
is not forwarded to Switches C, E, and F because traffic for the Red VLAN has been pruned on the links  
shown (Port 5 on Switch B and Port 4 on Switch D).  
Figure 13-2  
Optimized Flooded Traffic with VTP Pruning  
Switch D  
Port 2  
Flooded traffic  
Port  
4
is pruned.  
Switch B  
Red  
VLAN  
Switch E  
Flooded traffic  
Port  
5
is pruned.  
Switch C  
Port 1  
Switch F  
Switch A  
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Chapter 13 Configuring VTP  
Configuring VTP  
Enabling VTP pruning on a VTP server enables pruning for the entire management domain. Making  
VLANs pruning-eligible or pruning-ineligible affects pruning eligibility for those VLANs on that device  
only (not on all switches in the VTP domain). See the “Enabling VTP Pruning” section on page 13-13.  
VTP pruning takes effect several seconds after you enable it. VTP pruning does not prune traffic from  
VLANs that are pruning-ineligible. VLAN 1 and VLANs 1002 to 1005 are always pruning-ineligible;  
traffic from these VLANs cannot be pruned. Extended-range VLANs (VLAN IDs higher than 1005) are  
also pruning-ineligible.  
VTP pruning is not designed to function in VTP transparent mode. If one or more switches in the  
network are in VTP transparent mode, you should do one of these:  
•
•
Turn off VTP pruning in the entire network.  
Turn off VTP pruning by making all VLANs on the trunk of the switch upstream to the VTP  
transparent switch pruning ineligible.  
To configure VTP pruning on an interface, use the switchport trunk pruning vlan interface  
configuration command (see the “Changing the Pruning-Eligible List” section on page 12-20). VTP  
pruning operates when an interface is trunking. You can set VLAN pruning-eligibility, whether or not  
VTP pruning is enabled for the VTP domain, whether or not any given VLAN exists, and whether or not  
the interface is currently trunking.  
Configuring VTP  
This section includes guidelines and procedures for configuring VTP. These sections are included:  
•
•
•
•
•
•
•
•
•
Default VTP Configuration, page 13-6  
VTP Configuration Options, page 13-7  
VTP Configuration Guidelines, page 13-8  
Configuring a VTP Server, page 13-9  
Configuring a VTP Client, page 13-10  
Disabling VTP (VTP Transparent Mode), page 13-11  
Enabling VTP Version 2, page 13-12  
Enabling VTP Pruning, page 13-13  
Adding a VTP Client Switch to a VTP Domain, page 13-14  
Default VTP Configuration  
Table 13-2 shows the default VTP configuration.  
Table 13-2  
Default VTP Configuration  
Feature  
Default Setting  
VTP domain name  
VTP mode  
Null.  
Transparent.  
Version 2 is disabled.  
None.  
VTP version 2 enable state  
VTP password  
VTP pruning  
Disabled.  
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Chapter 13 Configuring VTP  
Configuring VTP  
VTP Configuration Options  
You can configure VTP by using these configuration modes.  
•
•
VTP Configuration in Global Configuration Mode, page 13-7  
VTP Configuration in VLAN Configuration Mode, page 13-7  
You access VLAN configuration mode by entering the vlan database privileged EXEC command.  
For detailed information about vtp commands, see the command reference for this release.  
VTP Configuration in Global Configuration Mode  
You can use the vtp global configuration command to set the VTP password, the version, the VTP file  
name, the interface providing updated VTP information, the domain name, and the mode, and to disable  
or enable pruning. For more information about available keywords, see the command descriptions in the  
command reference for this release. The VTP information is saved in the VTP VLAN database. When  
VTP mode is transparent, the VTP domain name and mode are also saved in the switch running  
configuration file, and you can save it in the switch startup configuration file by entering the copy  
running-config startup-config privileged EXEC command. You must use this command if you want to  
save VTP mode as transparent, even if the switch resets.  
When you save VTP information in the switch startup configuration file and reboot the switch, the  
switch configuration is determined as follows:  
•
If the VTP mode is transparent in the startup configuration and the VLAN database and the VTP  
domain name from the VLAN database matches that in the startup configuration file, the VLAN  
database is ignored (cleared), and the VTP and VLAN configurations in the startup configuration  
file are used. The VLAN database revision number remains unchanged in the VLAN database.  
•
If the VTP mode or domain name in the startup configuration do not match the VLAN database, the  
domain name and VTP mode and configuration for the first 1005 VLAN IDs use the VLAN database  
information.  
VTP Configuration in VLAN Configuration Mode  
You can configure all VTP parameters in VLAN configuration mode, which you access by entering the  
vlan database privileged EXEC command. For more information about available keywords, see the vtp  
VLAN configuration command description in the command reference for this release. When you enter  
the exit command in VLAN configuration mode, it applies all the commands that you entered and  
updates the VLAN database. VTP messages are sent to other switches in the VTP domain, and the  
privileged EXEC mode prompt appears.  
If VTP mode is transparent, the domain name and the mode (transparent) are saved in the switch running  
configuration, and you can save this information in the switch startup configuration file by entering the  
copy running-config startup-config privileged EXEC command.  
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Chapter 13 Configuring VTP  
Configuring VTP  
VTP Configuration Guidelines  
These sections describe guidelines you should follow when implementing VTP in your network.  
Domain Names  
When configuring VTP for the first time, you must always assign a domain name. You must configure  
all switches in the VTP domain with the same domain name. Switches in VTP transparent mode do not  
exchange VTP messages with other switches, and you do not need to configure a VTP domain name  
for them.  
Note  
If NVRAM and DRAM storage is sufficient, all switches in a VTP domain should be in VTP server  
mode.  
Caution  
Do not configure a VTP domain if all switches are operating in VTP client mode. If you configure the  
domain, it is impossible to make changes to the VLAN configuration of that domain. Make sure that you  
configure at least one switch in the VTP domain for VTP server mode.  
Passwords  
You can configure a password for the VTP domain, but it is not required. If you do configure a domain  
password, all domain switches must share the same password and you must configure the password on  
each switch in the management domain. Switches without a password or with the wrong password reject  
VTP advertisements.  
If you configure a VTP password for a domain, a switch that is booted without a VTP configuration does  
not accept VTP advertisements until you configure it with the correct password. After the configuration,  
the switch accepts the next VTP advertisement that uses the same password and domain name in the  
advertisement.  
If you are adding a new switch to an existing network with VTP capability, the new switch learns the  
domain name only after the applicable password has been configured on it.  
Caution  
When you configure a VTP domain password, the management domain does not function properly if you  
do not assign a management domain password to each switch in the domain.  
VTP Version  
Follow these guidelines when deciding which VTP version to implement:  
•
•
All switches in a VTP domain must run the same VTP version.  
A VTP version 2-capable switch can operate in the same VTP domain as a switch running VTP  
version 1 if version 2 is disabled on the version 2-capable switch (version 2 is disabled by default).  
•
Do not enable VTP version 2 on a switch unless all of the switches in the same VTP domain are  
version-2-capable. When you enable version 2 on a switch, all of the version-2-capable switches in  
the domain enable version 2. If there is a version 1-only switch, it does not exchange VTP  
information with switches with version 2 enabled.  
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Chapter 13 Configuring VTP  
Configuring VTP  
•
If there are TrBRF and TrCRF Token Ring networks in your environment, you must enable VTP  
version 2 for Token Ring VLAN switching to function properly. To run Token Ring and Token  
Ring-Net, disable VTP version 2.  
Configuration Requirements  
When you configure VTP, you must configure a trunk port so that the switch can send and receive VTP  
advertisements. For more information, see the “Configuring VLAN Trunks” section on page 12-14.  
If you are configuring extended-range VLANs on the switch, the switch must be in VTP transparent  
mode.  
Configuring a VTP Server  
When a switch is in VTP server mode, you can change the VLAN configuration and have it propagated  
throughout the network.  
Note  
If extended-range VLANs are configured on the switch, you cannot change VTP mode to server. You  
receive an error message, and the configuration is not allowed.  
Beginning in privileged EXEC mode, follow these steps to configure the switch as a VTP server:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
vtp mode server  
Enter global configuration mode.  
Configure the switch for VTP server mode.  
vtp domain domain-name  
Configure the VTP administrative-domain name. The name can be from  
1 to 32 characters. All switches operating in VTP server or client mode  
under the same administrative responsibility must be configured with the  
same domain name.  
Step 4  
vtp password password  
(Optional) Set the password for the VTP domain. The password can be  
from 8 to 64 characters.  
If you configure a VTP password, the VTP domain does not function  
properly if you do not assign the same password to each switch in the  
domain.  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show vtp status  
Verify your entries in the VTP Operating Mode and the VTP Domain Name  
fields of the display.  
When you configure a domain name, it cannot be removed; you can only reassign a switch to a different  
domain.  
To return the switch to a no-password state, use the no vtp password global configuration command.  
This example shows how to use global configuration mode to configure the switch as a VTP server with  
the domain name eng_group and the password mypassword:  
Switch# config terminal  
Switch(config)# vtp mode server  
Switch(config)# vtp domain eng_group  
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Chapter 13 Configuring VTP  
Configuring VTP  
Switch(config)# vtp password mypassword  
Switch(config)# end  
You can also use VLAN configuration mode to configure VTP parameters. Beginning in privileged  
EXEC mode, follow these steps to use VLAN configuration mode to configure the switch as a VTP  
server:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
vlan database  
Enter VLAN configuration mode.  
vtp server  
Configure the switch for VTP server mode (the default).  
vtp domain domain-name  
Configure a VTP administrative-domain name. The name can be from 1 to 32  
characters. All switches operating in VTP server or client mode under the  
same administrative responsibility must be configured with the same domain  
name.  
Step 4  
vtp password password  
(Optional) Set a password for the VTP domain. The password can be from 8  
to 64 characters.  
If you configure a VTP password, the VTP domain does not function properly  
if you do not assign the same password to each switch in the domain.  
Step 5  
Step 6  
exit  
Update the VLAN database, propagate it throughout the administrative  
domain, and return to privileged EXEC mode.  
show vtp status  
Verify your entries in the VTP Operating Mode and the VTP Domain Name  
fields of the display.  
When you configure a domain name, it cannot be removed; you can only reassign a switch to a different  
domain.  
To return the switch to a no-password state, use the no vtp password VLAN configuration command.  
This example shows how to use VLAN configuration mode to configure the switch as a VTP server with  
the domain name eng_group and the password mypassword:  
Switch# vlan database  
Switch(vlan)# vtp server  
Switch(vlan)# vtp domain eng_group  
Switch(vlan)# vtp password mypassword  
Switch(vlan)# exit  
APPLY completed.  
Exiting....  
Configuring a VTP Client  
When a switch is in VTP client mode, you cannot change its VLAN configuration. The client switch  
receives VTP updates from a VTP server in the VTP domain and then modifies its configuration  
accordingly.  
Note  
If extended-range VLANs are configured on the switch, you cannot change VTP mode to client. You  
receive an error message, and the configuration is not allowed.  
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Chapter 13 Configuring VTP  
Configuring VTP  
Caution  
If all switches are operating in VTP client mode, do not configure a VTP domain name. If you do, it is  
impossible to make changes to the VLAN configuration of that domain. Therefore, make sure you  
configure at least one switch as a VTP server.  
Beginning in privileged EXEC mode, follow these steps to configure the switch as a VTP client:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
vtp mode client  
Enter global configuration mode.  
Configure the switch for VTP client mode. The default setting is VTP  
server.  
Step 3  
vtp domain domain-name  
(Optional) Enter the VTP administrative-domain name. The name can be  
from 1 to 32 characters. This should be the same domain name as the VTP  
server.  
All switches operating in VTP server or client mode under the same  
administrative responsibility must be configured with the same domain  
name.  
Step 4  
Step 5  
Step 6  
vtp password password  
end  
(Optional) Enter the password for the VTP domain.  
Return to privileged EXEC mode.  
show vtp status  
Verify your entries in the VTP Operating Mode and the VTP Domain Name  
fields of the display.  
Use the no vtp mode global configuration command to return the switch to VTP server mode. To return  
the switch to a no-password state, use the no vtp password global configuration command. When you  
configure a domain name, it cannot be removed; you can only reassign a switch to a different domain.  
Note  
You can also configure a VTP client by using the vlan database privileged EXEC command to enter  
VLAN configuration mode and entering the vtp client command, similar to the second procedure under  
“Configuring a VTP Server” section on page 13-9. Use the no vtp client VLAN configuration command  
to return the switch to VTP server mode or the no vtp password VLAN configuration command to return  
the switch to a no-password state. When you configure a domain name, it cannot be removed; you can  
only reassign a switch to a different domain.  
Disabling VTP (VTP Transparent Mode)  
When you configure the switch for VTP transparent mode, VTP is disabled on the switch. The switch  
does not send VTP updates and does not act on VTP updates received from other switches. However, a  
VTP transparent switch running VTP version 2 does forward received VTP advertisements on its trunk  
links.  
Note  
Before you create extended-range VLANs (VLAN IDs 1006 to 4094), you must set VTP mode to  
transparent by using the vtp mode transparent global configuration command. Save this configuration  
to the startup configuration so that the switch boots up in VTP transparent mode. Otherwise, you lose  
the extended-range VLAN configuration if the switch resets and boots up in VTP server mode (the  
default).  
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Chapter 13 Configuring VTP  
Configuring VTP  
Beginning in privileged EXEC mode, follow these steps to configure VTP transparent mode and save  
the VTP configuration in the switch startup configuration file:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
configure terminal  
vtp mode transparent  
end  
Enter global configuration mode.  
Configure the switch for VTP transparent mode (disable VTP).  
Return to privileged EXEC mode.  
show vtp status  
Verify your entries in the VTP Operating Mode and the VTP Domain  
Name fields of the display.  
Step 5  
copy running-config startup-config  
(Optional) Save the configuration in the startup configuration file.  
Note  
Only VTP mode and domain name are saved in the switch running  
configuration and can be copied to the startup configuration file.  
To return the switch to VTP server mode, use the no vtp mode global configuration command.  
Note  
Note  
If extended-range VLANs are configured on the switch, you cannot change VTP mode to server. You  
receive an error message, and the configuration is not allowed.  
You can also configure VTP transparent mode by using the vlan database privileged EXEC command  
to enter VLAN configuration mode and by entering the vtp transparent command, similar to the second  
procedure under the “Configuring a VTP Server” section on page 13-9. Use the no vtp transparent  
VLAN configuration command to return the switch to VTP server mode. If extended-range VLANs are  
configured on the switch, you cannot change VTP mode to server. You receive an error message, and  
the configuration is not allowed.  
Enabling VTP Version 2  
VTP version 2 is disabled by default on VTP version 2-capable switches. When you enable VTP  
version 2 on a switch, every VTP version 2-capable switch in the VTP domain enables version 2. You  
can only configure the version on switches in VTP server or transparent mode.  
Caution  
Note  
VTP version 1 and VTP version 2 are not interoperable on switches in the same VTP domain. Every  
switch in the VTP domain must use the same VTP version. Do not enable VTP version 2 unless every  
switch in the VTP domain supports version 2.  
In TrCRF and TrBRF Token ring environments, you must enable VTP version 2 for Token Ring VLAN  
switching to function properly. For Token Ring and Token Ring-Net media, VTP version 2 must be  
disabled.  
For more information on VTP version configuration guidelines, see the “VTP Version” section on  
page 13-8.  
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Chapter 13 Configuring VTP  
Configuring VTP  
Beginning in privileged EXEC mode, follow these steps to enable VTP version 2:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
vtp version 2  
Enter global configuration mode.  
Enable VTP version 2 on the switch.  
VTP version 2 is disabled by default on VTP version 2-capable switches.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
end  
show vtp status  
Verify that VTP version 2 is enabled in the VTP V2 Mode field of the display.  
To disable VTP version 2, use the no vtp version global configuration command.  
Note  
You can also enable VTP version 2 by using the vlan database privileged EXEC command to enter  
VLAN configuration mode and entering the vtp v2-mode VLAN configuration command. To disable  
VTP version 2, use the no vtp v2-mode VLAN configuration command.  
Enabling VTP Pruning  
Pruning increases available bandwidth by restricting flooded traffic to those trunk links that the traffic  
must use to access the destination devices. You can only enable VTP pruning on a switch in VTP server  
mode.  
Beginning in privileged EXEC mode, follow these steps to enable VTP pruning in the VTP domain:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
vtp pruning  
Enter global configuration mode.  
Enable pruning in the VTP administrative domain.  
By default, pruning is disabled. You need to enable pruning on only one switch  
in VTP server mode.  
Step 3  
Step 4  
end  
Return to privileged EXEC mode.  
show vtp status  
Verify your entries in the VTP Pruning Mode field of the display.  
To disable VTP pruning, use the no vtp pruning global configuration command.  
Note  
You can also enable VTP pruning by using the vlan database privileged EXEC command to enter  
VLAN configuration mode and entering the vtp pruning VLAN configuration command. To disable  
VTP pruning, use the no vtp pruning VLAN configuration command.  
Pruning is supported with VTP version 1 and version 2. If you enable pruning on the VTP server, it is  
enabled for the entire VTP domain.  
Only VLANs included in the pruning-eligible list can be pruned. By default, VLANs 2 through 1001 are  
pruning eligible on trunk ports. Extended-range VLANs cannot be pruned. To change the  
pruning-eligible VLANs, see the “Changing the Pruning-Eligible List” section on page 12-20.  
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Chapter 13 Configuring VTP  
Configuring VTP  
Adding a VTP Client Switch to a VTP Domain  
Before adding a VTP client to a VTP domain, always verify that its VTP configuration revision number  
is lower than the configuration revision number of the other switches in the VTP domain. Switches in a  
VTP domain always use the VLAN configuration of the switch with the highest VTP configuration  
revision number. If you add a switch that has a revision number higher than the revision number in the  
VTP domain, it can erase all VLAN information from the VTP server and VTP domain.  
Beginning in privileged EXEC mode, follow these steps to verify and reset the VTP configuration  
revision number on a switch before adding it to a VTP domain:  
Command  
Purpose  
Step 1  
show vtp status  
Check the VTP configuration revision number.  
If the number is 0, add the switch to the VTP domain.  
If the number is greater than 0, follow these steps:  
a. Write down the domain name.  
b. Write down the configuration revision number.  
c. Continue with the next steps to reset the configuration revision number on the  
switch.  
Step 2  
Step 3  
Step 4  
configure terminal  
vtp domain domain-name  
end  
Enter global configuration mode.  
Change the domain name from the original one displayed in Step 1 to a new name.  
The VLAN information on the switch is updated and the configuration revision  
number is reset to 0. You return to privileged EXEC mode.  
Step 5  
Step 6  
Step 7  
Step 8  
show vtp status  
configure terminal  
vtp domain domain-name  
end  
Verify that the configuration revision number has been reset to 0.  
Enter global configuration mode.  
Enter the original domain name on the switch.  
The VLAN information on the switch is updated, and you return to privileged EXEC  
mode.  
Step 9  
show vtp status  
(Optional) Verify that the domain name is the same as in Step 1 and that the  
configuration revision number is 0.  
You can also change the VTP domain name by entering the vlan database privileged EXEC command  
to enter VLAN configuration mode and by entering the vtp domain domain-name command. In this  
mode, you must enter the exit command to update VLAN information and return to privileged EXEC  
mode.  
After resetting the configuration revision number, add the switch to the VTP domain.  
Note  
You can use the vtp mode transparent global configuration command or the vtp transparent VLAN  
configuration command to disable VTP on the switch, and then change its VLAN information without  
affecting the other switches in the VTP domain.  
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Chapter 13 Configuring VTP  
Monitoring VTP  
Monitoring VTP  
You monitor VTP by displaying VTP configuration information: the domain name, the current VTP  
revision, and the number of VLANs. You can also display statistics about the advertisements sent and  
received by the switch.  
Table 13-3 shows the privileged EXEC commands for monitoring VTP activity.  
Table 13-3  
VTP Monitoring Commands  
Command  
Purpose  
show vtp status  
Display the VTP switch configuration information.  
show vtp counters  
Display counters about VTP messages that have been sent and received.  
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Chapter 13 Configuring VTP  
Monitoring VTP  
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C H A P T E R  
14  
Configuring IGMP Snooping and MVR  
This chapter describes how to configure Internet Group Management Protocol (IGMP) snooping on your  
Cisco Systems Intelligent Gigabit Ethernet Switch Module, including an application of local IGMP  
snooping, Multicast VLAN Registration (MVR). It also includes procedures for controlling multicast  
group membership by using IGMP filtering and procedures for configuring the IGMP throttling action.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the switch  
command reference for this release and the Cisco IOS Release Network Protocols Command Reference,  
Part 1, for Cisco IOS Release 12.1  
This chapter consists of these sections:  
•
•
•
•
•
•
•
•
Understanding IGMP Snooping, page 14-2  
Configuring IGMP Snooping, page 14-7  
Displaying IGMP Snooping Information, page 14-14  
Understanding Multicast VLAN Registration, page 14-15  
Configuring MVR, page 14-17  
Displaying MVR Information, page 14-21  
Configuring IGMP Filtering and Throttling, page 14-21  
Displaying IGMP Filtering and Throttling Configuration, page 14-27  
Note  
For MAC addresses that map to IP multicast groups, you can either manage them through features such  
as IGMP snooping and MVR, or you can use static MAC addresses. However, you cannot use both  
methods simultaneously. Therefore, before using IGMP snooping or MVR, you should remove all  
statically configured MAC addresses that map to IP multicast groups.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Understanding IGMP Snooping  
Understanding IGMP Snooping  
Layer 2 switches can use IGMP snooping to constrain the flooding of multicast traffic by dynamically  
configuring Layer 2 interfaces so that multicast traffic is forwarded to only those interfaces associated  
with IP multicast devices. As the name implies, IGMP snooping requires the LAN switch to snoop on  
the IGMP transmissions between the host and the router and to keep track of multicast groups and  
member ports. When the switch receives an IGMP report from a host for a particular multicast group,  
the switch adds the host port number to the forwarding table entry; when it receives an IGMP Leave  
Group message from a host, it removes the host port from the table entry. It also periodically deletes  
entries if it does not receive IGMP membership reports from the multicast clients.  
Note  
For more information on IP multicast and IGMP, see RFC 1112 and RFC 2236.  
The multicast router sends out periodic IGMP general queries to all VLANs. When IGMP snooping is  
enabled, the switch responds to the router queries with only one join request per MAC multicast group,  
and the switch creates one entry per VLAN in the Layer 2 forwarding table for each MAC group from  
which it receives an IGMP join request. All hosts interested in this multicast traffic send join requests  
and are added to the forwarding table entry.  
Layer 2 multicast groups learned through IGMP snooping are dynamic. However, you can statically  
configure MAC multicast groups by using the ip igmp snooping vlan static global configuration  
command. If you specify group membership for a multicast group address statically, your setting  
supersedes any automatic manipulation by IGMP snooping. Multicast group membership lists can  
consist of both user-defined and IGMP snooping-learned settings.  
If a port spanning-tree, a port group, or a VLAN ID change occurs, the IGMP snooping-learned multicast  
groups from this port on the VLAN are deleted.  
The switches support a maximum of 255 IP multicast groups and support both IGMP version 1 and  
IGMP version 2.  
These sections describe characteristics of IGMP snooping on the switch:  
•
•
•
•
•
•
•
IGMP Versions, page 14-2  
Joining a Multicast Group, page 14-3  
Leaving a Multicast Group, page 14-5  
Immediate-Leave Processing, page 14-6  
IGMP Configurable-Leave Timer, page 14-6  
IGMP Report Suppression, page 14-6  
Source-Only Networks, page 14-7  
IGMP Versions  
The switch supports IGMP version 1, IGMP version 2, and IGMP version 3. These versions are  
interoperable on the switch. For example, if IGMP snooping is enabled on an IGMPv2 switch and the  
switch receives an IGMPv3 report from a host, the switch can forward the IGMPv3 report to the  
multicast router.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Understanding IGMP Snooping  
Note  
The switch supports IGMPv3 snooping based only on the destination multicast MAC address. It does  
not support snooping based on the source MAC address or on proxy reports.  
An IGMPv3 switch supports Basic IGMPv3 Snooping Support (BISS), which includes support for the  
snooping features on IGMPv1 and IGMPv2 switches and for IGMPv3 membership report messages.  
BISS constrains the flooding of multicast traffic when your network includes IGMPv3 hosts. It  
constrains traffic to approximately the same set of ports as the IGMP snooping feature on IGMPv2 or  
IGMPv1 hosts.  
Note  
IGMPv3 join and leave messages are not supported on switches running IGMP filtering or MVR.  
An IGMPv3 switch can receive messages from and forward messages to a device running the Source  
Specific Multicast (SSM) feature. For more information, see the “Configuring IP Multicast Layer 3  
Switching” chapter in the Catalyst 4500 Series Switch Cisco IOS Software Configuration Guide, Cisco  
IOS Release 12.1(12c)EW at this URL:  
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat4000/12_1_12/config/mcastmls.htm  
Joining a Multicast Group  
When a host connected to the switch wants to join an IP multicast group, it sends an unsolicited IGMP  
join message, specifying the IP multicast group to join. Alternatively, when the switch receives a general  
query from the router, it forwards the query to all ports in the VLAN. Hosts wanting to join the multicast  
group respond by sending a join message to the switch. The switch CPU creates a multicast  
forwarding-table entry for the group if it is not already present. The CPU also adds the interface where  
the join message was received to the forwarding-table entry. The host associated with that interface  
receives multicast traffic for that multicast group. See Figure 14-1.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Understanding IGMP Snooping  
Figure 14-1  
Initial IGMP Join Message  
Router A  
1
IGMP report 224.1.2.3  
IGESM  
Switching engine  
CPU  
0
Forwarding  
table  
2
3
4
5
Server  
Blade 1  
Server  
Blade 2  
Server  
Blade 3  
Server  
Blade 4  
Router A sends a general query to the switch, which forwards the query to ports 2 through 5, all members  
of the same VLAN. Host 1 wants to join multicast group 224.1.2.3 and multicasts an IGMP membership  
report (IGMP join message) to the group with the equivalent MAC destination address of  
0x0100.5E01.0203. When the CPU receives the IGMP report multicast by Host 1, the CPU uses the  
information in the IGMP report to set up a forwarding-table entry, as shown in Table 14-1, that includes  
the port numbers of Host 1, the router, and the switch internal CPU.  
Table 14-1  
IGMP Snooping Forwarding Table  
Destination Address  
0100.5exx.xxxx  
0100.5e01.0203  
Type of Packet  
IGMP  
Ports  
0
!IGMP  
1, 2  
Note that the switch hardware can distinguish IGMP information packets from other packets for the  
multicast group.  
•
The first entry in the table tells the switching engine to send IGMP packets to only the switch CPU.  
This prevents the CPU from becoming overloaded with multicast frames.  
•
The second entry tells the switching engine to send frames addressed to the 0x0100.5E01.0203  
multicast MAC address that are not IGMP packets (!IGMP) to the router and to the host that has  
joined the group.  
If another host (for example, Host 4) sends an unsolicited IGMP join message for the same group  
(Figure 14-2), the CPU receives that message and adds the port number of Host 4 to the forwarding table  
as shown in Table 14-2. Note that because the forwarding table directs IGMP messages only to the CPU,  
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Chapter 14 Configuring IGMP Snooping and MVR  
Understanding IGMP Snooping  
the message is not flooded to other ports on the switch. Any known multicast traffic is forwarded to the  
group and not to the CPU. Any unknown multicast traffic is flooded to the VLAN and sent to the CPU  
until it becomes known.  
Figure 14-2  
Second Host Joining a Multicast Group  
Router A  
1
IGESM  
Switching engine  
0
CPU  
Forwarding  
table  
2
3
4
5
Server  
Blade 1  
Server  
Blade 2  
Server  
Blade 3  
Server  
Blade 4  
Table 14-2  
Updated IGMP Snooping Forwarding Table  
Destination Address  
0100.5exx.xxxx  
0100.5e01.0203  
Type of Packet  
IGMP  
Ports  
0
!IGMP  
1, 2, 5  
Leaving a Multicast Group  
The router sends periodic multicast general queries and the switch forwards these queries through all  
ports in the VLAN. Interested hosts respond to the queries. If at least one host in the VLAN wishes to  
receive multicast traffic, the router continues forwarding the multicast traffic to the VLAN. The switch  
forwards multicast group traffic to only those hosts listed in the forwarding table for that Layer 2  
multicast group.  
When hosts want to leave a multicast group, they can either silently leave, or they can send a leave  
message. When the switch receives a leave message from a host, it sends a group-specific query to  
determine if any other devices connected to that interface are interested in traffic for the specific  
multicast group. The switch then updates the forwarding table for that MAC group so that only those  
hosts interested in receiving multicast traffic for the group are listed in the forwarding table. If the router  
receives no reports from a VLAN, it removes the group for the VLAN from its IGMP cache.  
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Understanding IGMP Snooping  
Immediate-Leave Processing  
Immediate Leave is only supported with IGMP version 2 hosts.  
The switch uses IGMP snooping Immediate-Leave processing to remove from the forwarding table an  
interface that sends a leave message without the switch sending group-specific queries to the interface.  
The VLAN interface is pruned from the multicast tree for the multicast group specified in the original  
leave message. Immediate-Leave processing ensures optimal bandwidth management for all hosts on a  
switched network, even when multiple multicast groups are simultaneously in use.  
Note  
You should only use the Immediate-Leave processing feature on VLANs where a single host is  
connected to each port. If Immediate Leave is enabled in VLANs where more than one host is connected  
to a port, some hosts might inadvertently be dropped.  
IGMP Configurable-Leave Timer  
In Cisco IOS Release 12.1(22)EA2 and earlier, the IGMP snooping leave time was fixed at 5 seconds.  
If membership reports were not received by the switch before the query response time of the query  
expired, a port was removed from the multicast group membership. However, some applications require  
a leave latency of less than 5 seconds.  
In Cisco IOS Release 12.1(22)EA3 and later, you can configure the time that the switch waits after  
sending a group-specific query to determine if hosts are still interested in a specific multicast group. The  
IGMP leave response time can be configured from 100 to 5000 milliseconds. The timer can be set either  
globally or on a per-VLAN basis. The VLAN configuration of the leave time overrides the global  
configuration.  
IGMP Report Suppression  
Note  
IGMP report suppression is supported only when the multicast query has IGMPv1 and IGMPv2 reports.  
This feature is not supported when the query includes IGMPv3 reports.  
The switch uses IGMP report suppression to forward only one IGMP report per multicast router query  
to multicast devices. When IGMP router suppression is enabled (the default), the switch sends the first  
IGMP report from all hosts for a group to all the multicast routers. The switch does not send the  
remaining IGMP reports for the group to the multicast routers. This feature prevents duplicate reports  
from being sent to the multicast devices.  
If the multicast router query includes requests only for IGMPv1 and IGMPv2 reports, the switch  
forwards only the first IGMPv1 or IGMPv2 report from all hosts for a group to all the multicast routers.  
If the multicast router query also includes requests for IGMPv3 reports, the switch forwards all IGMPv1,  
IGMPv2, and IGMPv3 reports for a group to the multicast devices.  
If you disable IGMP report suppression, all IGMP reports are forwarded to the multicast routers.  
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Configuring IGMP Snooping  
Source-Only Networks  
In a source-only network, switch ports are connected to multicast source ports and multicast router ports.  
The switch ports are not connected to hosts that send IGMP join or leave messages.  
The switch learns about IP multicast groups from the IP multicast data stream by using the source-only  
learning method. The switch forwards traffic only to the multicast router ports.  
The default learning method is IP multicast-source-only learning. You can disable IP  
multicast-source-only learning by using the no ip igmp snooping source-only-learning global  
configuration command.  
In addition to IGMP query packets, the switch also uses Protocol-Independent Multicast protocol version  
2 (PIMv2) packets for multicast router discovery. The packets are sent to the switch CPU, which can  
result in a occasional high CPU traffic. You can disable multicast router discovery by PIMv2 packets by  
using the no ip igmp snooping mrouter learn pim v2 global configuration command. This command  
only works when you also disable source-only learning on the switch by using the no ip igmp snooping  
source-only-learning global configuration command.  
By default, the switch ages out forwarding-table entries that were learned by the source-only learning  
method and that are not in use. If the aging time is too long or is disabled, the forwarding table is filled  
with unused entries that the switch learned by using source-only learning or by using the IGMP join  
messages. When the switch receives traffic for new IP multicast groups, it floods the packet to all ports  
in the same VLAN. This unnecessary flooding can impact switch performance.  
If aging is disabled and you want to delete multicast addresses that the switch learned by using  
source-only learning, re-enable aging of the forwarding-table entries. The switch can now age out the  
multicast addresses that were learned by the source-only learning method and are not in use.  
Configuring IGMP Snooping  
IGMP snooping allows switches to examine IGMP packets and make forwarding decisions based on  
their content.  
These sections describe how to configure IGMP snooping:  
•
•
•
•
•
•
•
•
•
•
Default IGMP Snooping Configuration, page 14-8  
Enabling or Disabling IGMP Snooping, page 14-8  
Setting the Snooping Method, page 14-9  
Configuring a Multicast Router Port, page 14-10  
Configuring a Host Statically to Join a Group, page 14-10  
Enabling IGMP Immediate-Leave Processing, page 14-11  
Configuring the IGMP Leave Timer, page 14-12  
Disabling IGMP Report Suppression, page 14-12  
Disabling IP Multicast-Source-Only Learning, page 14-13  
Configuring the Aging Time, page 14-14  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring IGMP Snooping  
Default IGMP Snooping Configuration  
Table 14-3 shows the default IGMP snooping configuration.  
Table 14-3  
Default IGMP Snooping Configuration  
Feature  
Default Setting  
IGMP snooping  
Enabled globally and per VLAN.  
None configured.  
PIM-DVMRP.  
Disabled.  
Multicast routers  
Multicast router learning (snooping) method  
IGMP snooping Immediate Leave  
Static groups  
None configured.  
Enabled.  
IP multicast-source-only learning  
PIM v2 multicast router discovery  
Enabled  
Aging forward-table entries (when source-only  
learning is enabled)  
Enabled. The default is 600 seconds  
(10 minutes).  
IGMP report suppression  
Enabled.  
Enabling or Disabling IGMP Snooping  
By default, IGMP snooping is globally enabled on the switch. When globally enabled or disabled, it is  
also enabled or disabled in all existing VLAN interfaces. IGMP snooping is by default enabled on all  
VLANs, but can be enabled and disabled on a per-VLAN basis.  
Global IGMP snooping overrides the VLAN IGMP snooping. If global snooping is disabled, you cannot  
enable VLAN snooping. If global snooping is enabled, you can enable or disable VLAN snooping.  
Beginning in privileged EXEC mode, follow these steps to globally enable IGMP snooping on the  
switch:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
configure terminal  
ip igmp snooping  
end  
Enter global configuration mode.  
Globally enable IGMP snooping in all existing VLAN interfaces.  
Return to privileged EXEC mode.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To globally disable IGMP snooping on all VLAN interfaces, use the no ip igmp snooping global  
configuration command.  
Beginning in privileged EXEC mode, follow these steps to enable IGMP snooping on a VLAN interface:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ip igmp snooping vlan vlan-id  
Enable IGMP snooping on the VLAN interface.  
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Configuring IGMP Snooping  
Command  
Purpose  
Step 3  
Step 4  
end  
Return to privileged EXEC mode.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable IGMP snooping on a VLAN interface, use the no ip igmp snooping vlan vlan-id global  
configuration command for the specified VLAN number.  
Setting the Snooping Method  
Multicast-capable router ports are added to the forwarding table for every Layer 2 multicast entry. The  
switch learns of such ports through one of these methods:  
•
Snooping on IGMP queries, Protocol Independent Multicast (PIM) packets, and Distance Vector  
Multicast Routing Protocol (DVMRP) packets  
•
•
Listening to Cisco Group Management Protocol (CGMP) packets from other routers  
Statically connecting to a multicast router port with the ip igmp snooping mrouter global  
configuration command  
You can configure the switch either to snoop on IGMP queries and PIM/DVMRP packets or to listen to  
CGMP self-join or proxy-join packets. By default, the switch snoops on PIM/DVMRP packets on all  
VLANs. To learn of multicast router ports through only CGMP packets, use the ip igmp snooping vlan  
vlan-id mrouter learn cgmp global configuration command. When this command is entered, the router  
listens to only CGMP self-join and CGMP proxy-join packets and no other CGMP packets. To learn of  
multicast router ports through only PIM-DVMRP packets, use the ip igmp snooping vlan vlan-id  
mrouter learn pim-dvmrp global configuration command.  
Beginning in privileged EXEC mode, follow these steps to alter the method in which a VLAN interface  
dynamically accesses a multicast router:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ip igmp snooping vlan vlan-id mrouter  
learn {cgmp | pim-dvmrp}  
Enable IGMP snooping on a VLAN. The VLAN ID range is 1 to 4094.  
Specify the multicast router learning method:  
•
cgmp—Listen for CGMP packets. This method is useful for  
reducing control traffic.  
•
pim-dvmrp—Snoop on IGMP queries and PIM-DVMRP packets.  
This is the default.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify the configuration.  
show ip igmp snooping  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Configuring IGMP Snooping  
This example shows how to configure IGMP snooping to use CGMP packets as the learning method:  
Switch# configure terminal  
Switch(config)# ip igmp snooping vlan 1 mrouter learn cgmp  
Switch(config)# end  
To return to the default learning method, use the no ip igmp snooping vlan vlan-id mrouter learn cgmp  
global configuration command.  
Configuring a Multicast Router Port  
To add a multicast router port (add a static connection to a multicast router), use the ip igmp snooping  
vlan mrouter global configuration command on the switch.  
Beginning in privileged EXEC mode, follow these steps to enable a static connection to a multicast  
router:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ip igmp snooping vlan vlan-id mrouter  
interface interface-id  
Specify the multicast router VLAN ID and specify the interface  
to the multicast router. The VLAN ID range is 1 to 4094.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
show ip igmp snooping mrouter [vlan vlan-id] Verify that IGMP snooping is enabled on the VLAN interface.  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To remove a multicast router port from the VLAN, use the no ip igmp snooping vlan vlan-id mrouter  
interface interface-id global configuration command.  
This example shows how to enable a static connection to a multicast router and verify the configuration:  
Switch# configure terminal  
Switch(config)# ip igmp snooping vlan 200 mrouter interface gigabitethernet0/17  
Switch(config)# end  
Configuring a Host Statically to Join a Group  
Hosts or Layer 2 ports normally join multicast groups dynamically, but you can also statically configure  
a host on an interface.  
Beginning in privileged EXEC mode, follow these steps to add a Layer 2 port as a member of a multicast  
group:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode  
ip igmp snooping vlan vlan-id static  
mac-address interface interface-id  
Statically configure a Layer 2 port as a member of a multicast  
group:  
•
•
•
vlan-id is the multicast group VLAN ID.  
mac-address is the group MAC address.  
interface-id is the member port.  
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Configuring IGMP Snooping  
Command  
Purpose  
Step 3  
end  
Return to privileged EXEC mode.  
Step 4  
show ip igmp snooping mrouter vlan vlan-id  
Verify that the member port is a member of the VLAN multicast  
group.  
or  
show mac address-table multicast vlan vlan-id Verify the member port and the MAC address  
Step 5  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To remove the Layer 2 port from the multicast group, use the no ip igmp snooping vlan vlan-id static  
mac-address interface interface-id global configuration command.  
This example shows how to statically configure a host on an interface and verify the configuration:  
Switch# configure terminal  
Switch(config)# ip igmp snooping vlan 1 static 0100.5e00.0203 interface  
gigabitethernet0/17  
Switch(config)# end  
Enabling IGMP Immediate-Leave Processing  
When you enable IGMP Immediate-Leave processing, the switch immediately removes a port when it  
detects an IGMP version 2 leave message on that port. You should use the Immediate-Leave feature only  
when there is a single receiver present on every port in the VLAN.  
Note  
Immediate Leave is supported with only IGMP version 2 hosts.  
Beginning in privileged EXEC mode, follow these steps to enable IGMP Immediate-Leave processing:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode  
ip igmp snooping vlan vlan-id  
Enable IGMP Immediate-Leave processing on the VLAN interface.  
immediate-leave  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
show ip igmp snooping vlan vlan-id  
copy running-config startup-config  
Verify that Immediate Leave is enabled on the VLAN.  
(Optional) Save your entries in the configuration file.  
To disable IGMP Immediate-Leave on a VLAN, use the no ip igmp snooping vlan vlan-id  
immediate-leave global configuration command.  
This example shows how to enable IGMP immediate-leave processing on VLAN 130:  
Switch# configure terminal  
Switch(config)# ip igmp snooping vlan 130 immediate-leave  
Switch(config)# end  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring IGMP Snooping  
Configuring the IGMP Leave Timer  
Follows these guidelines when configuring the IGMP leave timer:  
•
•
•
•
•
You can configure the leave time globally or on a per-VLAN basis.  
Configuring the leave time on a VLAN overrides the global setting.  
The default leave time is 1000 milliseconds.  
The IGMP configurable leave time is only supported on hosts running IGMP Version 2.  
The actual leave latency in the network is usually the configured leave time. However, the leave time  
might vary around the configured time, depending on real-time CPU load conditions, network delays  
and the amount of traffic sent through the interface.  
Beginning in privileged EXEC mode, follow these steps to enable the IGMP configurable-leave timer:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ip igmp snooping  
last-member-query-interval time  
Configure the IGMP leave timer globally. The range is 100 to 5000  
milliseconds.  
Step 3  
ip igmp snooping vlan vlan-id  
last-member-query-interval time  
(Optional) Configure the IGMP leave time on the VLAN interface. The  
range is 100 to 5000 milliseconds.  
Note  
Configuring the leave time on a VLAN overrides the globally  
configured timer.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show ip igmp snooping  
copy running-config startup-config  
(Optional) Display the configured IGMP leave time.  
(Optional) Save your entries in the configuration file.  
Use the no ip igmp snooping last-member-query-interval global configuration command to globally  
reset the IGMP leave timer to the default setting (1000 milliseconds).  
Use the no ip igmp snooping vlan vlan-id last-member-query-interval global configuration command  
to remove the configured IGMP leave-time setting from the specified VLAN.  
Disabling IGMP Report Suppression  
IGMP report suppression is enabled by default. When it is enabled, the switch forwards only one IGMP  
report per multicast router query. When report suppression is disabled, all IGMP reports are forwarded  
to the multicast routers.  
Note  
IGMP report suppression is supported only when the multicast query has IGMPv1 and IGMPv2 reports.  
This feature is not supported when the query includes IGMPv3 reports.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring IGMP Snooping  
Beginning in privileged EXEC mode, follow these steps to disable IGMP report suppression:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
Step 5  
configure terminal  
Enter global configuration mode.  
Disable IGMP report suppression.  
Return to privileged EXEC mode.  
no ip igmp snooping report-suppression  
end  
show ip igmp snooping  
copy running-config startup-config  
Verify that IGMP report suppression is disabled.  
(Optional) Save your entries in the configuration file.  
To re-enable IGMP report suppression, use the ip igmp snooping report-suppression global  
configuration command.  
Disabling IP Multicast-Source-Only Learning  
The IP multicast-source-only learning method is enabled by default. The switch learns the IP multicast  
group from the IP multicast data stream and only forwards traffic to the multicast router ports.  
If IP multicast-source-only learning is disabled by using the no ip igmp snooping source-only-learning  
global configuration command, the switch floods unknown multicast traffic to the VLAN and sends the  
traffic to the CPU until the traffic becomes known. When the switch receives an IGMP report from a  
host for a particular multicast group, the switch forwards traffic from this multicast group only to the  
multicast router ports.  
To disable multicast router discovery by PIMv2 packets, you should also enter the no ip igmp snooping  
mrouter learn pim v2 global configuration command.  
Note  
We strongly recommend that you do not disable IP multicast-source-only learning. IP  
multicast-source-only learning should be disabled only if your network is not composed of IP  
multicast-source-only networks and if disabling this learning method improves the network  
performance.  
Beginning in privileged EXEC mode, follow these steps to disable IP multicast-source-only learning:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
Enter global configuration mode  
no ip igmp snooping source-only-learning  
no ip igmp snooping mrouter learn pim v2  
Disable IP multicast-source-only learning.  
(Optional) Disable multicast router discovery by PIM v2  
packets.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
show running-config | include  
source-only-learning  
Verify that IP multicast-source-only learning is disabled.  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Displaying IGMP Snooping Information  
To enable IP multicast-source-only learning, use the ip igmp snooping source-only-learning global  
configuration command. To enable PIM v2 multicast router discovery, use the p igmp snooping  
mrouter learn pim v2 global configuration command.  
This example shows how to disable IP multicast-source-only learning and PIM v2 multicast router  
discovery:  
Switch# configure terminal  
Switch(config)# no ip igmp snooping source-only-learning  
Switch(config)# no ip igmp snooping mrouter learn pim v2  
Switch(config)# end  
Configuring the Aging Time  
You can set the aging time for forwarding-table entries that the switch learns by using the IP  
multicast-source-only learning method.  
Beginning in privileged EXEC mode, follow these steps to configure the aging time:  
Command  
configure terminal  
ip igmp snooping source-only learning age-timer Set the aging time. The range is 0 to 2880 seconds. The default  
Purpose  
Step 1  
Step 2  
Enter global configuration mode  
time  
is 600 seconds (10 minutes).  
Return to privileged EXEC mode.  
Verify the aging time.  
Step 3  
Step 4  
end  
show running-config | include  
source-only-learning  
Step 5  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable the aging of the forwarding table entries, enter the ip igmp snooping source-only-learning  
age-timer 0 global configuration command.  
If you disable source-only learning by using the no ip igmp snooping source-only learning global  
configuration command and the aging time is enabled, it has no effect on the switch.  
Displaying IGMP Snooping Information  
You can display IGMP snooping information for dynamically learned and statically configured router  
ports and VLAN interfaces. You can also display MAC address multicast entries for a VLAN configured  
for IGMP snooping.  
To display IGMP snooping information, use one or more of the privileged EXEC commands in  
Table 14-4.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Understanding Multicast VLAN Registration  
Table 14-4  
Commands for Displaying IGMP Snooping Information  
Purpose  
Command  
show ip igmp snooping [vlan vlan-id]  
Display the snooping configuration information for all VLANs on the  
switch or for a specified VLAN.  
(Optional) Enter vlan vlan-id to display information for a single VLAN.  
show ip igmp snooping group [vlan vlan-id]  
show ip igmp snooping mrouter [vlan vlan-id]  
Display information about the IGMP multicast groups, the compatibility  
mode, and the ports that are associated with each group.  
(Optional) Enter vlan vlan-id to display information for a single VLAN.  
Display information on dynamically learned and manually configured  
multicast router interfaces.  
Note  
When you enable IGMP snooping, the switch automatically  
learns the interface to which a multicast router is connected.  
These are dynamically learned interfaces.  
(Optional) Enter vlan vlan-id to display information for a single VLAN.  
show mac address-table multicast [vlan vlan-id] Display the Layer 2 MAC address table entries for a VLAN. The  
[user | igmp-snooping] [count] keywords are all optional and limit the display as shown:  
•
•
•
vlan vlan-id—Displays only the specified multicast group VLAN.  
user—Displays only the user-configured multicast entries.  
igmp-snooping—Displays only entries learned through IGMP  
snooping.  
•
count—Displays only the total number of entries for the selected  
criteria, not the actual entries.  
For more information about the keywords and options in these commands, see the command reference  
for this release.  
For examples of output from the commands in Table 14-4, see the command reference for this release.  
Understanding Multicast VLAN Registration  
Multicast VLAN Registration (MVR) is designed for applications using wide-scale deployment of  
multicast traffic across an Ethernet ring-based service provider network (for example, the broadcast of  
multiple television channels over a service-provider network). MVR allows a subscriber on a port to  
subscribe and unsubscribe to a multicast stream on the network-wide multicast VLAN. It allows the  
single multicast VLAN to be shared in the network while subscribers remain in separate VLANs. MVR  
provides the ability to continuously send multicast streams in the multicast VLAN, but to isolate the  
streams from the subscriber VLANs for bandwidth and security reasons.  
MVR assumes that subscriber ports subscribe and unsubscribe (join and leave) these multicast streams  
by sending out IGMP join and leave messages. These messages can originate from an IGMP  
version-2-compatible host with an Ethernet connection. Although MVR operates on the underlying  
mechanism of IGMP snooping, the two features operate independently of each other. One can be enabled  
or disabled without affecting the behavior of the other feature. However, if IGMP snooping and MVR  
are both enabled, MVR reacts only to join and leave messages from multicast groups configured under  
MVR. Join and leave messages from all other multicast groups are managed by IGMP snooping.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Understanding Multicast VLAN Registration  
The switch CPU identifies the MVR IP multicast streams and their associated MAC addresses in the  
switch forwarding table, intercepts the IGMP messages, and modifies the forwarding table to include or  
remove the subscriber as a receiver of the multicast stream, even though the receivers might be in a  
different VLAN from the source. This forwarding behavior selectively allows traffic to cross between  
different VLANs.  
The switch has these modes of MVR operation: dynamic and compatible.  
•
When operating in MVR dynamic mode, the switch performs standard IGMP snooping. IGMP  
information packets are sent to the switch CPU, but multicast data packets are not sent to the CPU.  
Dynamic mode allows the multicast router to run normally because the switch sends the IGMP join  
messages to the router, and the router forwards multicast streams for a particular group to an  
interface only if it has received a join message from the interface for the group. Receiver ports are  
treated as members of the multicast VLAN for MVR multicast control and data traffic. IGMP reports  
for MVR groups are sent out source ports in the multicast VLAN.  
•
When in MVR compatible mode, MVR works the same as dynamic mode for all multicast data  
packets and IGMP query and leave packets. However, received IGMP report packets for MVR  
groups are not sent out on the multicast VLAN source ports. In contrast to dynamic mode, the switch  
does not send join messages to the router. The router must be statically configured for the interface  
to receive the multicast stream. Therefore, in this mode, MVR does not support dynamic  
membership joins on source ports.  
Note  
IGMPv3 join and leave messages are not supported on switches running MVR.  
Using MVR in a Multicast Television Application  
In a multicast television application, a PC or a television with a set-top box can receive the multicast  
stream. Multiple set-top boxes or PCs can be connected to one subscriber port, which is a switch port  
configured as an MVR receiver port. Figure 14-3 is an example configuration. When a subscriber selects  
a channel, the set-top box or PC sends an IGMP report to Switch A to join the appropriate multicast. If  
the IGMP report matches one of the configured multicast MAC addresses, the switch CPU modifies the  
hardware address table to include this receiver port and VLAN as a forwarding destination of the  
specified multicast stream when it is received from the multicast VLAN. Uplink ports that send and  
receive multicast data to and from the multicast VLAN are called MVR source ports.  
When a subscriber changes channels or turns off the television, the set-top box sends an IGMP leave  
message for the multicast stream. The switch CPU sends an IGMP group-specific query through the  
receiver port VLAN. If there is another set-top box in the VLAN still subscribing to this group, that  
set-top box must respond within the maximum response time. If the CPU does not receive a response, it  
eliminates the receiver port as a forwarding destination for this group.  
Without Immediate Leave, when the switch receives an IGMP leave message from a subscriber on a  
receiver port, it sends out an IGMP query on that port and waits for IGMP group membership reports. If  
no reports are received in a configured time period, the receiver port is removed from multicast group  
membership. With Immediate Leave, an IGMP query is not sent from the receiver port on which the  
IGMP leave was received. As soon as the leave message is received, the receiver port is removed from  
multicast group membership, which speeds up leave latency. Enable the Immediate Leave feature only  
on receiver ports to which a single receiver device is connected.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring MVR  
Figure 14-3  
Multicast VLAN Registration Example  
Multicast VLAN  
Cisco router  
Multicast  
server  
SP  
Catalyst 3550 switch  
SP  
SP  
Catalyst 2950  
or 2955  
Catalyst 2950  
or 2955  
switch  
switch  
SP  
SP  
SP  
SP1  
SP2  
Multicast  
data  
Multicast  
data  
BladeCenter  
RP = Receiver Port  
SP = Source Port  
Note: All source ports belong to  
the multicast VLAN.  
MVR eliminates the need to duplicate television-channel multicast traffic for subscribers in each VLAN.  
Multicast traffic for all channels is only sent around the VLAN trunk once—only on the multicast  
VLAN. Although the IGMP leave and join message in the VLAN to which the subscriber port is  
assigned. These messages dynamically register for streams of multicast traffic in the multicast VLAN  
on the Layer 3 device. The access layer switch (Switch A) modifies the forwarding behavior to allow the  
traffic to be forwarded from the multicast VLAN to the subscriber port in a different VLAN, selectively  
allowing traffic to cross between two VLANs.  
IGMP reports are sent to the same MAC addresses as the multicast data. The Switch A CPU must capture  
all IGMP join and leave messages from receiver ports and forward them to the multicast VLAN of the  
source (uplink) port.  
Configuring MVR  
These sections include basic MVR configuration information:  
•
•
•
•
Default MVR Configuration, page 14-18  
MVR Configuration Guidelines and Limitations, page 14-18  
Configuring MVR Global Parameters, page 14-18  
Configuring MVR Interfaces, page 14-20  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring MVR  
Default MVR Configuration  
Table 14-5 shows the default MVR configuration.  
Table 14-5  
Default MVR Configuration  
Feature  
Default Setting  
MVR  
Disabled globally and per interface  
None configured  
Multicast addresses  
Query response time  
Multicast VLAN  
Mode  
0.5 second  
VLAN 1  
Compatible  
Interface (per port) default  
Immediate Leave  
Neither a receiver nor a source port  
Disabled on all ports  
MVR Configuration Guidelines and Limitations  
Follow these guidelines when configuring MVR:  
•
•
•
Receiver ports cannot be trunk ports. Receiver ports on a switch can be in different VLANs, but  
should not belong to the multicast VLAN.  
The maximum number of multicast entries that can be configured on a switch (that is, the maximum  
number of television channels that can be received) is 256.  
Each channel is one multicast stream destined for a unique IP multicast address. These IP addresses  
cannot alias between themselves or with the reserved IP multicast addresses (in the  
range 224.0.0.xxx).  
•
MVR does not support IGMPv3 messages.  
Note  
For complete syntax and usage information for the commands used in this section, see the command  
reference for this release.  
Configuring MVR Global Parameters  
You do not need to set the optional MVR parameters if you choose to use the default settings. If you do  
want to change the default parameters (except for the MVR VLAN), you must first enable MVR.  
Beginning in privileged EXEC mode, follow these steps to configure MVR parameters:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
mvr  
Enter global configuration mode.  
Enable MVR on the switch.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring MVR  
Command  
Purpose  
Step 3  
mvr group ip-address [count]  
Configure an IP multicast address on the switch or use the count parameter to  
configure a contiguous series of MVR group addresses (the range for count is  
1 to 256; the default is 1). Any multicast data sent to this address is sent to all  
source ports on the switch and all receiver ports that have elected to receive  
data on that multicast address. Each multicast address would correspond to  
one television channel.  
Note  
Each IP address translates to a multicast 48-bit MAC address. If an IP  
address being configured translates (aliases) to a previously  
configured MAC address or to any reserved multicast MAC addresses,  
the command fails.  
Step 4  
mvr querytime value  
mvr vlan vlan-id  
(Optional) Define the maximum time to wait for IGMP report memberships  
on a receiver port before removing the port from multicast group membership.  
The value is in units of tenths of a second. The range is from 1 to 100 and the  
default is 5 tenths or one-half second.  
Step 5  
Step 6  
(Optional) Specify the VLAN in which multicast data is received; all source  
ports must belong to this VLAN. The VLAN ID range is 1 to 4094. The  
default is VLAN 1.  
mvr mode {dynamic | compatible} (Optional) Specify the MVR mode of operation:  
•
•
dynamic—Allows dynamic MVR membership on source ports.  
compatible—Is compatible with Catalyst 3500 XL and Catalyst 2900 XL  
switches and does not support IGMP dynamic joins on source ports.  
The default is compatible mode.  
Return to privileged EXEC mode.  
Verify the configuration.  
Step 7  
Step 8  
end  
show mvr  
or  
show mvr members  
Step 9  
copy running-config  
startup-config  
(Optional) Save your entries in the configuration file.  
To return the switch to its default settings, use the no mvr [mode | group ip-address | querytime | vlan]  
global configuration commands.  
This example shows how to enable MVR, configure the MVR group address, set the query time to  
1 second (10 tenths), specify the MVR multicast VLAN as VLAN 22, set the MVR mode as dynamic,  
and verify the results:  
Switch(config)# mvr  
Switch(config)# mvr group 228.1.23.4  
Switch(config)# mvr querytime 10  
Switch(config)# mvr vlan 22  
Switch(config)# mvr mode dynamic  
Switch(config)# end  
Switch# show mvr  
MVR Running: TRUE  
MVR multicast vlan: 22  
MVR Max Multicast Groups: 256  
MVR Current multicast groups: 1  
MVR Global query response time: 10 (tenths of sec)  
MVR Mode: dynamic  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring MVR  
You can use the show mvr members privileged EXEC command to verify the MVR multicast group  
addresses on the switch.  
Configuring MVR Interfaces  
Beginning in privileged EXEC mode, follow these steps to configure MVR interfaces:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
configure terminal  
mvr  
Enter global configuration mode.  
Enable MVR on the switch.  
interface interface-id  
mvr type {source | receiver}  
Enter the port to configure and enter interface configuration mode.  
Configure an MVR port as one of these:  
•
source—Configure uplink ports that receive and send multicast data as  
source ports. Subscribers cannot be directly connected to source ports.  
All source ports on a switch belong to the single multicast VLAN.  
•
receiver—Configure a port as a receiver port if it is a subscriber port and  
should only receive multicast data. It does not receive data unless it  
becomes a member of the multicast group, either statically or by using  
IGMP leave and join messages. Receiver ports cannot belong to the  
multicast VLAN.  
The default configuration is as a non-MVR port. If you attempt to configure  
a non-MVR port with MVR characteristics, the operation fails.  
Step 5  
mvr vlan vlan-id group ip-address (Optional) Statically configure a port to receive multicast traffic sent to the  
multicast VLAN and the IP multicast address. A port statically configured as  
a member of a group remains a member of the group until statically removed.  
Note  
In compatible mode, this command applies to only receiver ports. In  
dynamic mode, it applies to receiver ports and source ports.  
Receiver ports can also dynamically join multicast groups by using IGMP  
join and leave messages.  
Step 6  
mvr immediate  
(Optional) Enable the Immediate Leave feature of MVR on the port.  
Note  
This command applies to only receiver ports and should only be  
enabled on receiver ports to which a single receiver device is  
connected.  
Step 7  
Step 8  
end  
Return to privileged EXEC mode.  
Verify the configuration.  
show mvr  
show mvr interface  
or  
show mvr members  
Step 9  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To return the interface to its default settings, use the no mvr [type | immediate | vlan vlan-id | group]  
interface configuration commands.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Displaying MVR Information  
This example shows how to configure a port as a receiver port, statically configure the port to receive  
multicast traffic sent to the multicast group address, configure Immediate Leave on the interface, and  
verify the results.  
Switch(config)# mvr  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# mvr type receiver  
Switch(config-if)# mvr vlan 22 group 228.1.23.4  
Switch(config-if)# mvr immediate  
Switch(config)# end  
Switch# show mvr interface gigabitethernet0/17  
Type: RECEIVER Status: ACTIVE Immediate Leave: ENABLED  
Displaying MVR Information  
You can display MVR information for the switch or for a specified interface. Beginning in privileged  
EXEC mode, use the commands in Table 14-6 to display MVR configuration:  
Table 14-6  
Commands for Displaying MVR Information  
show mvr  
Displays MVR status and values for the switch—whether MVR is enabled or disabled,  
the multicast VLAN, the maximum (256) and current (0 through 256) number of  
multicast groups, the query response time, and the MVR mode.  
show mvr interface [interface-id] Displays all MVR interfaces and their MVR configurations.  
[members [vlan vlan-id]]  
When a specific interface is entered, displays this information:  
•
•
Type—Receiver or Source  
Status—One of these:  
–
–
–
Active means the port is part of a VLAN.  
Up/Down means that the port is forwarding or nonforwarding.  
Inactive means that the port is not part of any VLAN.  
•
Immediate Leave—Enabled or Disabled  
If the members keyword is entered, displays all multicast group members on this port or,  
if a VLAN identification is entered, all multicast group members on the VLAN. The  
VLAN ID range is 1 to 4094.  
show mvr members [ip-address] Displays all receiver and source ports that are members of any IP multicast group or the  
specified IP multicast group IP address.  
Configuring IGMP Filtering and Throttling  
In some environments, for example, metropolitan or multiple-dwelling unit (MDU) installations, you  
might want to control the set of multicast groups to which a user on a switch port can belong. You can  
control the distribution of multicast services, such as IP/TV, based on some type of subscription or  
service plan. You might also want to limit the number of multicast groups to which a user on a switch  
port can belong.  
With the IGMP filtering feature, you can filter multicast joins on a per-port basis by configuring IP  
multicast profiles and associating them with individual switch ports. An IGMP profile can contain one  
or more multicast groups and specifies whether access to the group is permitted or denied. If an IGMP  
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Configuring IGMP Filtering and Throttling  
profile denying access to a multicast group is applied to a switch port, the IGMP join report requesting  
the stream of IP multicast traffic is dropped, and the port is not allowed to receive IP multicast traffic  
from that group. If the filtering action permits access to the multicast group, the IGMP report from the  
port is forwarded for normal processing.  
IGMP filtering controls only group specific query and membership reports, including join and leave  
reports. It does not control general IGMP queries. IGMP filtering has no relationship with the function  
that directs the forwarding of IP multicast traffic. The filtering feature operates in the same manner  
whether CGMP or MVR is used to forward the multicast traffic.  
You can also set the maximum number of IGMP groups that a Layer 2 interface can join.  
With the IGMP throttling feature, you can also set the maximum number of IGMP groups that a Layer 2  
interface can join. If the maximum number of IGMP groups is set, the IGMP snooping forwarding table  
contains the maximum number of entries, and the interface receives an IGMP join report, you can  
configure an interface to drop the IGMP report or to replace the randomly selected multicast entry with  
the received IGMP report.  
Note  
IGMPv3 join and leave messages are not supported on switches running IGMP filtering.  
These sections describe how to configure IGMP filtering and throttling:  
•
•
•
•
•
Default IGMP Filtering and Throttling Configuration, page 14-22  
Configuring IGMP Profiles, page 14-23 (optional)  
Applying IGMP Profiles, page 14-24 (optional)  
Setting the Maximum Number of IGMP Groups, page 14-25 (optional)  
Configuring the IGMP Throttling Action, page 14-25 (optional)  
Default IGMP Filtering and Throttling Configuration  
Table 14-7 shows the default IGMP filtering configuration.  
Table 14-7  
Default IGMP Filtering Configuration  
Feature  
Default Setting  
IGMP filters  
None applied  
IGMP Maximum number of IGMP groups  
IGMP profiles  
No maximum set  
None defined  
IGMP profile action  
Deny the range addresses  
When the maximum number of groups is in forwarding table, the default IGMP throttling action is to  
deny the IGMP report. For configuration guidelines, see the “Configuring the IGMP Throttling Action”  
section on page 14-25.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring IGMP Filtering and Throttling  
Configuring IGMP Profiles  
To configure an IGMP profile, use the ip igmp profile global configuration command with a profile  
number to create an IGMP profile and to enter IGMP profile configuration mode. From this mode, you  
can specify the parameters of the IGMP profile to be used for filtering IGMP join requests from a port.  
When you are in IGMP profile configuration mode, you can create the profile by using these commands:  
•
•
•
•
•
deny: Specifies that matching addresses are denied; this is the default condition.  
exit: Exits from igmp-profile configuration mode.  
no: Negates a command or sets its defaults.  
permit: Specifies that matching addresses are permitted.  
range: Specifies a range of IP addresses for the profile. You can enter a single IP address or a range  
with a start and an end address.  
The default is for the switch to have no IGMP profiles configured. When a profile is configured, if  
neither the permit nor deny keyword is included, the default is to deny access to the range of IP  
addresses.  
Beginning in privileged EXEC mode, follow these steps to create an IGMP profile:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ip igmp profile profile number  
Enter IGMP profile configuration mode, and assign a number to the  
profile you are configuring. The range is 1 to 4294967295.  
Step 3  
Step 4  
permit | deny  
(Optional) Set the action to permit or deny access to the IP multicast  
address. If no action is configured, the default for the profile is to deny  
access.  
range ip multicast address  
Enter the IP multicast address or range of IP multicast addresses to  
which access is being controlled. If entering a range, enter the low IP  
multicast address, a space, and the high IP multicast address.  
You can use the range command multiple times to enter multiple  
addresses or ranges of addresses.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
show ip igmp profile profile number  
copy running-config startup-config  
Verify the profile configuration.  
(Optional) Save your entries in the configuration file.  
To delete a profile, use the no ip igmp profile profile number global configuration command.  
To delete an IP multicast address or range of IP multicast addresses, use the no range ip multicast  
address IGMP profile configuration command.  
This example shows how to create IGMP profile 4 allowing access to the single IP multicast address and  
how to verify the configuration. If the action was to deny (the default), it would not appear in the show  
ip igmp profile output display.  
Switch(config)# ip igmp profile 4  
Switch(config-igmp-profile)# permit  
Switch(config-igmp-profile)# range 229.9.9.0  
Switch(config-igmp-profile)# end  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring IGMP Filtering and Throttling  
Switch# show ip igmp profile 4  
IGMP Profile 4  
permit  
range 229.9.9.0 229.9.9.0  
Applying IGMP Profiles  
To control access as defined in an IGMP profile, use the ip igmp filter interface configuration command  
to apply the profile to the appropriate interfaces. You can apply IGMP profiles to Layer 2 ports only. You  
cannot apply profiles to ports that belong to an EtherChannel port group. You can apply a profile to  
multiple interfaces, but each interface can only have one profile applied to it.  
Beginning in privileged EXEC mode, follow these steps to apply an IGMP profile to a switch port:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Enter interface configuration mode by entering the physical interface to  
configure. The interface must be a Layer 2 port that does not belong to  
an EtherChannel port group.  
Step 3  
ip igmp filter profile number  
Apply the specified IGMP profile to the interface. The profile number  
can be 1 to 4294967295.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify the configuration.  
show running configuration interface  
interface-id  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To remove a profile from an interface, use the no ip igmp filter profile number interface configuration  
command.  
This example shows how to apply IGMP profile 4 to a port and verify the configuration.  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# ip igmp filter 4  
Switch(config-if)# end  
Switch# show running-config interface gigabitethernet0/17  
Building configuration...  
Current configuration : 123 bytes  
!
interface gigabitethernet0/17  
no ip address  
shutdown  
snmp trap link-status  
ip igmp max-groups 25  
ip igmp filter 4  
end  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring IGMP Filtering and Throttling  
Setting the Maximum Number of IGMP Groups  
You can set the maximum number of IGMP groups that a Layer 2 interface can join by using the ip igmp  
max-groups interface configuration command. Use the no form of this command to set the maximum  
back to the default, which is no limit.  
You can use this command on an logical EtherChannel interface but cannot use it on ports that belong to  
an EtherChannel port group.  
Beginning in privileged EXEC mode, follow these steps to set the maximum number of IGMP groups in  
the forwarding table:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Enter interface configuration mode by entering the physical interface to  
configure. The interface can be a Layer 2 port that does not belong to an  
EtherChannel group or a EtherChannel interface.  
Step 3  
ip igmp max-groups number  
Set the maximum number of IGMP groups that the interface can join.  
The range is 0 to 4294967294. The default is to have no maximum set.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify the configuration.  
show running-configuration interface  
interface-id  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To remove the maximum group limitation and return to the default of no maximum, use the no ip igmp  
max-groups interface configuration command.  
This example shows how to limit to 25 the number of IGMP groups that an interface can join.  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# ip igmp max-groups 25  
Switch(config-if)# end  
Configuring the IGMP Throttling Action  
After you set the maximum number of IGMP groups that a Layer 2 interface can join, you can configure  
an interface to replace the existing group with the new group for which the IGMP report was received  
by using the ip igmp max-groups action replace interface configuration command. Use the no form of  
this command to return to the default, which is to drop the IGMP join report.  
Follow these guidelines when configuring the IGMP throttling action:  
•
You can use this command on a logical EtherChannel interface but cannot use it on ports that belong  
to an EtherChannel port group.  
•
When the maximum group limitation is set to the default (no maximum), entering the ip igmp  
max-groups action {deny | replace} command has no effect.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Configuring IGMP Filtering and Throttling  
•
If you configure the throttling action and set the maximum group limitation after an interface has  
added multicast entries to the forwarding table, the forwarding-table entries are either aged out or  
removed, depending on the throttling action.  
–
If you configure the throttling action as deny, the entries that were previously in the forwarding  
table are not removed but are aged out. After these entries are aged out and the maximum  
number of entries is in the forwarding table, the switch drops the next IGMP report received on  
the interface.  
–
If you configure the throttling action as replace, the entries that were previously in the  
forwarding table are removed. When the maximum number of entries is in the forwarding table,  
the switch the switch replaces a randomly selected entry with the received IGMP report.  
To prevent the switch from removing the forwarding-table entries, you can configure the IGMP  
throttling action before an interface adds entries to the forwarding table.  
Beginning in privileged EXEC mode, follow these steps to configure the throttling action when the  
maximum number of entries is in the forwarding table:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Enter interface configuration mode, and enter the physical interface to  
configure. The interface can be a Layer 2 port that does not belong to an  
EtherChannel group or an EtherChannel interface. The interface cannot  
be a trunk port.  
Step 3  
ip igmp max-groups action {deny |  
replace}  
When an interface receives an IGMP report and the maximum number  
of entries is in the forwarding table, specify the action that the interface  
takes:  
•
•
deny—Drop the report.  
replace—Replace the existing group with the new group for which  
the IGMP report was received.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify the configuration.  
show running-config interface  
interface-id  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return to the default action of dropping the report, use the no ip igmp max-groups action interface  
configuration command.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Displaying IGMP Filtering and Throttling Configuration  
Displaying IGMP Filtering and Throttling Configuration  
You can display IGMP profile characteristics, and you can display the IGMP profile and maximum group  
configuration for all interfaces on the switch or for a specified interface. You can also display the IGMP  
throttling configuration for all interfaces on the switch or for a specified interface.  
Use the privileged EXEC commands in Table 14-8 to display IGMP filtering and throttling  
configuration:  
Table 14-8  
Commands for Displaying IGMP Filtering and Throttling Configuration  
Command  
Purpose  
how ip igmp profile [profile number]  
Displays the specified IGMP profile or all the IGMP profiles defined on the  
switch.  
show running-configuration [interface  
interface-id]  
Displays the configuration of the specified interface or the configuration of all  
interfaces on the switch, including (if configured) the maximum number of  
IGMP groups to which an interface can belong and the IGMP profile applied to  
the interface.  
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Chapter 14 Configuring IGMP Snooping and MVR  
Displaying IGMP Filtering and Throttling Configuration  
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C H A P T E R  
15  
Configuring Port-Based Traffic Control  
This chapter describes how to configure the port-based traffic control features on your Cisco Systems  
Intelligent Gigabit Ethernet Switch Module.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
This chapter consists of these sections:  
•
•
•
•
Configuring Storm Control, page 15-1  
Configuring Protected Ports, page 15-3  
Configuring Port Security, page 15-4  
Displaying Port-Based Traffic Control Settings, page 15-11  
Configuring Storm Control  
These sections include storm control configuration information and procedures:  
•
•
•
Understanding Storm Control, page 15-1  
Default Storm Control Configuration, page 15-2  
Configuring Storm Control and Threshold Levels, page 15-2  
Understanding Storm Control  
Storm control prevents traffic on a LAN from being disrupted by a broadcast, multicast, or unicast storm  
on a port. A LAN storm occurs when packets flood the LAN, creating excessive traffic and degrading  
network performance. Errors in the protocol-stack implementation, mistakes in network configuration,  
or users issuing a denial-of-service attack can cause a storm.  
Storm control is configured for the switch as a whole but operates on a per-port basis. By default, storm  
control is disabled.  
Storm control uses rising and falling thresholds to block and then restore the forwarding of broadcast,  
unicast, or multicast packets. You can also set the switch to shut down the port when the rising threshold  
is reached.  
Storm control uses a bandwidth-based method to measure traffic activity.  
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Chapter 15 Configuring Port-Based Traffic Control  
Configuring Storm Control  
The thresholds can either be expressed as a percentage of the total available bandwidth that can be used  
by the broadcast, multicast, or unicast traffic, or as the rate at which the interface receives multicast,  
broadcast, or unicast traffic.  
When a switch uses the bandwidth-based method, the rising threshold is the percentage of total available  
bandwidth associated with multicast, broadcast, or unicast traffic before forwarding is blocked. The  
falling threshold is the percentage of total available bandwidth below which the switch resumes normal  
forwarding. In general, the higher the level, the less effective the protection against broadcast storms.  
When a switch uses traffic rates as the threshold values, the rising and falling thresholds are in packets  
per second. The rising threshold is the rate at which multicast, broadcast, and unicast traffic is received  
before forwarding is blocked. The falling threshold is the rate below which the switch resumes normal  
forwarding. In general, the higher the rate, the less effective the protection against broadcast storms.  
Default Storm Control Configuration  
By default, broadcast, multicast, and unicast storm control is disabled on the switch. The default action  
is to filter traffic and to not send an SNMP trap.  
Configuring Storm Control and Threshold Levels  
Beginning in privileged EXEC mode, follow these steps to configure storm control and threshold levels:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the port to configure, and enter interface configuration  
mode.  
Step 3  
storm-control {broadcast | multicast |  
unicast} level {level [level-low] | pps pps  
[pps-low]}  
Configure broadcast, multicast, or unicast storm control.  
The keywords have these meanings:  
•
•
For level, specify the rising threshold level for broadcast,  
multicast, or unicast traffic as a percentage of the bandwidth.  
The storm control action occurs when traffic utilization reaches  
this level.  
(Optional) For level-low, specify the falling threshold level as a  
percentage of the bandwidth. This value must be less than the  
rising supression value.The normal transmission restarts (if the  
action is filtering) when traffic drops below this level.  
•
•
For pps pps, specify the rising threshold level for broadcast,  
multicast, or unicast traffic in packets per second. The storm  
control action occurs when traffic reaches this level.  
(Optional) For pps-low, specify the falling threshold level in  
packets per second that can be less than or equal to the rising  
threshold level. The normal transmission restarts (if the action is  
filtering) when traffic drops below this level.  
For pps and pps-low, the range is from 0 to 4294967295.  
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Chapter 15 Configuring Port-Based Traffic Control  
Configuring Protected Ports  
Command  
Purpose  
Step 4  
storm-control action {shutdown | trap}  
Specify the action to be taken when a storm is detected. The default  
is to filter out the traffic and not to send traps.  
•
Select the shutdown keyword to error-disable the port during a  
storm.  
•
Select the trap keyword to generate an SNMP trap when a storm  
is detected.  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show storm-control [interface] [{broadcast Verify your entries.  
| history | multicast | unicast}]  
Step 7  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable storm control, use the no storm-control broadcast level, the no storm-control multicast  
level, or the no storm-control unicast level interface configuration command.  
This example shows how to enable broadcast address storm control on a port to a level of 20 percent.  
When the broadcast traffic exceeds the configured level of 20 percent of the available bandwidth of the  
port within the traffic-storm-control interval, the switch drops all broadcast traffic until the end of the  
traffic-storm-control interval:  
Switch# configure terminal  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# storm-control broadcast level 20  
If you configure the action to be taken when a packet storm is detected as shutdown (the port is  
error-disabled during a storm), you must use the no shutdown interface configuration command to bring  
the interface out of this state. If you do not specify the shutdown action, specify the action as trap (the  
switch generates a trap when a storm is detected).  
Configuring Protected Ports  
Some applications require that no traffic be forwarded between ports on the same switch so that one  
neighbor does not see the traffic generated by another neighbor. In such an environment, the use of  
protected ports ensures that there is no exchange of unicast, broadcast, or multicast traffic between these  
ports on the switch.  
Protected ports have these features:  
•
A protected port does not forward any traffic (unicast, multicast, or broadcast) to any other port that  
is also a protected port. Data traffic cannot be forwarded between protected ports at Layer 2; only  
control traffic, such as PIM packets, is forwarded because these packets are processed by the CPU  
and forwarded in software. All data traffic passing between protected ports must be forwarded  
through a Layer 3 device.  
•
•
Forwarding behavior between a protected port and a nonprotected port proceeds as usual.  
Protected ports are supported on IEEE 802.1Q trunks.  
The default is to have no protected ports defined.  
You can configure protected ports on a physical interface or an EtherChannel group. When you enable  
protected ports for a port channel, it is enabled for all ports in the port-channel group.  
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Chapter 15 Configuring Port-Based Traffic Control  
Configuring Port Security  
Beginning in privileged EXEC mode, follow these steps to define a port as a protected port:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to configure, and enter interface  
configuration mode.  
Step 3  
Step 4  
Step 5  
Step 6  
switchport protected  
Configure the interface to be a protected port.  
Return to privileged EXEC mode.  
end  
show interfaces interface-id switchport  
copy running-config startup-config  
Verify your entries.  
(Optional) Save your entries in the configuration file.  
To disable protected port, use the no switchport protected interface configuration command.  
This example shows how to configure a port as a protected port:  
Switch# configure terminal  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# switchport protected  
Switch(config-if)# end  
Configuring Port Security  
Note  
You cannot configure port security on the internal 100 Mbps management module ports.  
You can use the port security feature to restrict input to an interface by limiting and identifying MAC  
addresses of the stations allowed to access the port. When you assign secure MAC addresses to a secure  
port, the port does not forward packets with source addresses outside the group of defined addresses.  
This section includes information about these topics:  
•
•
•
•
•
Understanding Port Security, page 15-4  
Default Port Security Configuration, page 15-6  
Port Security Configuration Guidelines, page 15-6  
Enabling and Configuring Port Security, page 15-7  
Enabling and Configuring Port Security Aging, page 15-9  
Understanding Port Security  
This section includes information about:  
•
•
Secure MAC Addresses, page 15-5  
Security Violations, page 15-5  
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Chapter 15 Configuring Port-Based Traffic Control  
Configuring Port Security  
Secure MAC Addresses  
You can configure these types of secure MAC addresses:  
•
Static secure MAC addresses—These are manually configured by using the switchport  
port-security mac-address mac-address interface configuration command, stored in the address  
table, and added to the switch running configuration.  
•
•
Dynamic secure MAC addresses—These are dynamically learned, stored only in the address table,  
and removed when the switch restarts.  
Sticky secure MAC addresses—These can be dynamically learned or manually configured, stored in  
the address table, and added to the running configuration. If these addresses are saved in the  
configuration file, the interface does not need to dynamically relearn them when the switch restarts.  
Although sticky secure addresses can be manually configured, we do not recommend it.  
You can configure an interface to convert the dynamic MAC addresses to sticky secure MAC addresses  
and to add them to the running configuration by enabling sticky learning. To enable sticky learning, enter  
the switchport port-security mac-address sticky interface configuration command. When you enter  
this command, the interface converts all the dynamic secure MAC addresses, including those that were  
dynamically learned before sticky learning was enabled, to sticky secure MAC addresses.  
The sticky secure MAC addresses do not automatically become part of the configuration file, which is  
the startup configuration used each time the switch restarts. If you save the sticky secure MAC addresses  
in the configuration file, when the switch restarts, the interface does not need to relearn these addresses.  
If you do not save the configuration, they are lost.  
If sticky learning is disabled, the sticky secure MAC addresses are converted to dynamic secure  
addresses and are removed from the running configuration.  
A secure port can have from 1 to 132 associated secure addresses. The total number of available secure  
addresses on the switch is 1024.  
Security Violations  
It is a security violation when one of these situations occurs:  
•
The maximum number of secure MAC addresses have been added to the address table, and a station  
whose MAC address is not in the address table attempts to access the interface.  
•
An address learned or configured on one secure interface is seen on another secure interface in the  
same VLAN.  
You can configure the interface for one of three violation modes, based on the action to be taken if a  
violation occurs:  
•
protect—When the number of secure MAC addresses reaches the limit allowed on the port, packets  
with unknown source addresses are dropped until you remove a sufficient number of secure MAC  
addresses or increase the number of maximum allowable addresses. You are not notified that a  
security violation has occurred.  
•
restrict—When the number of secure MAC addresses reaches the limit allowed on the port, packets  
with unknown source addresses are dropped until you remove a sufficient number of secure MAC  
addresses or increase the number of maximum allowable addresses. In this mode, you are notified  
that a security violation has occurred. Specifically, an SNMP trap is sent, a syslog message is  
logged, and the violation counter increments.  
•
shutdown—In this mode, a port security violation causes the interface to immediately become  
error-disabled, and turns off the port LED. It also sends an SNMP trap, logs a syslog message, and  
increments the violation counter. When a secure port is in the error-disabled state, you can bring it  
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Chapter 15 Configuring Port-Based Traffic Control  
Configuring Port Security  
out of this state by entering the errdisable recovery cause psecure-violation global configuration  
command, or you can manually re-enable it by entering the shutdown and no shutdown interface  
configuration commands. This is the default mode.  
Table 15-1 shows the violation mode and the actions taken when you configure an interface for port  
security.  
Table 15-1  
Security Violation Mode Actions  
Violation  
counter  
increments  
Traffic is  
Violation Mode forwarded1  
Sends SNMP  
trap  
Sends syslog  
message  
Displays error  
message2  
Shuts down port  
protect  
No  
No  
No  
No  
No  
No  
No  
No  
No  
No  
No  
Yes  
restrict  
Yes  
Yes  
Yes  
Yes  
Yes  
Yes  
shutdown  
1. Packets with unknown source addresses are dropped until you remove a sufficient number of secure MAC addresses.  
2. The switch will return an error message if you manually configure an address that would cause a security violation.  
Default Port Security Configuration  
Table 15-2 shows the default port security configuration for an interface.  
Table 15-2  
Default Port Security Configuration  
Feature  
Default Setting  
Disabled.  
Port security  
Maximum number of secure MAC addresses One.  
Violation mode  
Shutdown.  
Disabled.  
Sticky address learning  
Port security aging  
Disabled. Aging time is 0. When enabled, the default  
type is absolute.  
Port Security Configuration Guidelines  
Follow these guidelines when configuring port security:  
•
•
•
•
•
•
Port security can only be configured on static access ports.  
A secure port cannot be a dynamic access port or a trunk port.  
A secure port cannot be a destination port for Switched Port Analyzer (SPAN).  
A secure port cannot belong to a Fast EtherChannel or Gigabit EtherChannel port group.  
You cannot configure static secure or sticky secure MAC addresses on a voice VLAN.  
When you enable port security on an interface that is also configured with a voice VLAN, you must  
set the maximum allowed secure addresses on the port to at least two plus the maximum number of  
secure addresses allowed on the access VLAN. When the port is connected to a Cisco IP phone, the  
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Chapter 15 Configuring Port-Based Traffic Control  
Configuring Port Security  
IP phone requires up to two MAC addresses. The address of the IP phone is learned on the voice  
VLAN, and it might or might not be learned on the access VLAN. Connecting a PC to the IP phone  
requires additional MAC addresses  
•
•
If any type of port security is enabled on the access VLAN, dynamic port security is automatically  
enabled on the voice VLAN.  
When a voice VLAN is configured on a secure port that is also configured as a sticky secure port,  
all addresses seen on the voice VLAN are learned as dynamic secure addresses, and all addresses  
seen on the access VLAN (to which the port belongs) are learned as sticky secure addresses.  
•
•
•
You cannot configure port security on a per-VLAN basis.  
The switch does not support port security aging of sticky secure MAC addresses.  
The protect and restrict options cannot be simultaneously enabled on an interface.  
Table 15-3 summarizes port security compatibility with other features configured on a port.  
Table 15-3  
Port Security Compatibility with Other Switch Features  
Type of Port  
DTP1 port2  
Trunk port  
Compatible with Port Security  
No  
No  
Dynamic-access port3  
No  
SPAN source port  
Yes  
No  
SPAN destination port  
EtherChannel  
No  
Protected port  
Yes  
Yes  
Yes  
IEEE 802.1x port  
Voice VLAN port4  
1. DTP = Dynamic Trunking Protocol  
2. A port configured with the switchport mode dynamic interface configuration command.  
3. A VLAN Query Protocol (VQP) port configured with the switchport access vlan dynamic interface  
configuration command.  
4. You must set the maximum allowed secure addresses on the port to two plus the maximum  
number of secure addresses allowed on the access VLAN.  
Enabling and Configuring Port Security  
Beginning in privileged EXEC mode, follow these steps to restrict input to an interface by limiting and  
identifying MAC addresses of the stations allowed to access the port:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to configure, and enter interface configuration  
mode.  
Step 3  
switchport mode access  
Set the interface mode as access; an interface in the default mode  
(dynamic desirable) cannot be configured as a secure port.  
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Configuring Port Security  
Command  
Purpose  
Step 4  
switchport port-security  
Enable port security on the interface.  
Step 5  
switchport port-security maximum  
value  
(Optional) Set the maximum number of secure MAC addresses for the  
interface. The range is 1 to 132; the default is 1.  
Step 6  
switchport port-security violation  
{protect | restrict | shutdown}  
(Optional) Set the violation mode, the action to be taken when a security  
violation is detected, as one of these:  
•
protect—When the number of secure MAC addresses reaches the  
limit allowed on the port, packets with unknown source addresses  
are dropped until you remove a sufficient number of secure MAC  
addresses or increase the number of maximum allowable addresses.  
You are not notified that a security violation has occurred.  
•
restrict—When the number of secure MAC addresses reaches the  
limit allowed on the port, packets with unknown source addresses  
are dropped until you remove a sufficient number of secure MAC  
addresses or increase the number of maximum allowable addresses.  
In this mode, you are notified that a security violation has occurred.  
Specifically, an SNMP trap is sent, a syslog message is logged, and  
the violation counter increments.  
•
shutdown—In this mode, a port security violation causes the  
interface to immediately become error-disabled, and turns off the  
port LED. It also sends an SNMP trap, logs a syslog message, and  
increments the violation counter.  
Note  
When a secure port is in the error-disabled state, you can bring  
it out of this state by entering the errdisable recovery cause  
psecure-violation global configuration command, or you can  
manually re-enable it by entering the shutdown and no  
shutdown interface configuration commands.  
Step 7  
switchport port-security mac-address  
mac-address  
(Optional) Enter a static secure MAC address for the interface, repeating  
the command as many times as necessary. You can use this command to  
enter the maximum number of secure MAC addresses. If you configure  
fewer secure MAC addresses than the maximum, the remaining MAC  
addresses are dynamically learned.  
Note  
If you enable sticky learning after you enter this command, the  
secure addresses that were dynamically learned are converted to  
sticky secure MAC addresses and are added to the running  
configuration.  
Step 8  
switchport port-security mac-address  
sticky  
(Optional) Enable sticky learning on the interface.  
Step 9  
end  
Return to privileged EXEC mode.  
Verify your entries.  
Step 10  
Step 11  
show port-security  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 15 Configuring Port-Based Traffic Control  
Configuring Port Security  
To return the interface to the default condition as not a secure port, use the no switchport port-security  
interface configuration command. If you enter this command when sticky learning is enabled, the sticky  
secure addresses remain part of the running configuration but are removed from the address table. All  
addresses are now dynamically learned.  
To return the interface to the default number of secure MAC addresses, use the no switchport  
port-security maximum value interface configuration command.  
To return the violation mode to the default condition (shutdown mode), use the no switchport  
port-security violation {protect | restrict} interface configuration command.  
To disable sticky learning on an interface, use the no switchport port-security mac-address sticky  
interface configuration command. The interface converts the sticky secure MAC addresses to dynamic  
secure addresses.  
To delete a static secure MAC address from the address table, use the clear port-security configured  
address mac-address privileged EXEC command. To delete all the static secure MAC addresses on an  
interface, use the clear port-security configured interface interface-id privileged EXEC command.  
To delete a dynamic secure MAC address from the address table, use the clear port-security dynamic  
address mac-address privileged EXEC command. To delete all the dynamic addresses on an interface,  
use the clear port-security dynamic interface interface-id privileged EXEC command.  
To delete a sticky secure MAC addresses from the address table, use the clear port-security sticky  
address mac-address privileged EXEC command. To delete all the sticky addresses on an interface, use  
the clear port-security sticky interface interface-id privileged EXEC command.  
This example shows how to enable port security on a port and to set the maximum number of secure  
addresses to 50. The violation mode is the default, no static secure MAC addresses are configured, and  
sticky learning is enabled.  
Switch# configure terminal  
Enter configuration commands, one per line. End with CNTL/Z.  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# switchport mode access  
Switch(config-if)# switchport port-security  
Switch(config-if)# switchport port-security maximum 50  
Switch(config-if)# switchport port-security mac-address sticky  
Switch(config-if)# end  
This example shows how to configure a static secure MAC address on a port and enable sticky learning:  
Switch# configure terminal  
Enter configuration commands, one per line. End with CNTL/Z.  
Switch(config)# interface gigabitethernet0/18  
Switch(config-if)# switchport mode access  
Switch(config-if)# switchport port-security  
Switch(config-if)# switchport port-security mac-address 0000.02000.0004  
Switch(config-if)# switchport port-security mac-address sticky  
Switch(config-if)# end  
Enabling and Configuring Port Security Aging  
You can use port security aging to set the aging time for static and dynamic secure addresses on a port.  
Two types of aging are supported per port:  
•
•
Absolute—The secure addresses on the port are deleted after the specified aging time.  
Inactivity—The secure addresses on the port are deleted only if the secure addresses are inactive for  
the specified aging time.  
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Configuring Port Security  
Use this feature to remove and add PCs on a secure port without manually deleting the existing secure  
MAC addresses and to still limit the number of secure addresses on a port. You can enable or disable the  
aging of statically configured secure addresses on a per-port basis.  
Beginning in privileged EXEC mode, follow these steps to configure port security aging:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the port on which you want to enable port security aging, and enter  
interface configuration mode.  
Note  
The switch does not support port security aging of sticky secure  
addresses.  
Step 3  
switchport port-security aging  
Enable or disable static aging for the secure port, or set the aging time or  
{static | time time | type {absolute | type.  
inactivity}}  
Enter static to enable aging for statically configured secure addresses on this  
port.  
For time, specify the aging time for this port. The valid range is from 0 to  
1440 minutes. If the time is equal to 0, aging is disabled for this port.  
For type, select one of these keywords:  
•
absolute—Sets the aging type as absolute aging. All the secure  
addresses on this port age out after the specified time (minutes) lapses  
and are removed from the secure address list.  
Note  
•
The absolute aging time could vary by 1 minute, depending on the  
sequence of the system timer.  
inactivity—Sets the aging type as inactivity aging. The secure addresses  
on this port age out only if there is no data traffic from the secure source  
addresses for the specified time period.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show port-security [interface  
interface-id] [address]  
Step 6  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To disable port security aging for all secure addresses on a port, use the no switchport port-security  
aging time interface configuration command. To disable aging for only statically configured secure  
addresses, use the no switchport port-security aging static interface configuration command.  
This example shows how to set the aging time as 2 hours for the secure addresses on a port:  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# switchport port-security aging time 120  
This example shows how to set the aging time as 2 minutes for the inactivity aging type with aging  
enabled for the configured secure addresses on the interface:  
Switch(config-if)# switchport port-security aging time 2  
Switch(config-if)# switchport port-security aging type inactivity  
Switch(config-if)# switchport port-security aging static  
You can verify the previous commands by entering the show port-security interface interface-id  
privileged EXEC command.  
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Chapter 15 Configuring Port-Based Traffic Control  
Displaying Port-Based Traffic Control Settings  
Displaying Port-Based Traffic Control Settings  
The show interfaces interface-id switchport privileged EXEC command displays (among other  
characteristics) the interface traffic suppression and control configuration. The show storm-control and  
show port-security privileged EXEC commands display those features.  
To display traffic control information, use one or more of the privileged EXEC commands in Table 15-4.  
Table 15-4  
Commands for Displaying Traffic Control Status and Configuration  
Command  
Purpose  
show interfaces [interface-id] switchport  
Displays the administrative and operational status of all switching  
(nonrouting) ports or the specified port, including port blocking and  
port protection settings.  
show storm-control [interface-id] [broadcast |  
multicast | unicast]  
Displays storm control suppression levels set on all interfaces or the  
specified interface for the specified traffic type or for broadcast traffic  
if no traffic type is entered.  
show port-security [interface interface-id]  
Displays port security settings for the switch or for the specified  
interface, including the maximum allowed number of secure MAC  
addresses for each interface, the number of secure MAC addresses on  
the interface, the number of security violations that have occurred, and  
the violation mode.  
show port-security [interface interface-id] address Displays all secure MAC addresses configured on all switch interfaces  
or on a specified interface with aging information for each address.  
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Chapter 15 Configuring Port-Based Traffic Control  
Displaying Port-Based Traffic Control Settings  
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C H A P T E R  
16  
Configuring UDLD  
This chapter describes how to configure the UniDirectional Link Detection (UDLD) protocol on your  
Cisco Systems Intelligent Gigabit Ethernet Switch Module.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
This chapter consists of these sections:  
•
•
•
Understanding UDLD, page 16-1  
Configuring UDLD, page 16-4  
Displaying UDLD Status, page 16-7  
Understanding UDLD  
UDLD is a Layer 2 protocol that enables devices connected through fiber-optic or twisted-pair Ethernet  
cables to monitor the physical configuration of the cables and detect when a unidirectional link exists.  
All connected devices must support UDLD for the protocol to successfully identify and disable  
unidirectional links. When UDLD detects a unidirectional link, it administratively shuts down the  
affected port and alerts you. Unidirectional links can cause a variety of problems, including  
spanning-tree topology loops.  
Modes of Operation  
UDLD supports two modes of operation: normal (the default) and aggressive. In normal mode, UDLD  
can detect unidirectional links due to misconnected interfaces on fiber-optic connections. In aggressive  
mode, UDLD can also detect unidirectional links due to one-way traffic on fiber-optic and twisted-pair  
links and to misconnected interfaces on fiber-optic links.  
In normal and aggressive modes, UDLD works with the Layer 1 mechanisms to determine the physical  
status of a link. At Layer 1, autonegotiation takes care of physical signaling and fault detection. UDLD  
performs tasks that autonegotiation cannot perform, such as detecting the identities of neighbors and  
shutting down misconnected interfaces. When you enable both autonegotiation and UDLD, the Layer 1  
and Layer 2 detections work together to prevent physical and logical unidirectional connections and the  
malfunctioning of other protocols.  
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Chapter 16 Configuring UDLD  
Understanding UDLD  
A unidirectional link occurs whenever traffic sent by a local device is received by its neighbor but traffic  
from the neighbor is not received by the local device.  
In normal mode, UDLD detects a unidirectional link when fiber strands in a fiber-optic interface are  
misconnected and the Layer 1 mechanisms do not detect this misconnection. If the interfaces are  
connected correctly but the traffic is one way, UDLD does not detect the unidirectional link because the  
Layer 1 mechanism, which is supposed to detect this condition, does not do so. In case, the logical link  
is considered undetermined, and UDLD does not disable the interface.  
When UDLD is in normal mode, if one of the fiber strands in a pair is disconnected and autonegotiation  
is active, the link does not stay up because the Layer 1 mechanisms did not detect a physical problem  
with the link. In this case, UDLD does not take any action, and the logical link is considered  
undetermined.  
In aggressive mode, UDLD detects a unidirectional link by using the previous detection methods. UDLD  
in aggressive mode can also detect a unidirectional link on a point-to-point link on which no failure  
between the two devices is allowed. It can also detect a unidirectional link when one of these problems  
exists:  
•
•
•
On fiber-optic or twisted-pair links, one of the interfaces cannot send or receive traffic.  
On fiber-optic or twisted-pair links, one of the interfaces is down while the other is up.  
One of the fiber strands in the cable is disconnected.  
In these cases, UDLD shuts down the affected interface.  
In a point-to-point link, UDLD hello packets can be considered as a heart beat whose presence  
guarantees the health of the link. Conversely, the loss of the heart beat means that the link must be shut  
down if it is not possible to re-establish a bidirectional link.  
If both fiber strands in a cable are working normally from a Layer 1 perspective, UDLD in aggressive  
mode determines whether those fiber strands are connected correctly and whether traffic is flowing  
bidirectionally between the correct neighbors. This check cannot be performed by autonegotiation  
because autonegotiation operates at Layer 1.  
Methods to Detect Unidirectional Links  
UDLD operates by using two mechanisms:  
•
Neighbor database maintenance  
UDLD learns about other UDLD-capable neighbors by periodically sending a hello packet (also  
called an advertisement or probe) on every active interface to keep each device informed about its  
neighbors.  
When the switch receives a hello message, it caches the information until the age time (hold time or  
time-to-live) expires. If the switch receives a new hello message before an older cache entry ages,  
the switch replaces the older entry with the new one.  
Whenever an interface is disabled and UDLD is running, whenever UDLD is disabled on an  
interface, or whenever the switch is reset, UDLD clears all existing cache entries for the interfaces  
affected by the configuration change. UDLD sends at least one message to inform the neighbors to  
flush the part of their caches affected by the status change. The message is intended to keep the  
caches synchronized.  
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Chapter 16 Configuring UDLD  
Understanding UDLD  
•
Event-driven detection and echoing  
UDLD relies on echoing as its detection mechanism. Whenever a UDLD device learns about a new  
neighbor or receives a resynchronization request from an out-of-sync neighbor, it restarts the  
detection window on its side of the connection and sends echo messages in reply. Because this  
behavior is the same on all UDLD neighbors, the sender of the echoes expects to receive an echo in  
reply.  
If the detection window ends and no valid reply message is received, the link might shut down,  
depending on the UDLD mode. When UDLD is in normal mode, the link might be considered  
undetermined and might not be shut down. When UDLD is in aggressive mode, the link is  
considered unidirectional, and the interface is shut down.  
If UDLD in normal mode is in the advertisement or in the detection phase and all the neighbor cache  
entries are aged out, UDLD restarts the link-up sequence to resynchronize with any potentially  
out-of-sync neighbors.  
If you enable aggressive mode when all the neighbors of a port have aged out either in the advertisement  
or in the detection phase, UDLD restarts the link-up sequence to resynchronize with any potentially  
out-of-sync neighbor. UDLD shuts down the port if, after the fast train of messages, the link state is still  
undetermined.  
Figure 16-1 shows an example of a unidirectional link condition.  
Figure 16-1  
UDLD Detection of a Unidirectional Link  
Switch A  
TX  
RX  
Switch B successfully  
receives traffic from  
Switch A on this port.  
However, Switch A does not receive traffic  
from Switch B on the same port. If UDLD  
is in aggressive mode, it detects the  
problem and disables the port. If UDLD is  
in normal mode, the logical link is  
considered undetermined, and UDLD  
does not disable the interface.  
TX  
RX  
Switch B  
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Chapter 16 Configuring UDLD  
Configuring UDLD  
Configuring UDLD  
This section describes how to configure UDLD on your switch. It contains this configuration  
information:  
•
•
•
•
•
Default UDLD Configuration, page 16-4  
Configuration Guidelines, page 16-4  
Enabling UDLD Globally, page 16-5  
Enabling UDLD on an Interface, page 16-6  
Resetting an Interface Shut Down by UDLD, page 16-6  
Default UDLD Configuration  
Table 16-1 shows the default UDLD configuration.  
Table 16-1  
Default UDLD Configuration  
Feature  
Default Setting  
UDLD global enable state  
Globally disabled  
UDLD per-interface enable state for fiber-optic media  
Disabled on all Ethernet fiber-optic interfaces  
Disabled on all 1000BASE-TX interfaces  
UDLD per-interface enable state for twisted-pair (copper)  
media  
UDLD aggressive mode  
Disabled  
Configuration Guidelines  
These are the UDLD configuration guidelines:  
•
•
A UDLD-capable interface also cannot detect a unidirectional link if it is connected to a  
UDLD-incapable port of another switch.  
When configuring the mode (normal or aggressive), make sure that the same mode is configured on  
both sides of the link.  
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Configuring UDLD  
Enabling UDLD Globally  
Beginning in privileged EXEC mode, follow these steps to enable UDLD in the aggressive or normal  
mode and to set the configurable message timer on all fiber-optic interfaces on the switch:  
Command  
configure terminal  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
udld {aggressive | enable | message time Specify the UDLD mode of operation:  
message-timer-interval}  
•
aggressive—Enables UDLD in aggressive mode on all fiber-optic  
interfaces.  
•
enable—Enables UDLD in normal mode on all fiber-optic  
interfaces on the switch. UDLD is disabled by default.  
An individual interface configuration overrides the setting of the  
udld enable global configuration command.  
For more information about aggressive and normal modes, see the  
“Modes of Operation” section on page 16-1.  
•
message time message-timer-interval—Configures the period of  
time between UDLD probe messages on ports that are in the  
advertisement phase and are determined to be bidirectional. The  
range is from 7 to 90 seconds.  
Note  
This command affects fiber-optic interfaces only. Use the udld  
interface configuration command to enable UDLD on other  
interface types. For more information, see the “Enabling UDLD  
on an Interface” section on page 16-6.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show udld  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable UDLD globally, use the no udld enable global configuration command to disable normal  
mode UDLD on all fiber-optic ports. Use the no udld aggressive global configuration command to  
disable aggressive mode UDLD on all fiber-optic ports.  
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Chapter 16 Configuring UDLD  
Configuring UDLD  
Enabling UDLD on an Interface  
Beginning in privileged EXEC mode, follow these steps to enable UDLD in the aggressive or normal  
mode on an interface:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to be enabled for UDLD, and enter interface  
configuration mode.  
Step 3  
udld port [aggressive]  
Specify the UDLD mode of operation:  
•
(Optional) aggressive— Enables UDLD in aggressive mode on the  
specified interface. UDLD is disabled by default.  
If you do not enter the aggressive keyword, the switch enables  
UDLD in normal mode.  
On a fiber-optic interface, this command overrides the udld enable  
global configuration command setting.  
For more information about aggressive and normal modes, see the  
“Modes of Operation” section on page 16-1.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show udld interface-id  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable UDLD on a non-fiber-optic interface, use the no udld port interface configuration command.  
Note  
On fiber-optic interfaces, the no udld port command reverts the interface configuration to the udld  
enable global configuration command setting.  
Use the no udld port interface configuration command to disable UDLD on a fiber-optic interface  
Resetting an Interface Shut Down by UDLD  
Beginning in privileged EXEC mode, follow these steps to reset all interfaces shut down by UDLD:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
udld reset  
Reset all interfaces shut down by UDLD.  
Verify your entries.  
show udld  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 16 Configuring UDLD  
Displaying UDLD Status  
You can also bring up the interface by using these commands:  
•
•
•
•
The shutdown interface configuration command followed by the no shutdown interface  
configuration command restarts the disabled interface.  
The no udld {aggressive | enable} global configuration command followed by the udld  
{aggressive | enable} global configuration command re-enables UDLD globally.  
The no udld port interface configuration command followed by the udld port [aggressive]  
interface configuration command re-enables UDLD on the specified interface.  
The errdisable recovery cause udld global configuration command enables the timer to  
automatically recover from the UDLD error-disabled state, and the errdisable recovery interval  
interval global configuration command specifies the time to recover from the UDLD error-disabled  
state.  
Displaying UDLD Status  
To display the UDLD status for the specified interface or for all interfaces, use the show udld  
[interface-id] privileged EXEC command.  
For detailed information about the fields in the display, see the command reference for this release.  
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Displaying UDLD Status  
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17  
Configuring CDP  
This chapter describes how to configure Cisco Discovery Protocol (CDP) on your Cisco Systems  
Intelligent Gigabit Ethernet Switch Module.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release and the Cisco IOS Configuration Fundamentals Command Reference for Cisco  
IOS Release 12.1.  
This chapter consists of these sections:  
•
•
•
Understanding CDP, page 17-1  
Configuring CDP, page 17-2  
Monitoring and Maintaining CDP, page 17-5  
Understanding CDP  
CDP is a device discovery protocol that runs over Layer 2 (the data link layer) on all Cisco-manufactured  
devices (routers, bridges, access servers, and switches) and allows network management applications to  
discover Cisco devices that are neighbors of already known devices. With CDP, network management  
applications can learn the device type and the Simple Network Management Protocol (SNMP) agent  
address of neighboring devices running lower-layer, transparent protocols. This feature enables  
applications to send SNMP queries to neighboring devices.  
CDP runs on all media that support Subnetwork Access Protocol (SNAP). Because CDP runs over the  
data-link layer only, two systems that support different network-layer protocols can learn about each  
other.  
Each CDP-configured device sends periodic messages to a multicast address, advertising at least one  
address at which it can receive SNMP messages. The advertisements also contain time-to-live, or  
holdtime information, which is the length of time a receiving device holds CDP information before  
discarding it. Each device also listens to the messages sent by other devices to learn about neighboring  
devices.  
The switch supports CDP Version 2.  
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Chapter 17 Configuring CDP  
Configuring CDP  
Configuring CDP  
These sections include CDP configuration information and procedures:  
•
•
•
•
Default CDP Configuration, page 17-2  
Configuring the CDP Characteristics, page 17-2  
Disabling and Enabling CDP, page 17-3  
Disabling and Enabling CDP on an Interface, page 17-4  
Default CDP Configuration  
Table 17-1 shows the default CDP configuration.  
Table 17-1  
Default CDP Configuration  
Feature  
Default Setting  
Enabled  
CDP global state  
CDP interface state  
Enabled  
CDP timer (packet update frequency)  
CDP holdtime (before discarding)  
CDP Version-2 advertisements  
60 seconds  
180 seconds  
Enabled  
Configuring the CDP Characteristics  
You can configure the frequency of CDP updates, the amount of time to hold the information before  
discarding it, and whether or not to send Version-2 advertisements.  
Beginning in privileged EXEC mode, follow these steps to configure the CDP timer, holdtime, and  
advertisement type.  
Note  
Steps 2 through 4 are all optional and can be performed in any order.  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
cdp timer seconds  
(Optional) Set the transmission frequency of CDP updates in seconds.  
The range is 5 to 254; the default is 60 seconds.  
Step 3  
cdp holdtime seconds  
(Optional) Specify the amount of time a receiving device should hold the  
information sent by your device before discarding it.  
The range is 10 to 255 seconds; the default is 180 seconds.  
(Optional) Configure CDP to send Version-2 advertisements.  
This is the default state.  
Step 4  
Step 5  
cdp advertise-v2  
end  
Return to privileged EXEC mode.  
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Chapter 17 Configuring CDP  
Configuring CDP  
Command  
Purpose  
Step 6  
Step 7  
show cdp  
Verify your settings.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Use the no form of the CDP commands to return to the default settings.  
This example shows how to configure CDP characteristics.  
Switch# configure terminal  
Switch(config)# cdp timer 50  
Switch(config)# cdp holdtime 120  
Switch(config)# cdp advertise-v2  
Switch(config)# end  
For additional CDP show commands, see the “Monitoring and Maintaining CDP” section on page 17-5.  
Disabling and Enabling CDP  
CDP is enabled by default.  
Beginning in privileged EXEC mode, follow these steps to disable the CDP device discovery capability:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
no cdp run  
end  
Enter global configuration mode.  
Disable CDP.  
Return to privileged EXEC mode.  
Beginning in privileged EXEC mode, follow these steps to enable CDP when it has been disabled:  
Command  
configure terminal  
cdp run  
Purpose  
Step 1  
Step 2  
Step 3  
Enter global configuration mode.  
Enable CDP after disabling it.  
Return to privileged EXEC mode.  
end  
This example shows how to enable CDP if it has been disabled.  
Switch# configure terminal  
Switch(config)# cdp run  
Switch(config)# end  
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Chapter 17 Configuring CDP  
Configuring CDP  
Disabling and Enabling CDP on an Interface  
CDP is enabled by default on all supported interfaces to send and receive CDP information.  
Beginning in privileged EXEC mode, follow these steps to disable CDP on an interface:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface on which you are disabling CDP, and enter  
interface configuration mode.  
Step 3  
Step 4  
Step 5  
no cdp enable  
Disable CDP on the interface.  
end  
Return to privileged EXEC mode.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Beginning in privileged EXEC mode, follow these steps to enable CDP on an interface when it has been  
disabled:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface on which you are enabling CDP, and enter  
interface configuration mode.  
Step 3  
Step 4  
Step 5  
cdp enable  
Enable CDP on the interface after disabling it.  
Return to privileged EXEC mode.  
end  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
This example shows how to enable CDP on an interface when it has been disabled.  
Switch# configure terminal  
Switch(config)# interface fastethernet0/1  
Switch(config-if)# cdp enable  
Switch(config-if)# end  
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Chapter 17 Configuring CDP  
Monitoring and Maintaining CDP  
Monitoring and Maintaining CDP  
To monitor and maintain CDP on your device, perform one or more of these tasks, beginning in  
privileged EXEC mode.  
Command  
Description  
clear cdp counters  
clear cdp table  
show cdp  
Reset the traffic counters to zero.  
Delete the CDP table of information about neighbors.  
Display global information, such as frequency of transmissions and the holdtime  
for packets being sent.  
show cdp entry entry-name  
[protocol | version]  
Display information about a specific neighbor.  
You can enter an asterisk (*) to display all CDP neighbors, or you can enter the  
name of the neighbor about which you want information.  
You can also limit the display to information about the protocols enabled on the  
specified neighbor or information about the version of software running on the  
device.  
show cdp interface [interface-id]  
Display information about interfaces where CDP is enabled.  
You can limit the display to the interface about which you want information.  
show cdp neighbors [interface-id]  
[detail]  
Display information about neighbors, including device type, interface type and  
number, holdtime settings, capabilities, platform, and port ID.  
You can limit the display to neighbors on a specific type or number of interface  
or expand the display to provide more detailed information.  
show cdp traffic  
Display CDP counters, including the number of packets sent and received and  
checksum errors.  
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Chapter 17 Configuring CDP  
Monitoring and Maintaining CDP  
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18  
Configuring SPAN and RSPAN  
This chapter describes how to configure Switched Port Analyzer (SPAN) and Remote SPAN (RSPAN)  
on your Cisco Systems Intelligent Gigabit Ethernet Switch Module.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
This chapter consists of these sections:  
•
•
•
•
Understanding SPAN and RSPAN, page 18-1  
Configuring SPAN, page 18-7  
Configuring RSPAN, page 18-12  
Displaying SPAN and RSPAN Status, page 18-17  
Understanding SPAN and RSPAN  
You can analyze network traffic passing through ports by using SPAN to send a copy of the traffic to  
another port on the switch that has been connected to a SwitchProbe device or other Remote Monitoring  
(RMON) probe or security device. SPAN mirrors received or sent (or both) traffic on one or more source  
ports to a destination port for analysis.  
For example, in Figure 18-1, all traffic on port 5 (the source port) is mirrored to port 17 (the destination  
port). A network analyzer on port 17 receives all network traffic from port 5 without being physically  
attached to port 5.  
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Chapter 18 Configuring SPAN and RSPAN  
Understanding SPAN and RSPAN  
Figure 18-1  
Example SPAN Configuration  
Port 5 traffic mirrored  
on Port 17  
1
2
3
4
5
6
7
8
9 10 11 12 13 14 17 18 19 20  
11 12  
10  
9
13  
18 19  
17  
8
14  
7
20  
6
5
4
3
2
1
Network analyzer  
Only traffic that enters or leaves source ports can be monitored by using SPAN.  
RSPAN extends SPAN by enabling remote monitoring of multiple switches across your network. The  
traffic for each RSPAN session is carried over a user-specified RSPAN VLAN that is dedicated for that  
RSPAN session in all participating switches. The SPAN traffic from the sources is copied onto the  
RSPAN VLAN through a reflector port and then forwarded over trunk ports that are carrying the RSPAN  
VLAN to any RSPAN destination sessions monitoring the RSPAN VLAN, as shown in Figure 18-2.  
Figure 18-2  
Example of RSPAN Configuration  
Source switch  
Intermediate switch  
Destination switch  
RSPAN  
VLAN  
RSPAN  
VLAN  
RSPAN  
source port  
Reflector  
port  
RSPAN  
destination port  
SPAN and RSPAN do not affect the switching of network traffic on source ports; a copy of the packets  
received or sent by the source interfaces are sent to the destination interface. Except for traffic that is  
required for the SPAN or RSPAN session, reflector ports and destination ports do not receive or forward  
traffic.  
You can use the SPAN destination port to inject traffic from a network security device. For example, if  
you connect a Cisco Intrusion Detection System (IDS) Sensor Appliance to a destination port, the IDS  
device can send TCP Reset packets to close down the TCP session of a suspected attacker.  
Note  
You cannot use the RSPAN destination port to inject traffic from a network security device. The switch  
does not support ingress forwarding on an RSPAN destination port.  
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Chapter 18 Configuring SPAN and RSPAN  
Understanding SPAN and RSPAN  
SPAN and RSPAN Concepts and Terminology  
This section describes concepts and terminology associated with SPAN and RSPAN configuration.  
SPAN Session  
A local SPAN session is an association of a destination port with source ports. You can monitor  
incoming or outgoing traffic on a series or range of ports.  
An RSPAN session is an association of source ports across your network with an RSPAN VLAN. The  
destination source is the RSPAN VLAN.  
SPAN sessions do not interfere with the normal operation of the switch. However, an oversubscribed  
SPAN destination, for example, a 10-Mbps port monitoring a 100-Mbps port, results in dropped or lost  
packets.  
You can configure SPAN sessions on disabled ports; however, a SPAN session does not become active  
unless you enable the destination port and at least one source port for that session. The show monitor  
session session_number privileged EXEC command displays the operational status of a SPAN session.  
A SPAN session remains inactive after system power-on until the destination port is operational.  
Traffic Types  
SPAN sessions include these traffic types:  
•
Receive (Rx) SPAN—The goal of receive (or ingress) SPAN is to monitor as much as possible all  
the packets received by the source interface. A copy of each packet received by the source is sent to  
the destination port for that SPAN session. You can monitor a series or range of ingress ports in a  
SPAN session.  
At the destination port, if tagging is enabled, the packets appear with the IEEE 802.1Q header. If no  
tagging is specified, packets appear in the native format.  
Packets that are modified because of quality of service (QoS)—for example, modified Differentiated  
Services Code Point (DSCP)—are copied with modification for Rx SPAN.  
•
Transmit (Tx) SPAN—The goal of transmit (or egress) SPAN is to monitor as much as possible all  
the packets sent by the source interface after all modification and processing is performed by the  
switch. A copy of each packet sent by the source is sent to the destination port for that SPAN session.  
The copy is provided after the packet is modified. You can monitor a range of egress ports in a  
SPAN session.  
For packets that are modified because of QoS, the modified packet might not have the same DSCP  
(IP packet) or CoS (non-IP packet) as the SPAN source.  
Some features that can cause a packet to be dropped during transmit processing might also affect  
the duplicated copy for SPAN.These features include IP standard and extended output ACLs on  
multicast packets, and egress QoS policing. In the case of output ACLs, if the SPAN source drops  
the packet, the SPAN destination would also drop the packet. If the source port is oversubscribed,  
the destination ports will have different dropping behavior.  
•
Both—In a SPAN session, you can monitor a series or range of ports for both received and sent  
packets.  
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Chapter 18 Configuring SPAN and RSPAN  
Understanding SPAN and RSPAN  
Source Port  
A source port (also called a monitored port) is a switched port that you monitor for network traffic  
analysis. In a single local SPAN session or RSPAN source session, you can monitor source port traffic  
such as received (Rx), transmitted (Tx), or bidirectional (both). The switch supports any number of  
source ports (up to the maximum number of available ports on the switch).  
A source port has these characteristics:  
•
•
•
It can be any port type (for example, EtherChannel, Fast Ethernet, Gigabit Ethernet, and so forth).  
It cannot be a destination port.  
Each source port can be configured with a direction (ingress, egress, or both) to monitor. For  
EtherChannel sources, the monitored direction would apply to all the physical ports in the group.  
•
Source ports can be in the same or different VLANs.  
You can configure a trunk port as a source port. All VLANs active on the trunk are monitored.  
Destination Port  
Each local SPAN session or RSPAN destination session must have a destination port (also called a  
monitoring port) that receives a copy of traffic from the source port.  
The destination port has these characteristics:  
•
•
•
•
•
It must reside on the same switch as the source port (for a local SPAN session).  
It can be any Ethernet physical port.  
It cannot be a source port or a reflector port.  
It cannot be an EtherChannel group or a VLAN.  
It can be a physical port that is assigned to an EtherChannel group, even if the EtherChannel group  
has been specified as a SPAN source. The port is removed from the group while it is configured as  
a SPAN destination port.  
•
•
The port does not transmit any traffic except that required for the SPAN session.  
If ingress traffic forwarding is enabled for a network security device, the destination port forwards  
traffic at Layer 2.  
•
•
It does not participate in spanning tree while the SPAN session is active.  
When it is a destination port, it does not participate in any of the Layer 2 protocols— Cisco  
Discovery Protocol (CDP), VLAN Trunk Protocol (VTP), Dynamic Trunking Protocol (DTP),  
Spanning Tree Protocol (STP), Port Aggregation Protocol (PagP), and Link Aggregation Control  
Protocol (LACP).  
•
•
No address learning occurs on the destination port.  
A destination port receives copies of sent and received traffic for all monitored source ports. If a  
destination port is oversubscribed, it could become congested. This could affect traffic forwarding  
on one or more of the source ports.  
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Chapter 18 Configuring SPAN and RSPAN  
Understanding SPAN and RSPAN  
Reflector Port  
The reflector port is the mechanism that copies packets onto an RSPAN VLAN. The reflector port  
forwards only the traffic from the RSPAN source session with which it is affiliated. Any device  
connected to a port set as a reflector port loses connectivity until the RSPAN source session is disabled.  
The reflector port has these characteristics:  
•
•
•
It is a port set to loopback.  
It cannot be an EtherChannel group, it does not trunk, and it cannot do protocol filtering.  
It can be a physical port that is assigned to an EtherChannel group, even if the EtherChannel group  
is specified as a SPAN source. The port is removed from the group while it is configured as a  
reflector port.  
•
A port used as a reflector port cannot be a SPAN source or destination port, nor can a port be a  
reflector port for more than one session at a time.  
•
•
•
It is invisible to all VLANs.  
The native VLAN for looped-back traffic on a reflector port is the RSPAN VLAN.  
The reflector port loops back untagged traffic to the switch. The traffic is then placed on the RSPAN  
VLAN and flooded to any trunk ports that carry the RSPAN VLAN.  
•
•
Spanning tree is automatically disabled on a reflector port.  
A reflector port receives copies of sent and received traffic for all monitored source ports. If a  
reflector port is oversubscribed, it could become congested. This could affect traffic forwarding on  
one or more of the source ports.  
If the bandwidth of the reflector port is not sufficient for the traffic volume from the corresponding  
source ports, the excess packets are dropped. A Gigabit port reflects at 1 Gbps.  
SPAN Traffic  
You can use local SPAN to monitor all network traffic, including multicast and bridge protocol data unit  
(BPDU) packets, and CDP, VTP, DTP, STP, PagP, and LACP packets. You cannot use RSPAN to  
monitor Layer 2 protocols. See the “RSPAN Configuration Guidelines” section on page 18-12 for more  
information.  
In some SPAN configurations, multiple copies of the same source packet are sent to the SPAN  
destination port. For example, a bidirectional (both Rx and Tx) SPAN session is configured for the  
sources a1 Rx monitor and the a2 Rx and Tx monitor to destination port d1. If a packet enters the switch  
through a1 and is switched to a2, both incoming and outgoing packets are sent to destination port d1.  
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Chapter 18 Configuring SPAN and RSPAN  
Understanding SPAN and RSPAN  
SPAN and RSPAN Interaction with Other Features  
SPAN interacts with these features:  
•
Spanning Tree Protocol (STP)—A destination port or a reflector port does not participate in STP  
while its SPAN or RSPAN session is active. The destination or reflector port can participate in STP  
after the SPAN or RSPAN session is disabled. On a source port, SPAN does not affect the STP  
status. STP can be active on trunk ports carrying an RSPAN VLAN.  
•
Cisco Discovery Protocol (CDP)—A SPAN destination port does not participate in CDP while the  
SPAN session is active. After the SPAN session is disabled, the port again participates in CDP.  
•
•
VLAN Trunking Protocol (VTP)—You can use VTP to prune an RSPAN VLAN between switches.  
VLAN and trunking—You can modify VLAN membership or trunk settings for source, destination,  
or reflector ports at any time. However, changes in VLAN membership or trunk settings for a  
destination or reflector port do not take effect until you disable the SPAN or RSPAN session.  
Changes in VLAN membership or trunk settings for a source port immediately take effect, and the  
SPAN session automatically adjusts accordingly.  
•
EtherChannel—You can configure an EtherChannel group as a source port but not as a SPAN  
destination port. When a group is configured as a SPAN source, the entire group is monitored.  
If a port is added to a monitored EtherChannel group, the new port is added to the SPAN source port  
list. If a port is removed from a monitored EtherChannel group, it is automatically removed from  
the source port list. If the port is the only port in the EtherChannel group, the EtherChannel group  
is removed from SPAN.  
If a physical port that belongs to an EtherChannel group is configured as a SPAN source,  
destination, or reflector port, it is removed from the group. After the port is removed from the SPAN  
session, it rejoins the EtherChannel group. Ports removed from an EtherChannel group remain  
members of the group, but they are in the down or standalone state.  
If a physical port that belongs to an EtherChannel group is a destination or reflector port and the  
EtherChannel group is a source, the port is removed from the EtherChannel group and from the list  
of monitored ports.  
•
QoS—For ingress monitoring, the packets sent to the SPAN destination port might be different from  
the packets actually received at the SPAN source port because the packets are forwarded after  
ingress QoS classification and policing. The packet DSCP might not be the same as the received  
packet.  
•
•
Multicast traffic can be monitored. For egress and ingress port monitoring, only a single unedited  
packet is sent to the SPAN destination port. It does not reflect the number of times the multicast  
packet is sent.  
Port security—A secure port cannot be a SPAN destination port.  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring SPAN  
SPAN and RSPAN Session Limits  
You can configure (and store in NVRAM) one local SPAN session or multiple RSPAN sessions on a  
switch. The number of active sessions and combinations are subject to these restrictions:  
•
•
•
•
SPAN or RSPAN source (rx, tx, both): 1 active session limit. (SPAN and RSPAN are mutually  
exclusive on a source switch).  
RSPAN source sessions have one destination per session with an RSPAN VLAN associated for that  
session.  
Each RSPAN destination session has one or more destination interfaces for each RSPAN VLAN that  
they support.  
RSPAN destination sessions are limited to two, or one if a local SPAN or a source RSPAN session  
is configured on the same switch.  
Default SPAN and RSPAN Configuration  
Table 18-1 shows the default SPAN and RSPAN configuration.  
Table 18-1  
Default SPAN and RSPAN Configuration  
Feature  
Default Setting  
SPAN state  
Disabled.  
Source port traffic to monitor  
Both received and sent traffic (both).  
Native form (no encapsulation type header).  
Disabled.  
Encapsulation type (destination port)  
Ingress forwarding (destination port)  
Configuring SPAN  
This section describes how to configure SPAN on your switch. It contains this configuration  
information:  
•
•
•
•
SPAN Configuration Guidelines, page 18-7  
Creating a SPAN Session and Specifying Ports to Monitor, page 18-8  
Creating a SPAN Session and Enabling Ingress Traffic, page 18-9  
Removing Ports from a SPAN Session, page 18-11  
SPAN Configuration Guidelines  
Follow these guidelines when configuring SPAN:  
•
SPAN sessions can coexist with RSPAN sessions within the limits described in the “SPAN and  
RSPAN Session Limits” section on page 18-7.  
•
•
The destination port cannot be a source port; a source port cannot be a destination port.  
You can have only one destination port per SPAN session. You cannot have two SPAN sessions  
using the same destination port.  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring SPAN  
•
•
An EtherChannel port can be a SPAN source port; it cannot be a SPAN destination port.  
For SPAN source ports, you can monitor sent and received traffic for a single port or for a series or  
range of ports.  
•
•
•
When you configure a switch port as a SPAN destination port, it is no longer a normal switch port;  
only monitored traffic passes through the SPAN destination port.  
You can configure a disabled port to be a source or destination port, but the SPAN function does not  
start until the destination port and at least one source port is enabled.  
A SPAN destination port never participates in any VLAN spanning tree. SPAN does include BPDUs  
in the monitored traffic, so any spanning-tree BPDUs received on the SPAN destination port for a  
SPAN session were copied from the SPAN source ports.  
•
When SPAN is enabled, configuration changes have these results:  
–
If you change the VLAN configuration of a destination port, the change is not effective until  
SPAN is disabled.  
–
If you disable all source ports or the destination port, the SPAN function stops until both a  
source and the destination port are enabled.  
Creating a SPAN Session and Specifying Ports to Monitor  
Beginning in privileged EXEC mode, follow these steps to create a SPAN session and specify the source  
(monitored) and destination (monitoring) ports:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
no monitor session {session_number | all | Clear any existing SPAN configuration for the session.  
local | remote}  
For session_number, specify 1.  
Specify all to remove all SPAN sessions, local to remove all local  
sessions, or remote to remove all remote SPAN sessions.  
Step 3  
monitor session session_number source  
interface interface-id [, | -] [both | rx | tx]  
Specify the SPAN session and the source port (monitored port).  
For session_number, specify 1.  
For interface-id, specify the source port to monitor. Valid interfaces  
include physical interfaces and port-channel logical interfaces  
(port-channel port-channel-number).  
(Optional) [, | -] Specify a series or range of interfaces. Enter a space  
before and after the comma; enter a space before and after the  
hyphen.  
(Optional) Specify the direction of traffic to monitor. If you do not  
specify a traffic direction, the source interface sends both sent and  
received traffic.  
•
•
•
both—Monitor both received and sent traffic.  
rx—Monitor received traffic.  
tx—Monitor sent traffic.  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring SPAN  
Command  
Purpose  
Step 4  
monitor session session_number  
destination interface interface-id  
[encapsulation {dot1q}]  
Specify the SPAN session and the destination port (monitoring port).  
For session_number, specify 1.  
For interface-id, specify the destination port. Valid interfaces include  
physical interfaces.  
(Optional) Specify the encapsulation header for outgoing packets. If  
not specified, packets are sent in native form.  
•
dot1q—Use IEEE 802.1Q encapsulation.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show monitor [session session_number]  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
This example shows how to set up a SPAN session, session 1, for monitoring source port traffic to a  
destination port. First, any existing SPAN configuration for session 1 is cleared, and then bidirectional  
traffic is mirrored from source port 17 to destination port 18.  
Switch(config)# no monitor session 1  
Switch(config)# monitor session 1 source interface gigabitethernet0/17  
Switch(config)# monitor session 1 destination interface gigabitethernet0/18  
encapsulation dot1q  
Switch(config)# end  
Creating a SPAN Session and Enabling Ingress Traffic  
Beginning in privileged EXEC mode, follow these steps to create a SPAN session, to specify the source  
and destination ports, and to enable ingress traffic on the destination port for a network security device  
(such as a Cisco IDS Sensor Appliance):  
Command  
configure terminal  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
no monitor session {session_number | all | Clear any existing SPAN configuration for the session.  
local | remote}  
For session_number, specify 1.  
Specify all to remove all SPAN sessions, local to remove all local  
sessions, or remote to remove all remote SPAN sessions.  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring SPAN  
Command  
Purpose  
Step 3  
monitor session session_number source  
Specify the SPAN session and the source port (monitored port).  
interface interface-id [, | -] [both | rx | tx]  
For session_number, specify 1.  
For interface-id, specify the source port to monitor. Valid interfaces  
include physical interfaces and port-channel logical interfaces  
(port-channel port-channel-number).  
(Optional) [, | -] Specify a series or range of interfaces. Enter a space  
before and after the comma; enter a space before and after the  
hyphen.  
(Optional) Specify the direction of traffic to monitor. If you do not  
specify a traffic direction, the source interface sends both sent and  
received traffic.  
•
•
•
both—Monitor both received and sent traffic.  
rx—Monitor received traffic.  
tx—Monitor sent traffic.  
Step 4  
monitor session session_number  
destination interface interface-id  
[encapsulation {dot1q}] [ingress vlan  
vlan id]  
Specify the SPAN session, the destination port (monitoring port), the  
packet encapsulation, and the ingress VLAN.  
For session_number, specify 1.  
For interface-id, specify the destination port. Valid interfaces include  
physical interfaces.  
(Optional) Specify the encapsulation header for outgoing packets. If  
not specified, packets are sent in native form.  
•
dot1q—Use IEEE 802.1Q encapsulation.  
(Optional) Enter ingress vlan vlan id to enable ingress forwarding  
and specify a default VLAN.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show monitor [session session_number]  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
This example shows how to configure the destination port for ingress traffic on VLAN 5 by using a  
security device that does not support IEEE 802.1Q encapsulation.  
Switch(config)# monitor session 1 destination interface gigabitethernet0/17 ingress vlan 5  
This example shows how to configure the destination port for ingress traffic on VLAN 5 by using a  
security device that supports IEEE 802.1Q encapsulation.  
Switch(config)# monitor session 1 destination interface gigabitethernet0/17 encapsulation  
dot1q ingress vlan 5  
This example shows how to disable ingress traffic forwarding on the destination port.  
Switch(config)# monitor session 1 destination interface gigabitethernet0/17 encapsulation  
dot1q  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring SPAN  
Removing Ports from a SPAN Session  
Beginning in privileged EXEC mode, follow these steps to remove a port as a SPAN source for a session:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
no monitor session session_number source  
interface interface-id [, | -] [both | rx | tx]  
Specify the characteristics of the source port (monitored port) and  
SPAN session to remove.  
For session, specify 1.  
For interface-id, specify the source port to no longer monitor. Valid  
interfaces include physical interfaces and port-channel logical  
interfaces (port-channel port-channel-number).  
(Optional) Use [, | -] to specify a series or range of interfaces if they  
were configured. This option is valid when monitoring only  
received traffic. Enter a space before and after the comma; enter a  
space before and after the hyphen.  
(Optional) Specify the direction of traffic (both, rx, or tx) to no  
longer monitor. If you do not specify a traffic direction, both  
transmit and receive are disabled.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show monitor [session session_number]  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To remove a source or destination port from the SPAN session, use the no monitor session  
session_number source interface interface-id global configuration command or the no monitor session  
session_number destination interface interface-id global configuration command. To change the  
encapsulation type back to the default (native), use the monitor session session_number destination  
interface interface-id without the encapsulation keyword.  
This example shows how to remove a port as a SPAN source for SPAN session 1:  
Switch(config)# no monitor session 1 source interface gigabitethernet0/17  
Switch(config)# end  
This example shows how to disable received traffic monitoring on a port that was configured for  
bidirectional monitoring:  
Switch(config)# no monitor session 1 source interface gigabitethernet0/17 rx  
The monitoring of traffic received on port 1 is disabled, but traffic sent from this port continues to be  
monitored.  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring RSPAN  
Configuring RSPAN  
This section describes how to configure RSPAN on your switch. It contains this configuration  
information:  
•
•
•
•
•
RSPAN Configuration Guidelines, page 18-12  
Configuring a VLAN as an RSPAN VLAN, page 18-13  
Creating an RSPAN Source Session, page 18-14  
Creating an RSPAN Destination Session, page 18-15  
Removing Ports from an RSPAN Session, page 18-16  
RSPAN Configuration Guidelines  
To use the RSPAN feature described in this section, you must have the EI installed on your switch.  
Follow these guidelines when configuring RSPAN:  
•
•
All the items in the “SPAN Configuration Guidelines” section on page 18-7 apply to RSPAN.  
As RSPAN VLANs have special properties, you should reserve a few VLANs across your network  
for use as RSPAN VLANs; do not assign access ports to these VLANs.  
•
•
•
•
RSPAN sessions can coexist with SPAN sessions within the limits described in the “SPAN and  
RSPAN Session Limits” section on page 18-7.  
For RSPAN configuration, you can distribute the source ports and the destination ports across  
multiple switches in your network.  
A port cannot serve as an RSPAN source port or RSPAN destination port while designated as an  
RSPAN reflector port.  
When you configure a switch port as a reflector port, it is no longer a normal switch port; only  
looped-back traffic passes through the reflector port.  
•
•
RSPAN does not support BPDU packet monitoring or other Layer 2 switch protocols.  
You can configure any VLAN as an RSPAN VLAN as long as these conditions are met:  
–
–
–
–
The RSPAN VLAN is not configured as a native VLAN.  
Extended range RSPAN VLANs will not be propagated to other switches using VTP.  
No access port is configured in the RSPAN VLAN.  
All participating switches support RSPAN.  
Note  
The RSPAN VLAN cannot be VLAN 1 (the default VLAN) or VLAN IDs 1002 through  
1005 (reserved to Token Ring and FDDI VLANs).  
•
•
You should create an RSPAN VLAN before configuring an RSPAN source or destination session.  
If you enable VTP and VTP pruning, RSPAN traffic is pruned in the trunks to prevent the unwanted  
flooding of RSPAN traffic across the network for VLAN-IDs that are lower than 1005.  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring RSPAN  
Configuring a VLAN as an RSPAN VLAN  
First create a new VLAN to be the RSPAN VLAN for the RSPAN session. You must create the RSPAN  
VLAN in all switches that will participate in RSPAN. If the RSPAN VLAN-ID is in the normal range  
(lower than 1005) and VTP is enabled in the network, you can create the RSPAN VLAN in one switch,  
and VTP propagates it to the other switches in the VTP domain. For extended-range VLANs (greater  
than 1005), you must configure RSPAN VLAN on both source and destination switches and any  
intermediate switches.  
Use VTP pruning to get an efficient flow of RSPAN traffic, or manually delete the RSPAN VLAN from  
all trunks that do not need to carry the RSPAN traffic.  
Beginning in privileged EXEC mode, follow these steps to create an RSPAN VLAN:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
vlan vlan-id  
Enter a VLAN ID to create a VLAN, or enter the VLAN ID of an  
existing VLAN, and enter VLAN configuration mode. The range is  
2 to 1001 and 1006 to 4094.  
Note  
The RSPAN VLAN cannot be VLAN 1 (the default VLAN)  
or VLAN IDs 1002 through 1005 (reserved for Token Ring  
and FDDI VLANs).  
Step 3  
Step 4  
Step 5  
remote-span  
Configure the VLAN as an RSPAN VLAN.  
Return to privileged EXEC mode.  
end  
copy running-config startup-config  
(Optional) Save the configuration in the configuration file.  
To remove the remote SPAN characteristic from a VLAN and convert it back to a normal VLAN, use  
the no remote-span VLAN configuration command.  
This example shows how to create RSPAN VLAN 901.  
Switch(config)# vlan 901  
Switch(config-vlan)# remote span  
Switch(config-vlan)# end  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring RSPAN  
Creating an RSPAN Source Session  
Beginning in privileged EXEC mode, follow these steps to start an RSPAN source session and to specify  
the monitored source and the destination RSPAN VLAN:  
Command  
configure terminal  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
no monitor session {session_number | all | Clear any existing RSPAN configuration for the session.  
local | remote}  
For session_number, specify the session number identified with this  
RSPAN session.  
Specify all to remove all RSPAN sessions, local to remove all local  
sessions, or remote to remove all remote SPAN sessions.  
Step 3  
monitor session session_number source  
interface interface-id [, | -] [both | rx | tx]  
Specify the RSPAN session and the source port (monitored port).  
For session_number, specify the session number identified with this  
RSPAN session.  
For interface-id, specify the source port to monitor. Valid interfaces  
include physical interfaces and port-channel logical interfaces  
(port-channel port-channel-number).  
(Optional) [, | -] Specify a series or range of interfaces. Enter a space  
before and after the comma; enter a space before and after the  
hyphen.  
(Optional) Specify the direction of traffic to monitor. If you do not  
specify a traffic direction, the source interface sends both sent and  
received traffic.  
•
•
•
both—Monitor both received and sent traffic.  
rx—Monitor received traffic.  
tx—Monitor sent traffic.  
Step 4  
monitor session session_number  
destination remote vlan vlan-id  
reflector-port interface  
Specify the RSPAN session, the destination remote VLAN, and the  
reflector port.  
For session_number, enter the session number identified with this  
RSPAN session.  
For vlan-id, specify the RSPAN VLAN to carry the monitored traffic  
to the destination port. (See the “Creating or Modifying an Ethernet  
VLAN” section on page 12-8 for more information about creating an  
RSPAN VLAN.)  
For interface, specify the interface that will flood the RSPAN traffic  
onto the RSPAN VLAN.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show monitor [session session_number]  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring RSPAN  
This example shows how to clear any existing RSPAN configuration for session 1, configure RSPAN  
session 1 to monitor multiple source interfaces, and configure the destination RSPAN VLAN and the  
reflector-port.  
Switch(config)# no monitor session 1  
Switch(config)# monitor session 1 source interface gigabitethernet0/17 tx  
Switch(config)# monitor session 1 source interface gigabitethernet0/18 rx  
Switch(config)# monitor session 1 source interface gigabitethernet0/19 rx  
Switch(config)# monitor session 1 source interface port-channel 102 rx  
Switch(config)# monitor session 1 destination remote vlan 901 reflector-port  
gigabitethernet0/14  
Switch(config)# end  
Creating an RSPAN Destination Session  
Beginning in privileged EXEC mode, follow these steps to create an RSPAN destination session and to  
specify the source RSPAN VLAN and the destination port:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
monitor session session_number source  
remote vlan vlan-id  
Specify the RSPAN session and the source RSPAN VLAN.  
For session_number, specify the session number identified with this  
RSPAN session.  
For vlan-id, specify the source RSPAN VLAN to monitor.  
Specify the RSPAN session and the destination interface.  
For session_number, specify.  
Step 3  
monitor session session_number  
destination interface interface-id  
[encapsulation {dot1q}]  
For interface-id, specify the destination interface.  
(Optional) Specify the encapsulation header for outgoing packets. If  
not specified, packets are sent in native form.  
•
dot1q—Use IEEE 802.1Q encapsulation.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show monitor [session session_number]  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
This example shows how to configure VLAN 901 as the source remote VLAN and port 17 as the  
destination interface:  
Switch(config)# monitor session 1 source remote vlan 901  
Switch(config)# monitor session 1 destination interface gigabitethernet0/17  
Switch(config)# end  
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Chapter 18 Configuring SPAN and RSPAN  
Configuring RSPAN  
Removing Ports from an RSPAN Session  
Beginning in privileged EXEC mode, follow these steps to remove a port as an RSPAN source for a  
session:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
no monitor session session_number source  
interface interface-id [, | -] [both | rx | tx]  
Specify the characteristics of the RSPAN source port (monitored  
port) to remove.  
For session_number, specify the session number identified with  
this RSPAN session.  
For interface-id, specify the source port to no longer monitor. Valid  
interfaces include physical interfaces and port-channel logical  
interfaces (port-channel port-channel-number).  
(Optional) Use [, | -] to specify a series or range of interfaces if they  
were configured. Enter a space before and after the comma; enter  
a space before and after the hyphen.  
(Optional) Specify the direction of traffic (both, rx, or tx) to no  
longer monitor. If you do not specify a traffic direction, both  
transmit and receive are disabled.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show monitor [session session_number]  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
This example shows how to remove port 17 as an RSPAN source for RSPAN session 1:  
Switch(config)# no monitor session 1 source interface gigabitethernet0/17  
Switch(config)# end  
This example shows how to disable received traffic monitoring on port 17, which was configured for  
bidirectional monitoring:  
Switch(config)# no monitor session 1 source interface gigabitethernet0/17 rx  
The monitoring of traffic received on port 1 is disabled, but traffic sent from this port continues to be  
monitored.  
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Chapter 18 Configuring SPAN and RSPAN  
Displaying SPAN and RSPAN Status  
Displaying SPAN and RSPAN Status  
To display the status of the current SPAN or RSPAN configuration, use the show monitor privileged  
EXEC command.  
This is an example of output for the show monitor privileged EXEC command for SPAN source  
session 1:  
Switch# show monitor session 1  
Session 1  
---------  
Type  
: Local Session  
:
: None  
: None  
: Fa0/4  
:
: None  
: None  
: None  
Source Ports  
RX Only  
TX Only  
Both  
Source VLANs  
RX Only  
TX Only  
Both  
Source RSPAN VLAN : None  
Destination Ports : Fa0/5  
Encapsulation: DOT1Q  
Ingress: Enabled, default VLAN = 5  
Reflector Port : None  
Filter VLANs  
Dest RSPAN VLAN  
: None  
: None  
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Chapter 18 Configuring SPAN and RSPAN  
Displaying SPAN and RSPAN Status  
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C H A P T E R  
19  
Configuring RMON  
This chapter describes how to configure Remote Network Monitoring (RMON) on your Cisco Systems  
Intelligent Gigabit Ethernet Switch Module. RMON is a standard monitoring specification that defines  
a set of statistics and functions that can be exchanged between RMON-compliant console systems and  
network probes. RMON provides you with comprehensive network-fault diagnosis, planning, and  
performance-tuning information.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the Cisco IOS  
Configuration Fundamentals Command Reference for Cisco IOS Release 12.1.  
This chapter consists of these sections:  
•
•
•
Understanding RMON, page 19-1  
Configuring RMON, page 19-2  
Displaying RMON Status, page 19-6  
Understanding RMON  
RMON is an Internet Engineering Task Force (IETF) standard monitoring specification that allows  
various network agents and console systems to exchange network monitoring data. You can use the  
RMON feature with the Simple Network Management Protocol (SNMP) agent in the switch to monitor  
all the traffic flowing among switches on all connected LAN segments.  
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Chapter 19 Configuring RMON  
Configuring RMON  
Figure 19-1  
Remote Monitoring Example  
Network management station with  
generic RMON console application  
Catalyst 3550 switch  
RMON alarms and events  
configured. SNMP configured.  
RMON history  
and statistic  
collection enabled.  
BladeCenter  
BladeCenter  
The switch supports these RMON groups (defined in RFC 1757):  
•
•
•
Statistics (RMON group 1)—Collects Ethernet, Fast Ethernet, and Gigabit Ethernet statistics on an  
interface.  
History (RMON group 2)—Collects a history group of statistics on Ethernet, Fast Ethernet, and  
Gigabit Ethernet interfaces for a specified polling interval.  
Alarm (RMON group 3)—Monitors a specific MIB object for a specified interval, triggers an alarm  
at a specified value (rising threshold), and resets the alarm at another value (falling threshold).  
Alarms can be used with events; the alarm triggers an event, which can generate a log entry or an  
SNMP trap.  
•
Event (RMON group 9)—Determines the action to take when an event is triggered by an alarm. The  
action can be to generate a log entry or an SNMP trap.  
Because switches supported by this software release use hardware counters for RMON data processing,  
the monitoring is more efficient, and little processing power is required.  
Configuring RMON  
This section describes how to configure RMON on your switch. It contains this configuration  
information:  
•
•
•
Default RMON Configuration, page 19-3  
Configuring RMON Alarms and Events, page 19-3  
Configuring RMON Collection on an Interface, page 19-5  
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Chapter 19 Configuring RMON  
Configuring RMON  
Default RMON Configuration  
RMON is disabled by default; no alarms or events are configured.  
Only RMON 1 is supported on the switch.  
Configuring RMON Alarms and Events  
You can configure your switch for RMON by using the command-line interface (CLI) or an  
SNMP-compatible network management station. We recommend that you use a generic RMON console  
application on the network management station (NMS) to take advantage of RMON’s network  
management capabilities. You must also configure SNMP on the switch to access RMON MIB objects.  
For more information, see Chapter 21, “Configuring SNMP.”  
Beginning in privileged EXEC mode, follow these steps to enable RMON alarms and events:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Set an alarm on a MIB object.  
rmon alarm number variable interval {absolute | delta}  
rising-threshold value [event-number]  
falling-threshold value [event-number]  
[owner string]  
•
For number, specify the alarm number. The  
range is 1 to 65535.  
•
•
For variable, specify the MIB object to monitor.  
For interval, specify the time in seconds the  
alarm monitors the MIB variable. The range is  
1 to 4294967295 seconds.  
•
•
Specify the absolute keyword to test each MIB  
variable directly; specify the delta keyword to  
test the change between samples of a MIB  
variable.  
For value, specify a number at which the alarm  
is triggered and one for when the alarm is reset.  
The range for the rising threshold and falling  
threshold values is -2147483648 to  
2147483647.  
•
•
(Optional) For event-number, specify the event  
number to trigger when the rising or falling  
threshold exceeds its limit.  
(Optional) For owner string, specify the owner  
of the alarm.  
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Chapter 19 Configuring RMON  
Configuring RMON  
Command  
Purpose  
Step 3  
rmon event number [description string] [log] [owner string] Add an event in the RMON event table that is  
[trap community]  
associated with an RMON event number.  
•
•
•
•
•
For number, assign an event number. The range  
is 1 to 65535.  
(Optional) For description string, specify a  
description of the event.  
(Optional) Use the log keyword to generate an  
RMON log entry when the event is triggered.  
(Optional) For owner string, specify the owner  
of this event.  
(Optional) For community, enter the SNMP  
community string used for this trap.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration  
file.  
To disable an alarm, use the no rmon alarm number global configuration command on each alarm you  
configured. You cannot disable at once all the alarms that you configured. To disable an event, use the  
no rmon event number global configuration command. To learn more about alarms and events and how  
they interact with each other, see RFC 1757.  
You can set an alarm on any MIB object. The following example configures RMON alarm number 10  
by using the rmon alarm command. The alarm monitors the MIB variable ifEntry.20.1 once every 20  
seconds until the alarm is disabled and checks the change in the variable’s rise or fall. If the ifEntry.20.1  
value shows a MIB counter increase of 15 or more, such as from 100000 to 100015, the alarm is  
triggered. The alarm in turn triggers event number 1, which is configured with the rmon event  
command. Possible events can include a log entry or an SNMP trap. If the ifEntry.20.1 value changes  
by 0, the alarm is reset and can be triggered again.  
Switch(config)# rmon alarm 10 ifEntry.20.1 20 delta rising-threshold 15 1  
falling-threshold 0 owner jjohnson  
The following example creates RMON event number 1 by using the rmon event command. The event  
is defined as High ifOutErrors and generates a log entry when the event is triggered by the alarm. The  
user jjones owns the row that is created in the event table by this command. This example also generates  
an SNMP trap when the event is triggered.  
Switch(config)# rmon event 1 log trap eventtrap description “High ifOutErrors” owner  
jjones  
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Chapter 19 Configuring RMON  
Configuring RMON  
Configuring RMON Collection on an Interface  
You must first configure RMON alarms and events to display collection information.  
Beginning in privileged EXEC mode, follow these steps to collect group history statistics on an  
interface:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface on which to collect history, and enter  
interface configuration mode.  
Step 3  
rmon collection history index  
[buckets bucket-number] [interval seconds]  
[owner ownername]  
Enable history collection for the specified number of buckets and  
time period.  
•
For index, identify the RMON group of statistics The range  
is 1 to 65535.  
•
(Optional) For buckets bucket-number, specify the  
maximum number of buckets desired for the RMON  
collection history group of statistics. The range is 1 to  
65535. The default is 50 buckets.  
•
•
(Optional) For interval seconds, specify the number of  
seconds in each polling cycle.  
(Optional) For owner ownername, enter the name of the  
owner of the RMON group of statistics.  
Step 4  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
show running-config  
show rmon history  
copy running-config startup-config  
Verify your entries.  
Display the contents of the switch history table.  
(Optional) Save your entries in the configuration file.  
To disable history collection, use the no rmon collection history index interface configuration  
command.  
Beginning in privileged EXEC mode, follow these steps to collect group Ethernet statistics on an  
interface:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface on which to collect statistics, and enter  
interface configuration mode.  
Step 3  
rmon collection stats index [owner ownername] Enable RMON statistic collection on the interface.  
•
For index, specify the RMON group of statistics. The range  
is from 1 to 65535.  
•
(Optional) For owner ownername, enter the name of the  
owner of the RMON group of statistics.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
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Chapter 19 Configuring RMON  
Displaying RMON Status  
Command  
Purpose  
Step 6  
Step 7  
show rmon statistics  
Display the contents of the switch statistics table.  
(Optional) Save your entries in the configuration file.  
copy running-config startup-config  
To disable the collection of group Ethernet statistics, use the no rmon collection stats index interface  
configuration command.  
Displaying RMON Status  
To display the RMON status, use one or more of the privileged EXEC commands in Table 19-1:  
Table 19-1  
Commands for Displaying RMON Status  
Command  
Purpose  
show rmon  
Displays general RMON statistics.  
Displays the RMON alarm table.  
Displays the RMON event table.  
Displays the RMON history table.  
Displays the RMON statistics table.  
show rmon alarms  
show rmon events  
show rmon history  
show rmon statistics  
For information about the fields in these displays, see the Cisco IOS Configuration Fundamentals  
Command Reference for Cisco IOS Release 12.1.  
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C H A P T E R  
20  
Configuring System Message Logging  
This chapter describes how to configure system message logging on your Cisco Systems Intelligent  
Gigabit Ethernet Switch Module.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the Cisco IOS  
Configuration Fundamentals Command Reference, Release 12.1.  
This chapter consists of these sections:  
•
•
•
Understanding System Message Logging, page 20-1  
Configuring System Message Logging, page 20-2  
Displaying the Logging Configuration, page 20-12  
Understanding System Message Logging  
By default, a switch sends the output from system messages and debug privileged EXEC commands to  
a logging process. The logging process controls the distribution of logging messages to various  
destinations, such as the logging buffer, terminal lines, or a UNIX syslog server, depending on your  
configuration. The process also sends messages to the console.  
Note  
The syslog format is compatible with 4.3 BSD UNIX.  
When the logging process is disabled, messages are sent only to the console. The messages are sent as  
they are generated, so message and debug output are interspersed with prompts or output from other  
commands. Messages appear on the console after the process that generated them has finished.  
You can set the severity level of the messages to control the type of messages displayed on the console  
and each of the destinations. You can timestamp log messages or set the syslog source address to  
enhance real-time debugging and management. For information on possible messages, see the system  
message guide for this release.  
You can access logged system messages by using the switch command-line interface (CLI) or by saving  
them to a properly configured syslog server. The switch software saves syslog messages in an internal  
buffer. You can remotely monitor system messages by accessing the switch through Telnet, through the  
service port, or by viewing the logs on a syslog server.  
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Chapter 20 Configuring System Message Logging  
Configuring System Message Logging  
Configuring System Message Logging  
These sections describe how to configure system message logging:  
•
•
•
•
•
•
•
•
•
•
System Log Message Format, page 20-2  
Default System Message Logging Configuration, page 20-3  
Disabling and Enabling Message Logging, page 20-4  
Setting the Message Display Destination Device, page 20-4  
Synchronizing Log Messages, page 20-6  
Enabling and Disabling Timestamps on Log Messages, page 20-7  
Enabling and Disabling Sequence Numbers in Log Messages, page 20-8  
Defining the Message Severity Level, page 20-8  
Limiting Syslog Messages Sent to the History Table and to SNMP, page 20-10  
Configuring UNIX Syslog Servers, page 20-10  
System Log Message Format  
System log messages can contain up to 80 characters and a percent sign (%), which follows the optional  
sequence number or timestamp information, if configured. Messages appear in this format:  
seq no:timestamp: %facility-severity-MNEMONIC:description  
The part of the message preceding the percent sign depends on the setting of the service  
sequence-numbers, service timestamps log datetime, service timestamps log datetime [localtime]  
[msec] [show-timezone], or service timestamps log uptime global configuration command.  
Table 20-1 describes the elements of syslog messages.  
System Log Message Elements  
Description  
Table 20-1  
Element  
seq no:  
Stamps log messages with a sequence number only if the service sequence-numbers global  
configuration command is configured.  
For more information, see the “Enabling and Disabling Sequence Numbers in Log Messages”  
section on page 20-8.  
timestamp formats:  
Date and time of the message or event. This information appears only if the service timestamps  
log [datetime | log] global configuration command is configured.  
mm/dd hh:mm:ss  
For more information, see the “Enabling and Disabling Timestamps on Log Messages” section on  
page 20-7.  
or  
hh:mm:ss (short uptime)  
or  
d h (long uptime)  
facility  
The facility to which the message refers (for example, SNMP, SYS, and so forth). For a list of  
supported facilities, see Table 20-4 on page 20-12.  
severity  
Single-digit code from 0 to 7 that is the severity of the message. For a description of the severity  
levels, see Table 20-3 on page 20-9.  
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Chapter 20 Configuring System Message Logging  
Configuring System Message Logging  
Table 20-1  
System Log Message Elements (continued)  
Element  
Description  
MNEMONIC  
description  
Text string that uniquely describes the message.  
Text string containing detailed information about the event being reported.  
This example shows a partial switch system message:  
00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up  
00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet0/17, changed state to up  
00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet0/20, changed state to up  
00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down  
00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/17, changed  
state to down 2  
*Mar 1 18:46:11: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)  
18:47:02: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)  
*Mar 1 18:48:50.483 UTC: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)  
Default System Message Logging Configuration  
Table 20-2 shows the default system message logging configuration.  
Table 20-2  
Default System Message Logging Configuration  
Feature  
Default Setting  
System message logging to the console  
Console severity  
Enabled.  
Debugging (and numerically lower levels; see  
Table 20-3 on page 20-9).  
Logging buffer size  
Logging history size  
Timestamps  
4096 bytes.  
1 message.  
Disabled.  
Synchronous logging  
Logging server  
Disabled.  
Disabled.  
Syslog server IP address  
Server facility  
None configured.  
Local7 (see Table 20-4 on page 20-12).  
Server severity  
Informational (and numerically lower levels; see  
Table 20-3 on page 20-9).  
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Chapter 20 Configuring System Message Logging  
Configuring System Message Logging  
Disabling and Enabling Message Logging  
Message logging is enabled by default. It must be enabled to send messages to any destination other than  
the console. When enabled, log messages are sent to a logging process, which logs messages to  
designated locations asynchronously to the processes that generated the messages.  
Beginning in privileged EXEC mode, follow these steps to disable message logging:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
configure terminal  
Enter global configuration mode.  
Disable message logging.  
Return to privileged EXEC mode.  
Verify your entries.  
no logging console  
end  
show running-config  
or  
show logging  
Step 5  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Disabling the logging process can slow down the switch because a process must wait until the messages  
are written to the console before continuing. When the logging process is disabled, messages appear on  
the console as soon as they are produced, often appearing in the middle of command output.  
The logging synchronous global configuration command also affects the display of messages to the  
console. When this command is enabled, messages appear only after you press Return. For more  
information, see the “Synchronizing Log Messages” section on page 20-6.  
To re-enable message logging after it has been disabled, use the logging on global configuration  
command.  
Setting the Message Display Destination Device  
If message logging is enabled, you can send messages to specific locations in addition to the console.  
Beginning in privileged EXEC mode, use one or more of the following commands to specify the  
locations that receive messages:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
logging buffered [size]  
Log messages to an internal buffer. The default buffer size is 4096. The  
range is 4096 to 4294967295 bytes.  
Note  
Do not make the buffer size too large because the switch could run  
out of memory for other tasks. Use the show memory privileged  
EXEC command to view the free processor memory on the switch;  
however, this value is the maximum available, and the buffer size  
should not be set to this amount.  
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Configuring System Message Logging  
Command  
Purpose  
Step 3  
logging host  
Log messages to a UNIX syslog server host.  
For host, specify the name or IP address of the host to be used as the  
syslog server.  
To build a list of syslog servers that receive logging messages, enter this  
command more than once.  
For complete syslog server configuration steps, see the “Configuring  
UNIX Syslog Servers” section on page 20-10.  
Step 4  
logging file flash:filename  
[max-file-size] [min-file-size]  
[severity-level-number | type]  
Store log messages in a file in flash memory.  
•
•
For filename, enter the log message filename.  
(Optional) For max-file-size, specify the maximum logging file size.  
The range is 4096 to 2147483647. The default is 4069 bytes.  
•
•
(Optional) For min-file-size, specify the minimum logging file size.  
The range is 1024 to 2147483647. The default is 2048 bytes.  
(Optional) For severity-level-number | type, specify either the logging  
severity level or the logging type. The severity range is 0 to 7. For a  
list of logging type keywords, see Table 20-3 on page 20-9. By  
default, the log file receives debugging messages and numerically  
lower levels.  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
terminal monitor  
Log messages to a nonconsole terminal during the current session.  
Terminal parameter-setting commands are set locally and do not remain  
in effect after the session has ended. You must perform this step for each  
session to see the debugging messages.  
Step 7  
Step 8  
show running-config  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
The logging buffered global configuration command copies logging messages to an internal buffer. The  
buffer is circular, so newer messages overwrite older messages after the buffer is full. To display the  
messages that are logged in the buffer, use the show logging privileged EXEC command. The first  
message displayed is the oldest message in the buffer. To clear the contents of the buffer, use the clear  
logging privileged EXEC command.  
To disable logging to the console, use the no logging console global configuration command. To disable  
logging to a file, use the no logging file [severity-level-number | type] global configuration command.  
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Chapter 20 Configuring System Message Logging  
Configuring System Message Logging  
Synchronizing Log Messages  
You can configure the system to synchronize unsolicited messages and debug privileged EXEC  
command output with solicited device output and prompts for a specific service port line or virtual  
terminal line. You can identify the types of messages to be output asynchronously based on the level of  
severity. You can also determine the maximum number of buffers for storing asynchronous messages  
for the terminal after which messages are dropped.  
When synchronous logging of unsolicited messages and debug command output is enabled, unsolicited  
device output appears on the console or is printed after solicited device output appears or is printed.  
Unsolicited messages and debug command output appears on the console after the prompt for user input  
is returned. Therefore, unsolicited messages and debug command output are not interspersed with  
solicited device output and prompts. After the unsolicited messages appear, the console again displays  
the user prompt.  
Beginning in privileged EXEC mode, follow these steps to configure synchronous logging:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
line [console | vty] line-number  
[ending-line-number]  
Specify the line to be configured for synchronous logging of  
messages.  
•
Use the console keyword for configurations that occur through  
the switch service port.  
•
Use the line vty line-number command to specify which vty  
lines are to have synchronous logging enabled. You use a vty  
connection for configurations that occur through a Telnet  
session. The range of line numbers is from 0 to 15.  
You can change the setting of all 16 vty lines at once by entering:  
line vty 0 15  
Or you can change the setting of the single vty line being used for  
your current connection. For example, to change the setting for vty  
line 2, enter:  
line vty 2  
When you enter this command, the mode changes to line  
configuration.  
Step 3  
logging synchronous [level severity-level | Enable synchronous logging of messages.  
all] [limit number-of-buffers]  
•
(Optional) For level severity-level, specify the message severity  
level. Messages with a severity level equal to or higher than this  
value are printed asynchronously. Low numbers mean greater  
severity and high numbers mean lesser severity. The default is 2.  
•
•
(Optional) Specifying level all means that all messages are  
printed asynchronously regardless of the severity level.  
(Optional) For limit number-of-buffers, specify the number of  
buffers to be queued for the terminal after which new messages  
are dropped. The default is 20.  
Step 4  
end  
Return to privileged EXEC mode.  
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Chapter 20 Configuring System Message Logging  
Configuring System Message Logging  
Command  
Purpose  
Step 5  
Step 6  
show running-config  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable synchronization of unsolicited messages and debug output, use the no logging synchronous  
[level severity-level | all] [limit number-of-buffers] line configuration command.  
Enabling and Disabling Timestamps on Log Messages  
By default, log messages are not timestamped.  
Beginning in privileged EXEC mode, follow these steps to enable timestamping of log messages:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Enable log timestamps.  
service timestamps log uptime  
or  
The first command enables timestamps on log messages,  
showing the time since the system was rebooted.  
service timestamps log datetime [msec] [localtime]  
[show-timezone]  
The second command enables timestamps on log messages.  
Depending on the options selected, the timestamp can  
include the date, time in milliseconds relative to the local  
time zone, and the time zone name.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable timestamps for both debug and log messages, use the no service timestamps global  
configuration command.  
This example shows part of a logging display with the service timestamps log datetime global  
configuration command enabled:  
*Mar 1 18:46:11: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)  
This example shows part of a logging display with the service timestamps log uptime global  
configuration command enabled:  
00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up  
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Chapter 20 Configuring System Message Logging  
Configuring System Message Logging  
Enabling and Disabling Sequence Numbers in Log Messages  
Because there is a chance that more than one log message can have the same timestamp, you can display  
messages with sequence numbers so that you can unambiguously see a single message. By default,  
sequence numbers in log messages are not displayed.  
Beginning in privileged EXEC mode, follow these steps to enable sequence numbers in log messages:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
Step 5  
configure terminal  
service sequence-numbers  
end  
Enter global configuration mode.  
Enable sequence numbers.  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To disable sequence numbers, use the no service sequence-numbers global configuration command.  
This example shows part of a logging display with sequence numbers enabled:  
000019: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)  
Defining the Message Severity Level  
You can limit messages displayed to the selected device by specifying the severity level of the message,  
which are described in Table 20-3.  
Beginning in privileged EXEC mode, follow these steps to define the message severity level:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
logging console level  
Limit messages logged to the console.  
By default, the console receives debugging messages and numerically  
lower levels (see Table 20-3 on page 20-9).  
Step 3  
Step 4  
logging monitor level  
logging trap level  
Limit messages logged to the terminal lines.  
By default, the terminal receives debugging messages and numerically  
lower levels (see Table 20-3 on page 20-9).  
Limit messages logged to the syslog servers.  
By default, syslog servers receive informational messages and  
numerically lower levels (see Table 20-3 on page 20-9).  
For complete syslog server configuration steps, see the “Configuring  
UNIX Syslog Servers” section on page 20-10.  
Step 5  
end  
Return to privileged EXEC mode.  
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Chapter 20 Configuring System Message Logging  
Configuring System Message Logging  
Command  
Purpose  
Step 6  
show running-config  
Verify your entries.  
or  
show logging  
Step 7  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Note  
Specifying a level causes messages at that level and numerically lower levels to appear at the destination.  
To disable logging to the console, use the no logging console global configuration command. To disable  
logging to a terminal other than the console, use the no logging monitor global configuration command.  
To disable logging to syslog servers, use the no logging trap global configuration command.  
Table 20-3 describes the level keywords. It also lists the corresponding UNIX syslog definitions from  
the most severe level to the least severe level.  
Table 20-3  
Message Logging Level Keywords  
Level Keyword  
emergencies  
alerts  
Level  
Description  
Syslog Definition  
LOG_EMERG  
LOG_ALERT  
LOG_CRIT  
0
1
2
3
4
5
6
7
System unstable  
Immediate action needed  
Critical conditions  
critical  
errors  
Error conditions  
LOG_ERR  
warnings  
notifications  
informational  
debugging  
Warning conditions  
Normal but significant condition  
Informational messages only  
Debugging messages  
LOG_WARNING  
LOG_NOTICE  
LOG_INFO  
LOG_DEBUG  
The software generates four other categories of messages:  
•
Error messages about software or hardware malfunctions that appear at levels warnings through  
emergencies. These types of messages mean that the functionality of the switch is affected. For  
information on how to recover from these malfunctions, see the system message guide for this  
release.  
•
•
•
Output from the debug commands, displayed at the debugging level. Debug commands are  
typically used only by the Technical Assistance Center.  
Interface up or down transitions and system restart messages, displayed at the notifications level.  
This message is only for information; switch functionality is not affected.  
Reload requests and low-process stack messages, displayed at the informational level. This  
message is only for information; switch functionality is not affected.  
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Chapter 20 Configuring System Message Logging  
Configuring System Message Logging  
Limiting Syslog Messages Sent to the History Table and to SNMP  
If you enabled syslog message traps to be sent to an SNMP network management station by using the  
snmp-server enable trap global configuration command, you can change the level of messages sent and  
stored in the switch history table. You also can change the number of messages that are stored in the  
history table.  
Messages are stored in the history table because SNMP traps are not guaranteed to reach their  
destination. By default, one message of the level warning and numerically lower levels (see Table 20-3  
on page 20-9) are stored in the history table even if syslog traps are not enabled.  
Beginning in privileged EXEC mode, follow these steps to change the level and history table size  
defaults:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
logging history level1  
Enter global configuration mode.  
Change the default level of syslog messages stored in the history file and  
sent to the SNMP server.  
See Table 20-3 on page 20-9 for a list of level keywords.  
By default, warnings, errors, critical, alerts, and emergencies messages  
are sent.  
Step 3  
logging history size number  
Specify the number of syslog messages that can be stored in the history  
table.  
The default is to store one message. The range is 1 to 500 messages.  
Return to privileged EXEC mode.  
Step 4  
Step 5  
Step 6  
end  
show running-config  
Verify your entries.  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
1. Table 20-3 lists the level keywords and severity level. For SNMP usage, the severity level values increase by 1. For example, emergencies  
equal 1, not 0, and critical equals 3, not 2.  
When the history table is full (it contains the maximum number of message entries specified with the  
logging history size global configuration command), the oldest message entry is deleted from the table  
to allow the new message entry to be stored.  
To return the logging of syslog messages to the default level, use the no logging history global  
configuration command. To return the number of messages in the history table to the default value, use  
the no logging history size global configuration command.  
Configuring UNIX Syslog Servers  
The next sections describe how to configure the UNIX server syslog daemon and how to define the  
UNIX system logging facility.  
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Chapter 20 Configuring System Message Logging  
Configuring System Message Logging  
Logging Messages to a UNIX Syslog Daemon  
Before you can send system log messages to a UNIX syslog server, you must configure the syslog  
daemon on a UNIX server. Log in as root, and perform these steps:  
Note  
Some recent versions of UNIX syslog daemons no longer accept by default syslog packets from the  
network. If this is the case with your system, use the UNIX man syslogd command to determine what  
options must be added to or removed from the syslog command line to enable logging of remote syslog  
messages.  
Step 1  
Add a line such as the following to the file /etc/syslog.conf:  
local7.debug /usr/adm/logs/switch.log  
The local7 keyword specifies the logging facility to be used; see Table 20-4 on page 20-12 for  
information on the facilities. The debug keyword specifies the syslog level; see Table 20-3 on page 20-9  
for information on the severity levels. The syslog daemon sends messages at this level or at a more severe  
level to the file specified in the next field. The file must already exist, and the syslog daemon must have  
permission to write to it.  
Step 2  
Step 3  
Create the log file by entering these commands at the UNIX shell prompt:  
$ touch /var/log/switch.log  
$ chmod 666 /var/log/switch.log  
Make sure the syslog daemon reads the new changes:  
$ kill -HUP `cat /etc/syslog.pid`  
For more information, see the man syslog.conf and man syslogd commands on your UNIX system.  
Configuring the UNIX System Logging Facility  
When sending system log messages to an external device, you can cause the switch to identify its  
messages as originating from any of the UNIX syslog facilities.  
Beginning in privileged EXEC mode, follow these steps to configure UNIX system facility message  
logging:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
logging host  
Log messages to a UNIX syslog server host by entering its IP address.  
To build a list of syslog servers that receive logging messages, enter this  
command more than once.  
Step 3  
logging trap level  
Limit messages logged to the syslog servers.  
Be default, syslog servers receive informational messages and lower. See  
Table 20-3 on page 20-9 for level keywords.  
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Chapter 20 Configuring System Message Logging  
Displaying the Logging Configuration  
Command  
Purpose  
Step 4  
logging facility facility-type  
Configure the syslog facility. See Table 20-4 on page 20-12 for  
facility-type keywords.  
The default is local7.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To remove a syslog server, use the no logging host global configuration command, and specify the  
syslog server IP address. To disable logging to syslog servers, enter the no logging trap global  
configuration command.  
Table 20-4 lists the UNIX system facilities supported by the software. For more information about these  
facilities, consult the operator’s manual for your UNIX operating system.  
Table 20-4  
Logging Facility-Type Keywords  
Facility Type Keyword  
auth  
Description  
Authorization system  
Cron facility  
cron  
daemon  
kern  
System daemon  
Kernel  
local0-7  
lpr  
Locally defined messages  
Line printer system  
Mail system  
mail  
news  
USENET news  
System use  
sys9  
sys10  
System use  
sys11  
System use  
sys12  
System use  
sys13  
System use  
sys14  
System use  
syslog  
user  
System log  
User process  
uucp  
UNIX-to-UNIX copy system  
Displaying the Logging Configuration  
To display the logging configuration and the contents of the log buffer, use the show logging privileged  
EXEC command. For information about the fields in this display, see the Cisco IOS Configuration  
Fundamentals Command Reference, Release 12.1.  
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C H A P T E R  
21  
Configuring SNMP  
This chapter describes how to configure the Simple Network Management Protocol (SNMP) on your  
Cisco Systems Intelligent Gigabit Ethernet Switch Module.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the switch  
command reference for this release and to the Cisco IOS Configuration Fundamentals Command  
Reference for Release 12.1.  
This chapter consists of these sections:  
•
•
•
Understanding SNMP, page 21-1  
Configuring SNMP, page 21-5  
Displaying SNMP Status, page 21-15  
Understanding SNMP  
SNMP is an application-layer protocol that provides a message format for communication between  
managers and agents. The SNMP system consists of an SNMP manager, an SNMP agent, and a MIB.  
The SNMP manager can be part of a network management system (NMS) such as CiscoWorks. The  
agent and MIB reside on the switch. To configure SNMP on the switch, you define the relationship  
between the manager and the agent.  
The SNMP agent contains MIB variables whose values the SNMP manager can request or change. A  
manager can get a value from an agent or store a value into the agent. The agent gathers data from the  
MIB, the repository for information about device parameters and network data. The agent can also  
respond to a manager’s requests to get or set data.  
An agent can send unsolicited traps to the manager. Traps are messages alerting the SNMP manager to  
a condition on the network. Traps can mean improper user authentication, restarts, link status (up or  
down), MAC address tracking, closing of a TCP connection, loss of connection to a neighbor, or other  
significant events.  
This section includes information about these topics:  
•
•
•
•
SNMP Versions, page 21-2  
SNMP Manager Functions, page 21-3  
SNMP Agent Functions, page 21-3  
SNMP Community Strings, page 21-4  
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Chapter 21 Configuring SNMP  
Understanding SNMP  
•
•
Using SNMP to Access MIB Variables, page 21-4  
SNMP Notifications, page 21-4  
SNMP Versions  
This software release supports these SNMP versions:  
•
•
SNMPv1—The Simple Network Management Protocol, a Full Internet Standard, defined in  
RFC 1157.  
SNMPv2C replaces the Party-based Administrative and Security Framework of SNMPv2Classic  
with the community-string-based Administrative Framework of SNMPv2C while retaining the bulk  
retrieval and improved error handling of SNMPv2Classic. It has these features:  
–
SNMPv2—Version 2 of the Simple Network Management Protocol, a Draft Internet Standard,  
defined in RFCs 1902 through 1907.  
–
SNMPv2C—The community-string-based Administrative Framework for SNMPv2, an  
Experimental Internet Protocol defined in RFC 1901.  
•
SNMPv3—Version 3 of the SNMP is an interoperable standards-based protocol defined in  
RFCs 2273 to 2275. SNMPv3 provides secure access to devices by authenticating and encrypting  
packets over the network and includes these security features:  
–
–
–
Message integrity—ensuring that a packet was not tampered with in transit  
Authentication—determining that the message is from a valid source  
Encryption—mixing the contents of a package to prevent it from being read by an unauthorized  
source.  
Note  
To select encryption, enter the priv keyword. This keyword is available only when the  
cryptographic (encrypted) software image is installed.  
Both SNMPv1 and SNMPv2C use a community-based form of security. The community of managers  
able to access the agent’s MIB is defined by an IP address access control list and password.  
SNMPv2C includes a bulk retrieval mechanism and more detailed error message reporting to  
management stations. The bulk retrieval mechanism retrieves tables and large quantities of information,  
minimizing the number of round-trips required. The SNMPv2C improved error-handling includes  
expanded error codes that distinguish different kinds of error conditions; these conditions are reported  
through a single error code in SNMPv1. Error return codes in SNMPv2C report the error type.  
SNMPv3 provides for both security models and security levels. A security model is an authentication  
strategy set up for a user and the group within which the user resides. A security level is the permitted  
level of security within a security model. A combination of the security level and the security model  
determine which security mechanism is used when handling an SNMP packet. Available security models  
are SNMPv1, SNMPv2C, and SNMPv3.  
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Chapter 21 Configuring SNMP  
Understanding SNMP  
Table 21-1 identifies the characteristics of the different combinations of security models and levels.  
Table 21-1  
SNMP Security Models and Levels  
Model  
Level  
Authentication  
Encryption Result  
SNMPv1  
noAuthNoPriv  
Community string No  
Community string No  
Uses a community string match for authentication.  
Uses a community string match for authentication.  
Uses a username match for authentication.  
SNMPv2C noAuthNoPriv  
SNMPv3  
SNMPv3  
noAuthNoPriv  
authNoPriv  
Username  
No  
No  
MD5 or SHA  
Provides authentication based on the HMAC-MD5  
or HMAC-SHA algorithms.  
You must configure the SNMP agent to use the SNMP version supported by the management station.  
Because an agent can communicate with multiple managers, you can configure the software to support  
communications using SNMPv1, SNMPv2C, or SNMPv3.  
SNMP Manager Functions  
The SNMP manager uses information in the MIB to perform the operations described in Table 21-2.  
Table 21-2  
SNMP Operations  
Operation  
Description  
get-request  
Retrieves a value from a specific variable.  
Retrieves a value from a variable within a table.1  
get-next-request  
get-bulk-request2 Retrieves large blocks of data, such as multiple rows in a table, that would  
otherwise require the transmission of many small blocks of data.  
get-response  
set-request  
trap  
Replies to a get-request, get-next-request, and set-request sent by an NMS.  
Stores a value in a specific variable.  
An unsolicited message sent by an SNMP agent to an SNMP manager when some  
event has occurred.  
1. With this operation, an SNMP manager does not need to know the exact variable name. A sequential search is performed to  
find the needed variable from within a table.  
2. The get-bulk command only works with SNMPv2 or later.  
SNMP Agent Functions  
The SNMP agent responds to SNMP manager requests as follows:  
•
Get a MIB variable—The SNMP agent begins this function in response to a request from the NMS.  
The agent retrieves the value of the requested MIB variable and responds to the NMS with that  
value.  
•
Set a MIB variable—The SNMP agent begins this function in response to a message from the NMS.  
The SNMP agent changes the value of the MIB variable to the value requested by the NMS.  
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Chapter 21 Configuring SNMP  
Understanding SNMP  
The SNMP agent also sends unsolicited trap messages to notify an NMS that a significant event has  
occurred on the agent. Examples of trap conditions include, but are not limited to, when a port or module  
goes up or down, when spanning-tree topology changes occur, and when authentication failures occur.  
SNMP Community Strings  
SNMP community strings authenticate access to MIB objects and function as embedded passwords. In  
order for the NMS to access the switch, the community string definitions on the NMS must match at least  
one of the three community string definitions on the switch.  
A community string can have one of these attributes:  
•
Read-only (RO)—Gives read access to authorized management stations to all objects in the MIB  
except the community strings, but does not allow write access  
•
Read-write (RW)—Gives read and write access to authorized management stations to all objects in  
the MIB, but does not allow access to the community strings  
Using SNMP to Access MIB Variables  
An example of an NMS is the CiscoWorks network management software. CiscoWorks 2000 software  
uses the switch MIB variables to set device variables and to poll devices on the network for specific  
information. The results of a poll can be displayed as a graph and analyzed to troubleshoot  
internetworking problems, increase network performance, verify the configuration of devices, monitor  
traffic loads, and more.  
As shown in Figure 21-1, the SNMP agent gathers data from the MIB. The agent can send traps, or  
notification of certain events, to the SNMP manager, which receives and processes the traps. Traps alert  
the SNMP manager to a condition on the network such as improper user authentication, restarts, link  
status (up or down), MAC address tracking, and so forth. The SNMP agent also responds to MIB-related  
queries sent by the SNMP manager in get-request, get-next-request, and set-request format.  
Figure 21-1  
SNMP Network  
Get-request, Get-next-request,  
Network device  
NMS  
Get-bulk, Set-request  
MIB  
SNMP Agent  
Get-response, traps  
SNMP Manager  
For information on supported MIBs and how to access them, see Appendix A, “Supported MIBs.”  
SNMP Notifications  
SNMP allows the switch to send notifications to SNMP managers when particular events occur. SNMP  
notifications can be sent as traps or inform requests. In command syntax, unless there is an option in the  
command to select either traps or informs, the keyword traps refers to either traps or informs, or both.  
Use the snmp-server host command to specify whether to send SNMP notifications as traps or informs.  
Note  
SNMPv1 does not support informs.  
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Chapter 21 Configuring SNMP  
Configuring SNMP  
Traps are unreliable because the receiver does not send an acknowledgment when it receives a trap, and  
the sender cannot determine if the trap was received. When an SNMP manager receives an inform  
request, it acknowledges the message with an SNMP response protocol data unit (PDU). If the sender  
does not receive a response, the inform request can be sent again. Because they can be re-sent, informs  
are more likely than traps to reach their intended destination.  
The characteristics that make informs more reliable than traps also consume more resources in the switch  
and in the network. Unlike a trap, which is discarded as soon as it is sent, an inform request is held in  
memory until a response is received or the request times out. Traps are sent only once, but an inform  
might be re-sent or retried several times. The retries increase traffic and contribute to a higher overhead  
on the network. Therefore, traps and informs require a trade-off between reliability and resources. If it  
is important that the SNMP manager receive every notification, use inform requests. If traffic on the  
network or memory in the switch is a concern and notification is not required, use traps.  
Configuring SNMP  
This section describes how to configure SNMP on your switch. It contains this configuration  
information:  
•
•
•
•
•
•
•
•
•
Default SNMP Configuration, page 21-5  
SNMP Configuration Guidelines, page 21-6  
Disabling the SNMP Agent, page 21-6  
Configuring Community Strings, page 21-7  
Configuring SNMP Groups and Users, page 21-8  
Configuring SNMP Notifications, page 21-10  
Setting the Agent Contact and Location Information, page 21-13  
Limiting TFTP Servers Used Through SNMP, page 21-13  
SNMP Examples, page 21-14  
Default SNMP Configuration  
Table 21-3 shows the default SNMP configuration.  
Table 21-3  
Default SNMP Configuration  
Feature  
Default Setting  
SNMP agent  
Enabled.  
SNMP community strings  
Read-Only: Public  
Read-Write: Private  
SNMP trap receiver  
SNMP traps  
None configured.  
None enabled.  
SNMP version  
If no version keyword is present, the default is Version 1.  
SNMPv3 authentication  
If no keyword is entered, the default is the noauth (noAuthNoPriv)  
security level.  
SNMP notification type  
If no type is specified, all notifications are sent.  
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Configuring SNMP  
SNMP Configuration Guidelines  
If the switch starts and the switch startup configuration has at least one snmp-server global  
configuration command, the SNMP agent is enabled.  
An SNMP group is a table that maps SNMP users to SNMP views. An SNMP user is a member of an  
SNMP group. An SNMP host is the recipient of an SNMP trap operation. An SNMP engine ID is a name  
for the local or remote SNMP engine.  
When configuring SNMP, follow these guidelines:  
•
When configuring an SNMP group, do not specify a notify view. The snmp-server host global  
configuration command autogenerates a notify view for the user and then adds it to the group  
associated with that user. Modifying the group's notify view affects all users associated with that  
group. See the Cisco IOS Configuration Fundamentals Command Reference for Release 12.1 for  
information about when you should configure notify views.  
•
•
To configure a remote user, specify the IP address or port number for the remote SNMP agent of the  
device where the user resides.  
Before you configure remote users for a particular agent, configure the SNMP engine ID, using the  
snmp-server engineID global configuration with the remote option. The remote agent's SNMP  
engine ID and user password are used to compute the authentication and privacy digests. If you do  
not configure the remote engine ID first, the configuration command fails.  
•
•
•
When configuring SNMP informs, you need to configure the SNMP engine ID for the remote agent  
in the SNMP database before you can send proxy requests or informs to it.  
If a local user is not associated with a remote host, the switch does not send informs for the auth  
(authNoPriv) and the priv (authPriv) authentication levels.  
Changing the value of the SNMP engine ID has important side effects. A user's password (entered  
on the command line) is converted to an MD5 or SHA security digest based on the password and the  
local engine ID. The command-line password is then destroyed, as required by RFC 2274. Because  
of this deletion, if the value of engineID changes, the security digests of SNMPv3 users become  
invalid, and you need to reconfigure SNMP users by using the snmp-server user username global  
configuration command. Similar restrictions require the reconfiguration of community strings when  
the engine ID changes.  
Disabling the SNMP Agent  
Beginning in privileged EXEC mode, follow these steps to disable the SNMP agent:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
Step 4  
Step 5  
configure terminal  
no snmp-server  
Enter global configuration mode.  
Disable the SNMP agent operation.  
Return to privileged EXEC mode.  
Verify your entries.  
end  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
The no snmp-server global configuration command disables all running versions (Version 1,  
Version 2C, and Version 3) on the device. No specific Cisco IOS command exists to enable SNMP. The  
first snmp-server global configuration command that you enter enables all versions of SNMP.  
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Chapter 21 Configuring SNMP  
Configuring SNMP  
Configuring Community Strings  
You use the SNMP community string to define the relationship between the SNMP manager and the  
agent. The community string acts like a password to permit access to the agent on the switch. Optionally,  
you can specify one or more of these characteristics associated with the string:  
•
An access list of IP addresses of the SNMP managers that are permitted to use the community string  
to gain access to the agent  
•
•
A MIB view, which defines the subset of all MIB objects accessible to the given community  
Read and write or read-only permission for the MIB objects accessible to the community  
Beginning in privileged EXEC mode, follow these steps to configure a community string on the switch:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Configure the community string.  
snmp-server community string [view  
view-name] [ro | rw] [access-list-number]  
•
For string, specify a string that acts like a password and  
permits access to the SNMP protocol. You can configure one  
or more community strings of any length.  
•
•
(Optional) For view, specify the view record accessible to the  
community.  
(Optional) Specify either read-only (ro) if you want  
authorized management stations to retrieve MIB objects, or  
specify read-write (rw) if you want authorized management  
stations to retrieve and modify MIB objects. By default, the  
community string permits read-only access to all objects.  
•
(Optional) For access-list-number, enter an IP standard access  
list numbered from 1 to 99 and 1300 to 1999.  
Step 3  
access-list access-list-number {deny |  
permit} source [source-wildcard]  
(Optional) If you specified an IP standard access list number in  
Step 2, then create the list, repeating the command as many times  
as necessary.  
•
For access-list-number, enter the access list number specified  
in Step 2.  
•
The deny keyword denies access if the conditions are  
matched. The permit keyword permits access if the conditions  
are matched.  
•
•
For source, enter the IP address of the SNMP managers that  
are permitted to use the community string to gain access to the  
agent.  
(Optional) For source-wildcard, enter the wildcard bits in  
dotted decimal notation to be applied to the source. Place ones  
in the bit positions that you want to ignore.  
Recall that the access list is always terminated by an implicit deny  
statement for everything.  
Step 4  
end  
Return to privileged EXEC mode.  
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Chapter 21 Configuring SNMP  
Configuring SNMP  
Command  
Purpose  
Step 5  
Step 6  
show running-config  
Verify your entries.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Note  
To disable access for an SNMP community, set the community string for that community to the null  
string (do not enter a value for the community string).  
To remove a specific community string, use the no snmp-server community string global configuration  
command.  
This example shows how to assign the string comaccess to SNMP, to allow read-only access, and to  
specify that IP access list 4 can use the community string to gain access to the switch SNMP agent:  
Switch(config)# snmp-server community comaccess ro 4  
Configuring SNMP Groups and Users  
You can specify an identification name (engineID) for the local or remote SNMP server engine on the  
switch. You can configure an SNMP server group that maps SNMP users to SNMP views, and you can  
add new users to the SNMP group.  
Beginning in privileged EXEC mode, follow these steps to configure SNMP on the switch:  
Command  
configure terminal  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
snmp-server engineID {local engineid-string Configure a name for either the local or remote copy of SNMP.  
| remote ip-address [udp-port port-number]  
engineid-string}  
•
The engineid-string is a 24-character ID string with the name  
of the copy of SNMP. You need not specify the entire  
24-character engine ID if it contains trailing zeros. Specify  
only the portion of the engine ID up to the point where only  
zeros remain in the value. For example, to configure an engine  
ID of 123400000000000000000000, you can enter this:  
snmp-server engineID local 1234  
•
If you select remote, specify the ip-address of the device that  
contains the remote copy of SNMP and the optional User  
Datagram Protocol (UDP) port on the remote device. The  
default is 162.  
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Chapter 21 Configuring SNMP  
Configuring SNMP  
Command  
Purpose  
Step 3  
snmp-server group groupname {v1 | v2c | v3 Configure a new SNMP group on the remote device.  
{auth | noauth | priv}} [read readview]  
•
•
For groupname, specify the name of the group.  
[write writeview] [notify notifyview] [access  
access-list]  
Specify a security model:  
–
–
v1 is the least secure of the possible security models.  
v2c is the second least secure model. It allows  
transmission of informs and integers twice the normal  
width.  
–
v3, the most secure, requires you to select an  
authentication level:  
auth—Enables the Message Digest 5 (MD5) and the  
Secure Hash Algorithm (SHA) packet authentication.  
noauth—Enables the noAuthNoPriv security level. This  
is the default if no keyword is specified.  
priv—Enables Data Encryption Standard (DES) packet  
encryption (also called privacy).  
Note  
•
The priv keyword is available only when the cryptographic  
software image is installed.  
(Optional) Enter read readview with a string (not to exceed 64  
characters) that is the name of the view in which you can only  
view the contents of the agent.  
•
•
•
(Optional) Enter write writeview with a string (not to exceed  
64 characters) that is the name of the view in which you enter  
data and configure the contents of the agent.  
(Optional) Enter notify notifyview with a string (not to exceed  
64 characters) that is the name of the view in which you  
specify a notify, inform, or trap.  
(Optional) Enter access access-list with a string (not to exceed  
64 characters) that is the name of the access list.  
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Configuring SNMP  
Command  
Purpose  
Step 4  
snmp-server user username groupname  
Add a new user for an SNMP group.  
{remote host [udp-port port]} {v1 [access  
access-list] | v2c [access access-list] | v3  
[encrypted] [access access-list] [auth {md5 |  
sha} auth-password]}  
•
•
•
The username is the name of the user on the host that connects  
to the agent.  
The groupname is the name of the group to which the user is  
associated.  
Enter remote to specify a remote SNMP entity to which the  
user belongs and the hostname or IP address of that entity with  
the optional UDP port number. The default is 162.  
•
Enter the SNMP version number (v1, v2c, or v3). If you enter  
v3, you have these additional options:  
–
encrypted specifies that the password appears in  
encrypted format. This keyword is available only when  
the v3 keyword is specified.  
–
auth is an authentication level setting session that can be  
either the HMAC-MD5-96 (md5) or the HMAC-SHA-96  
(sha) authentication level, and requires a password string  
(not to exceed 64 characters).  
•
(Optional) Enter access access-list with a string (not to exceed  
64 characters) that is the name of the access list.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Configuring SNMP Notifications  
A trap manager is a management station that receives and processes traps. Traps are system alerts that  
the switch generates when certain events occur. By default, no trap manager is defined, and no traps are  
sent. Switches running this Cisco IOS release can have an unlimited number of trap managers.  
Note  
Many commands use the word traps in the command syntax. Unless there is an option in the command  
to select either traps or informs, the keyword traps refers to either traps, informs, or both. Use the  
snmp-server host global configuration command to specify whether to send SNMP notifications as  
traps or informs.  
Table 21-4 describes the supported switch traps (notification types). You can enable any or all of these  
traps and configure a trap manager to receive them.  
Table 21-4  
Switch Notification Types  
Notification Type  
Keyword  
Description  
bridge  
Generates STP bridge MIB traps.  
config  
Generates a trap for SNMP configuration changes.  
Generates a trap for SNMP copy configuration changes.  
copy-config  
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Configuring SNMP  
Table 21-4  
Switch Notification Types (continued)  
Notification Type  
Keyword  
Description  
entity  
Generates a trap for SNMP entity changes.  
envmon  
Generates environmental monitor traps. You can enable any or all of these  
environmental traps: fan, shutdown, status, supply, temperature.  
flash  
Generates SNMP FLASH notifications.  
hsrp  
Generates a trap for Hot Standby Router Protocol (HSRP) changes.  
Generates a trap for MAC address notifications.  
mac-notification  
port-security  
Generates SNMP port security traps. You can also set a maximum trap rate  
per second. The range is from 0 to 1000; the default is 0, which means that  
there is no rate limit.  
rtr  
Generates a trap for the SNMP Response Time Reporter (RTR).  
Generates a trap for SNMP-type notifications.  
Generates SNMP STP Extended MIB traps.  
snmp  
stpx  
syslog  
Generates SNMP syslog traps.  
tty  
Generates a trap for TCP connections. This trap is enabled by default.  
Generates SNMP VLAN-created traps.  
vlancreate  
vlandelete  
vlan-membership  
vtp  
Generates SNMP VLAN-deleted traps.  
Generates a trap for SNMP VLAN membership changes.  
Generates a trap for VLAN Trunking Protocol (VTP) changes.  
You can use the snmp-server host global configuration command to a specific host to receive the  
notification types listed in Table 21-4.  
Beginning in privileged EXEC mode, follow these steps to configure the switch to send traps or informs  
to a host:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
snmp-server engineID remote  
Specify the engine ID for the remote host.  
ip-address engineid-string  
Step 3  
snmp-server user username  
Configure an SNMP user to be associated with the remote host created in  
Step 2.  
groupname {remote host [udp-port  
port]} {v1 [access access-list] | v2c  
[access access-list] | v3 [encrypted]  
[access access-list] [auth {md5 | sha}  
auth-password]}  
Note  
You cannot configure a remote user for an address without first  
configuring the engine ID for the remote host. Otherwise, you  
receive an error message, and the command is not executed.  
Step 4  
snmp-server group [groupname {v1 | Configure an SNMP group.  
v2c | v3 {auth | noauth | priv}}] [read  
readview] [write writeview] [notify  
notifyview] [access access-list]  
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Chapter 21 Configuring SNMP  
Configuring SNMP  
Command  
Purpose  
Specify the recipient of an SNMP trap operation.  
Step 5  
snmp-server host host-addr  
[informs | traps] [version {1 | 2c | 3  
{auth | noauth | priv}}]  
community-string [notification-type]  
•
For host-addr, specify the name or Internet address of the host (the  
targeted recipient).  
•
•
•
(Optional) Enter informs to send SNMP informs to the host.  
(Optional) Enter traps (the default) to send SNMP traps to the host.  
(Optional) Specify the SNMP version (1, 2c, or 3). SNMPv1 is not  
available with informs.  
•
(Optional) For Version 3, select authentication level auth, noauth, or  
priv.  
Note  
The priv keyword is available only when the cryptographic  
software image is installed.  
•
•
For community-string, when version 1 or version 2c is specified,  
enter the password-like community string sent with the notification  
operation. When version 3 is specified, enter the SNMPv3 username.  
(Optional) For notification-type, use the keywords listed in  
Table 21-4 on page 21-10. If no type is specified, all notifications are  
sent.  
Step 6  
Step 7  
snmp-server enable traps  
notification-types  
Enable the switch to send traps or informs and specify the type of  
notifications to be sent. For a list of notification types, see Table 21-4 on  
page 21-10, or enter this: snmp-server enable traps ?  
To enable multiple types of traps, you must enter a separate snmp-server  
enable traps command for each trap type.  
snmp-server trap-source interface-id (Optional) Specify the source interface, which provides the IP address for  
the trap message. This command also sets the source IP address for  
informs.  
Step 8  
Step 9  
snmp-server queue-length length  
snmp-server trap-timeout seconds  
(Optional) Establish the message queue length for each trap host. The  
range is 1 to 1000; the default is 10.  
(Optional) Define how often to resend trap messages. The range is 1 to  
1000; the default is 30 seconds.  
Step 10  
Step 11  
Step 12  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
The snmp-server host command specifies which hosts receive the notifications. The snmp-server  
enable trap command globally enables the mechanism for the specified notification (for traps and  
informs). To enable a host to receive an inform, you must configure an snmp-server host informs  
command for the host and globally enable informs by using the snmp-server enable traps command.  
To remove the specified host from receiving traps, use the no snmp-server host host global  
configuration command. The no snmp-server host command with no keywords disables traps, but not  
informs, to the host. To disable informs, use the no snmp-server host informs global configuration  
command. To disable a specific trap type, use the no snmp-server enable traps notification-types  
global configuration command.  
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Configuring SNMP  
Setting the Agent Contact and Location Information  
Beginning in privileged EXEC mode, follow these steps to set the system contact and location of the  
SNMP agent so that these descriptions can be accessed through the configuration file:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Set the system contact string.  
snmp-server contact text  
For example:  
snmp-server contact Dial System Operator at beeper 21555.  
Set the system location string.  
Step 3  
snmp-server location text  
For example:  
snmp-server location Building 3/Room 222  
Return to privileged EXEC mode.  
Verify your entries.  
Step 4  
Step 5  
Step 6  
end  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Limiting TFTP Servers Used Through SNMP  
Beginning in privileged EXEC mode, follow these steps to limit the TFTP servers used for saving and  
loading configuration files through SNMP to the servers specified in an access list:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
snmp-server tftp-server-list  
access-list-number  
Limit TFTP servers used for configuration file copies through  
SNMP to the servers in the access list.  
For access-list-number, enter an IP standard access list numbered  
from 1 to 99 and 1300 to 1999.  
Step 3  
access-list access-list-number {deny |  
permit} source [source-wildcard]  
Create a standard access list, repeating the command as many times  
as necessary.  
•
For access-list-number, enter the access list number specified  
in Step 2.  
•
The deny keyword denies access if the conditions are matched.  
The permit keyword permits access if the conditions are  
matched.  
•
•
For source, enter the IP address of the TFTP servers that can  
access the switch.  
(Optional) For source-wildcard, enter the wildcard bits, in  
dotted decimal notation, to be applied to the source. Place ones  
in the bit positions that you want to ignore.  
Recall that the access list is always terminated by an implicit deny  
statement for everything.  
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Chapter 21 Configuring SNMP  
Configuring SNMP  
Command  
Purpose  
Step 4  
end  
Return to privileged EXEC mode.  
Verify your entries.  
Step 5  
Step 6  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
SNMP Examples  
This example shows how to enable all versions of SNMP. The configuration permits any SNMP manager  
to access all objects with read-only permissions using the community string public. This configuration  
does not cause the switch to send any traps.  
Switch(config)# snmp-server community public  
This example shows how to permit any SNMP manager to access all objects with read-only permission  
using the community string public. The switch also sends VTP traps to the hosts 192.180.1.111 and  
192.180.1.33 using SNMPv1 and to the host 192.180.1.27 using SNMPv2C. The community string  
public is sent with the traps.  
Switch(config)# snmp-server community public  
Switch(config)# snmp-server enable traps vtp  
Switch(config)# snmp-server host 192.180.1.27 version 2c public  
Switch(config)# snmp-server host 192.180.1.111 version 1 public  
Switch(config)# snmp-server host 192.180.1.33 public  
This example shows how to allow read-only access for all objects to members of access list 4 that use  
the comaccess community string. No other SNMP managers have access to any objects. SNMP  
Authentication Failure traps are sent by SNMPv2C to the host ibm.com using the community string  
public.  
Switch(config)# snmp-server community comaccess ro 4  
Switch(config)# snmp-server enable traps snmp authentication  
Switch(config)# snmp-server host ibm.com version 2c public  
This example shows how to send Entity MIB traps to the host ibm.com. The community string is  
restricted. The first line enables the switch to send Entity MIB traps in addition to any traps previously  
enabled. The second line specifies the destination of these traps and overwrites any previous  
snmp-server host commands for the host ibm.com.  
Switch(config)# snmp-server enable traps entity  
Switch(config)# snmp-server host ibm.com restricted entity  
This example shows how to enable the switch to send all traps to the host myhost.ibm.com using the  
community string public:  
Switch(config)# snmp-server enable traps  
Switch(config)# snmp-server host myhost.ibm.com public  
This example shows how to associate a user with a remote host and to send auth (authNoPriv)  
authentication-level informs when the user enters global configuration mode:  
Switch(config)# snmp-server engineID remote 192.180.1.27 00000063000100a1c0b4011b  
Switch(config)# snmp-server group authgroup v3 auth  
Switch(config)# snmp-server user authuser authgroup remote 192.180.1.27 v3 auth md5  
mypassword  
Switch(config)# snmp-server user authuser authgroup v3 auth md5 mypassword  
Switch(config)# snmp-server host 192.180.1.27 informs version 3 auth authuser config  
Switch(config)# snmp-server enable traps  
Switch(config)# snmp-server inform retries 0  
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Chapter 21 Configuring SNMP  
Displaying SNMP Status  
Displaying SNMP Status  
To display SNMP input and output statistics, including the number of illegal community string entries,  
errors, and requested variables, use the show snmp privileged EXEC command. You also can use the  
other privileged EXEC commands in Table 21-5 to display SNMP information. For information about  
the fields in the displays, see the Cisco IOS Configuration Fundamentals Command Reference for  
Release 12.1  
Table 21-5  
Commands for Displaying SNMP Information  
Feature  
Default Setting  
show snmp  
Displays SNMP statistics.  
show snmp engineID [local | remote] Displays information on the local SNMP engine and all  
remote engines that have been configured on the device.  
show snmp group  
show snmp pending  
show snmp sessions  
show snmp user  
Displays information on each SNMP group on the network.  
Displays information on pending SNMP requests.  
Displays information on the current SNMP sessions.  
Displays information on each SNMP user name in the  
SNMP users table.  
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Displaying SNMP Status  
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C H A P T E R  
22  
Configuring Network Security with ACLs  
This chapter describes how to configure network security on a Cisco Systems Intelligent Gigabit  
Ethernet Switch Module by using access control lists (ACLs), which are also referred to in commands  
and tables as access lists.  
You can create ACLs for physical interfaces or management interfaces. A management interface is  
defined as a management VLAN or any traffic that is going directly to the CPU, such as SNMP, Telnet,  
or web traffic.  
Note  
Note  
An ACLs that applied is to a physical interface has a limitation of one mask, and certain keywords are  
not supported. For more information, see the “Guidelines for Applying ACLs to Physical Interfaces”  
section on page 22-5.  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release and the “Configuring IP Services” section of the Cisco IOS IP and IP Routing  
Configuration Guide, Cisco IOS Release 12.1 and the Cisco IOS IP and IP Routing Command Reference,  
Cisco IOS Release 12.1.  
This chapter consists of these sections:  
•
•
•
•
Understanding ACLs, page 22-2  
Configuring ACLs, page 22-6  
Displaying ACL Information, page 22-20  
Examples for Compiling ACLs, page 22-22  
You can configure ACLs by using the command-line interface (CLI).  
You can also use the security wizard to filter inbound traffic on the switches. Filtering can be based on  
network addresses, TCP applications, or User Datagram Protocol (UDP) applications. You can choose  
whether to drop or to forward packets that meet the filtering criteria. To use this wizard, you must know  
how the network is designed and how interfaces are used on the filtering device. See the security wizard  
online help for step-by-step configuration procedures about using this wizard.  
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Chapter 22 Configuring Network Security with ACLs  
Understanding ACLs  
Understanding ACLs  
Packet filtering can limit network traffic and restrict network use by certain users or devices. ACLs can  
filter traffic as it passes through a switch and permit or deny packets at specified interfaces. An ACL is  
a sequential collection of permit and deny conditions that apply to packets. When a packet is received  
on an interface, the switch compares the fields in the packet against any applied ACLs to verify that the  
packet has the required permissions to be forwarded, based on the criteria specified in the access lists.  
The switch tests the packet against the conditions in an access list one by one. The first match determines  
whether the switch accepts or rejects the packet. Because the switch stops testing conditions after the  
first match, the order of conditions in the list is critical. If no conditions match, the switch rejects the  
packet. If there are no restrictions, the switch forwards the packet; otherwise, the switch drops the  
packet.  
You configure access lists on a Layer 2 switch to provide basic security for your network. If you do not  
configure ACLs, all packets passing through the switch could be allowed onto all parts of the network.  
You can use ACLs to control which hosts can access different parts of a network or to decide which types  
of traffic are forwarded or blocked at switch interfaces. For example, you can allow e-mail traffic to be  
forwarded but not Telnet traffic. ACLs can be configured to block inbound traffic.  
An ACL contains an ordered list of access control entries (ACEs). Each ACE specifies permit or deny  
and a set of conditions the packet must satisfy in order to match the ACE. The meaning of permit or deny  
depends on the context in which the ACL is used.  
The switch supports these types of ACLs on physical interfaces in the inbound direction:  
•
•
•
IP ACLs filter IP, TCP, and UDP traffic.  
Ethernet or MAC ACLs filter Layer 2 traffic.  
MAC extended access lists use source and destination MAC addresses and optional protocol type  
information for matching operations.  
•
•
Standard IP access lists use source addresses for matching operations.  
Extended IP access lists use source and destination addresses and optional protocol type information  
for matching operations.  
The switch examines access lists associated with features configured on a given interface. As packets  
enter the switch on an interface, ACLs associated with all inbound features configured on that interface  
are examined.  
ACLs permit or deny packet forwarding based on how the packet matches the entries in the ACL. For  
example, you can use ACLs to allow one host to access a part of a network, but to prevent another host  
from accessing the same part. In Figure 22-1, ACLs applied at the switch input allow Host A to access  
the Human Resources network, but prevent Host B from accessing the same network.  
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Chapter 22 Configuring Network Security with ACLs  
Understanding ACLs  
Figure 22-1  
Using ACLs to Control Traffic to a Network  
=
=
ACL denying traffic from Server B  
and permitting traffic from Server A  
Packet  
R&D = Research & Development  
HR = Human Resources  
Handling Fragmented and Unfragmented Traffic  
IP packets can be fragmented as they cross the network. When this happens, only the fragment  
containing the beginning of the packet contains the Layer 4 information, such as TCP or UDP port  
numbers, Internet Control Message Protocol (ICMP) type and code, and so on. All other fragments are  
missing this information.  
Some ACEs do not check Layer 4 information and therefore can be applied to all packet fragments.  
ACEs that do test Layer 4 information cannot be applied in the standard manner to most of the fragments  
in a fragmented IP packet. When the fragment contains no Layer 4 information and the ACE tests some  
Layer 4 information, the matching rules are modified:  
•
Permit ACEs that check the Layer 3 information in the fragment (including protocol type, such as  
TCP, UDP, and so on) are considered to match the fragment regardless of what the missing Layer 4  
information might have been.  
•
Deny ACEs that check Layer 4 information never match a fragment unless the fragment contains  
Layer 4 information.  
Consider access list 102, configured with these commands, applied to three fragmented packets:  
Switch (config)# access-list 102 permit tcp any host 10.1.1.1 eq smtp  
Switch (config)# access-list 102 deny tcp any host 10.1.1.2 eq telnet  
Switch (config)# access-list 102 deny tcp any any  
Note  
In the first and second ACEs in the examples, the eq keyword after the destination address means to test  
for the TCP-destination-port well-known numbers equaling Simple Mail Transfer Protocol (SMTP) and  
Telnet, respectively.  
•
Packet A is a TCP packet from host 10.2.2.2, port 65000, going to host 10.1.1.1 on the SMTP port.  
If this packet is fragmented, the first fragment matches the first ACE (a permit), as if it were a  
complete packet because all Layer 4 information is present. The remaining fragments also match the  
first ACE, even though they do not contain the SMTP port information because the first ACE only  
checks Layer 3 information when applied to fragments. (The information in this example is that the  
packet is TCP and that the destination is 10.1.1.1.)  
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Chapter 22 Configuring Network Security with ACLs  
Understanding ACLs  
•
Packet B is from host 10.2.2.2, port 65001, going to host 10.1.1.2 on the Telnet port. If this packet  
is fragmented, the first fragment matches the second ACE (a deny) because all Layer 3 and Layer 4  
information is present. The remaining fragments in the packet do not match the second ACE because  
they are missing Layer 4 information.  
•
•
Because the first fragment was denied, host 10.1.1.2 cannot reassemble a complete packet, so  
packet B is effectively denied. However, the later fragments that are permitted will consume  
bandwidth on the network and the resources of host 10.1.1.2 as it tries to reassemble the packet.  
Fragmented packet C is from host 10.2.2.2, port 65001, going to host 10.1.1.3, port ftp. If this packet  
is fragmented, the first fragment matches the third ACE (a deny). All other fragments also match  
the third ACE because that ACE does not check any Layer 4 information and because Layer 3  
information in all fragments shows that they are being sent to host 10.1.1.3, and the earlier permit  
ACEs were checking different hosts.  
Understanding Access Control Parameters  
Before configuring ACLs on the switches, you must have a thorough understanding of the access control  
parameters (ACPs). ACPs are referred to as masks in the switch CLI commands output.  
Each ACE has a mask and a rule. The Classification Field or mask is the field of interest on which you  
want to perform an action. The specific values associated with a given mask are called rules.  
Packets can be classified on these Layer 2, Layer 3, and Layer 4 fields:  
•
•
Layer 2 fields:  
–
–
–
Source MAC address (Specify all 48 bits.)  
Destination MAC address (Specify all 48 bits.)  
Ethertype (16-bit ethertype field)  
You can use any combination or all of these fields simultaneously to define a flow.  
Layer 3 fields:  
–
IP source address (Specify all 32 IP source address bits to define the flow, or specify an user-  
defined subnet. There are no restrictions on the IP subnet to be specified.)  
–
IP destination address (Specify all 32 IP destination address bits to define the flow, or specify  
an user-defined subnet. There are no restrictions on the IP subnet to be specified.)  
You can use any combination or all of these fields simultaneously to define a flow.  
Layer 4 fields:  
•
–
–
TCP (You can specify a TCP source, destination port number, or both at the same time.)  
UDP (You can specify a UDP source, destination port number, or both at the same time.)  
Note  
A mask can be a combination of either multiple Layer 3 and Layer 4 fields or of multiple Layer 2 fields.  
Layer 2 fields cannot be combined with Layer 3 or Layer 4 fields.  
There are two types of masks:  
•
•
User-defined mask—masks that are defined by the user.  
System-defined mask—these masks can be configured on any interface:  
Switch (config-ext-nacl)# permit tcp any any  
Switch (config-ext-nacl)# deny tcp any any  
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Chapter 22 Configuring Network Security with ACLs  
Understanding ACLs  
Switch (config-ext-nacl)# permit udp any any  
Switch (config-ext-nacl)# deny udp any any  
Switch (config-ext-nacl)# permit ip any any  
Switch (config-ext-nacl)# deny ip any any  
Switch (config-ext-nacl)# deny any any  
Switch (config-ext-nacl)# permit any any  
Note  
In an IP extended ACL (both named and numbered), a Layer 4 system-defined mask cannot  
precede a Layer 3 user-defined mask. For example, a Layer 4 system-defined mask such as  
permit tcp any any or deny udp any any cannot precede a Layer 3 user-defined mask such as  
permit ip 10.1.1.1 any. If you configure this combination, the ACL is not allowed on a Layer 2  
interface. All other combinations of system-defined and user-defined masks are allowed in  
security ACLs.  
The switch ACL configuration is consistent with other Cisco Catalyst switches and Cisco Systems  
Intelligent Gigabit Ethernet Switch Modules. However, there are significant restrictions for configuring  
ACLs on the switches.  
Only four user-defined masks can be defined for the entire system. These can be used for either security  
or quality of service (QoS) but cannot be shared by QoS and security. You can configure as many ACLs  
as you require. However, a system error message appears if ACLs with more than four different masks  
are applied to interfaces. For more information about error messages, see the system message guide for  
this release.  
Table 22-1 lists a summary of the ACL restrictions on the switches.  
Table 22-1  
Summary of ACL Restrictions  
Restriction  
Number  
Number of user-defined masks allowed in an ACL  
Number of ACLs allowed on an interface  
1
1
Total number of user-defined masks for security and QoS allowed on a switch  
Number of rules allowed per mask  
4
16  
Guidelines for Applying ACLs to Physical Interfaces  
When applying ACLs to physical interfaces, follow these configuration guidelines:  
•
Only one ACL with this limitation can be attached to an interface: Gigabit Ethernet ports support up  
to 100 ACEs per 1 ACL per port.  
For more information, see the ip access-group interface command in the command reference for  
this release.  
•
All ACEs in an ACL must have the same user-defined mask. However, ACEs can have different rules  
that use the same mask. On a given interface, only one type of user-defined mask is allowed, but you  
can apply any number of system-defined masks. For more information on system-defined masks, see  
the “Understanding Access Control Parameters” section on page 22-4.  
This example shows the same mask in an ACL:  
Switch (config)# ip access-list extended acl2  
Switch (config-ext-nacl)# permit tcp 10.1.1.1 0.0.0.0 any eq 80  
Switch (config-ext-nacl)# permit tcp 20.1.1.1 0.0.0.0 any eq 23  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
In this example, the first ACE permits all the TCP packets coming from host 10.1.1.1 with a  
destination TCP port number of 80. The second ACE permits all TCP packets coming from host  
20.1.1.1 with a destination TCP port number of 23. Both the ACEs use the same mask; therefore, a  
switch supports this ACL.  
•
When you apply an ACL to a physical interface, some keywords are not supported and certain mask  
restrictions apply to the ACLs. See the “Creating a Numbered Standard ACL” section on page 22-8  
and the “Creating a Numbered Extended ACL” section on page 22-9 for creating these ACLs.  
Note  
You can also apply ACLs to a management interface without the above limitations. For information, see  
the “Configuring IP Services” section of the Cisco IOS IP and IP Routing Configuration Guide, Cisco  
IOS Release 12.1 and the Cisco IOS IP and IP Routing Command Reference, Cisco IOS Release 12.1.  
Configuring ACLs  
This section includes these topics:  
•
•
•
•
“Unsupported Features” section on page 22-6  
“Creating Standard and Extended IP ACLs” section on page 22-7  
“Creating Named MAC Extended ACLs” section on page 22-17  
“Creating MAC Access Groups” section on page 22-18  
Configuring ACLs on a Layer 2 interface is the same as configuring ACLs on Cisco routers. The process  
is briefly described here. For more detailed information about configuring router ACLs, see the  
“Configuring IP Services” chapter in the Cisco IP and IP Routing Configuration Guide, Cisco IOS  
Release 12.1. For detailed information about the commands, see the Cisco IOS IP and IP Routing  
Command Reference, Cisco IOS Release 12.1. For a list of Cisco IOS features not supported on the  
switch, see the “Unsupported Features” section on page 22-6.  
Unsupported Features  
The switch does not support these Cisco IOS router ACL-related features:  
•
•
•
•
•
•
•
•
•
•
Non-IP protocol ACLs (see Table 22-2 on page 22-7)  
Bridge-group ACLs  
IP accounting  
ACL support on the outbound direction  
Inbound and outbound rate limiting (except with QoS ACLs)  
IP packets that have a header length of less than 5 bytes  
Reflexive ACLs  
Dynamic ACLs  
ICMP-based filtering  
Interior Gateway Routing Protocol (IGMP)-based filtering  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
Creating Standard and Extended IP ACLs  
This section describes how to create switch IP ACLs. The switch tests packets against the conditions in  
an access list one by one. The first match determines whether the switch accepts or rejects the packet.  
Because the switch stops testing conditions after the first match, the order of the conditions is critical.  
If no conditions match, the switch denies the packet.  
Follow these steps to use ACLs:  
Step 1  
Step 2  
Create an ACL by specifying an access list number or name and access conditions.  
Apply the ACL to interfaces or terminal lines.  
The software supports these kinds of IP access lists:  
•
•
Standard IP access lists use source addresses for matching operations.  
Extended IP access lists use source and destination addresses for matching operations and optional  
protocol-type information for finer granularity of control.  
Note  
MAC extended access list use source and destination MAC addresses and optional protocol type  
information for matching operations. For more information, see the “Creating Named MAC Extended  
ACLs” section on page 22-17.  
The next sections describe access lists and the steps for using them.  
ACL Numbers  
The number you use to denote your ACL shows the type of access list that you are creating. Table 22-2  
lists the access list number and corresponding type and shows whether or not they are supported by the  
switch. The switch supports IP standard and IP extended access lists, numbers 1 to 199 and 1300 to 2699.  
Table 22-2  
Access List Numbers  
ACL Number  
1–99  
Type  
Supported  
Yes  
Yes  
No  
IP standard access list  
IP extended access list  
Protocol type-code access list  
DECnet access list  
100–199  
200–299  
300–399  
400–499  
500–599  
600–699  
700–799  
800–899  
900–999  
1000–1099  
1100–1199  
No  
XNS standard access list  
XNS extended access list  
AppleTalk access list  
No  
No  
No  
48-bit MAC address access list  
IPX standard access list  
IPX extended access list  
IPX SAP access list  
No  
No  
No  
No  
Extended 48-bit MAC address access list  
No  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
Table 22-2  
Access List Numbers (continued)  
ACL Number  
1200–1299  
1300–1999  
2000–2699  
Type  
Supported  
No  
IPX summary address access list  
IP standard access list (expanded range)  
IP extended access list (expanded range)  
Yes  
Yes  
Note  
In addition to numbered standard and extended ACLs, you can also create named standard and extended  
IP ACLs by using the supported numbers. That is, the name of a standard IP ACL can be 1 to 99; the  
name of an extended IP ACL can be 100 to 199. The advantage of using named ACLs instead of  
numbered lists is that you can delete individual entries from a named list.  
Creating a Numbered Standard ACL  
Note  
For information about creating ACLs to apply to a management interface, see the “Configuring IP  
Services” section of the Cisco IOS IP and IP Routing Configuration Guide, Cisco IOS Release 12.1 and  
the Cisco IOS IP and IP Routing Command Reference, Cisco IOS Release 12.1. You can these apply  
these ACLs only to a management interface.  
Beginning in privileged EXEC mode, follow these steps to create a numbered standard IP ACL:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
access-list access-list-number {deny | permit | Define a standard IP ACL by using a source address and wildcard.  
remark} {source source-wildcard | host source  
| any}  
The access-list-number is a decimal number from 1 to 99 or 1300  
to 1999.  
Enter deny or permit to specify whether to deny or permit access  
if conditions are matched.  
The source is the source address of the network or host from which  
the packet is being sent:  
•
•
The 32-bit quantity in dotted-decimal format.  
The keyword any as an abbreviation for source and  
source-wildcard of 0.0.0.0 255.255.255.255. You do not need  
to enter a source wildcard.  
•
The keyword host as an abbreviation for source and  
source-wildcard of source 0.0.0.0.  
(Optional) The source-wildcard applies wildcard bits to the  
source. (See first bullet item.)  
Note  
The log option is not supported on the switches.  
Step 3  
end  
Return to privileged EXEC mode.  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
Command  
Purpose  
Step 4  
Step 5  
show access-lists [number | name]  
Show the access list configuration.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
Use the no access-list access-list-number global configuration command to delete the entire ACL. You  
cannot delete individual ACEs from numbered access lists.  
Note  
When creating an ACL, remember that, by default, the end of the ACL contains an implicit deny  
statement for all packets that it did not find a match for before reaching the end. With standard access  
lists, if you omit the mask from an associated IP host address ACL specification, 0.0.0.0 is assumed to  
be the mask.  
This example shows how to create a standard ACL to deny access to IP host 171.69.198.102, permit  
access to any others, and display the results.  
Switch (config)# access-list 2 deny host 171.69.198.102  
Switch (config)# access-list 2 permit any  
Switch(config)# end  
Switch# show access-lists  
Standard IP access list 2  
deny  
171.69.198.102  
permit any  
Creating a Numbered Extended ACL  
Although standard ACLs use only source addresses for matching, you can use an extended ACL source  
and destination addresses for matching operations and optional protocol type information for finer  
granularity of control. Some protocols also have specific parameters and keywords that apply to that  
protocol.  
These IP protocols are supported on physical interfaces (protocol keywords are in parentheses in bold):  
Internet Protocol (ip), Transmission Control Protocol (tcp), or User Datagram Protocol (udp).  
Supported parameters can be grouped into these categories:  
•
•
TCP  
UDP  
Table 22-3 lists the possible filtering parameters for ACEs for each protocol type.  
Table 22-3 Filtering Parameter ACEs Supported by Different IP Protocols  
Filtering Parameter1  
Layer 3 Parameters:  
TCP  
UDP  
IP type of service (ToS) byte2  
Differentiated Services Code Point (DSCP)  
IP source address  
–
–
X
X
X
–
X
X
X
–
IP destination address  
Fragments  
TCP or UDP  
X
X
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
Table 22-3  
Filtering Parameter ACEs Supported by Different IP Protocols (continued)  
Filtering Parameter1  
Layer 4 Parameters  
Source port operator  
Source port  
TCP  
UDP  
X
X
X
X
–
X
X
X
X
–
Destination port operator  
Destination port  
TCP flag  
1. X in a protocol column means support for the filtering parameter.  
2. No support for type of service (ToS) minimize monetary cost bit.  
For more details about the specific keywords relative to each protocol, see the Cisco IP and IP Routing  
Command Reference, Cisco IOS Release 12.1.  
Note  
The switch does not support dynamic or reflexive access lists. It also does not support filtering based on  
the minimize-monetary-cost type of service (ToS) bit.  
When creating ACEs in numbered extended access lists, remember that after you create the list, any  
additions are placed at the end of the list. You cannot reorder the list or selectively add or remove ACEs  
from a numbered list.  
Note  
For information about creating ACLs to apply to management interfaces, see the “Configuring IP  
Services” section of Cisco IOS IP and IP Routing Configuration Guide, Release 12.1 and the Cisco IOS  
IP and IP Routing Command Reference, Cisco IOS Release 12.1. You can apply ACLs only to a  
management interface or the CPU, such as SNMP, Telnet, or web traffic.  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
Beginning in privileged EXEC mode, follow these steps to create an extended ACL:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Define an extended IP access list and the access conditions.  
access-list access-list-number  
{deny | permit | remark} protocol  
{source source-wildcard | host  
source | any} [operator port]  
{destination destination-wildcard |  
host destination | any} [operator  
port] [dscp dscp-value]  
The access-list-number is a decimal number from 100 to 199 or 2000 to 2699.  
Enter deny or permit to specify whether to deny or permit the packet if  
conditions are matched.  
For protocol, enter the name or number of an IP protocol: IP, TCP, or UDP. To  
match any Internet protocol (including TCP and UDP), use the keyword ip.  
[time-range time-range-name]  
The source is the number of the network or host from which the packet is sent.  
The source-wildcard applies wildcard bits to the source.  
The destination is the network or host number to which the packet is sent.  
Define a destination or source port.  
•
•
The operator can be only eq (equal).  
If operator is after source source-wildcard, conditions match when the  
source port matches the defined port.  
•
•
If operator is after destination destination-wildcard, conditions match  
when the destination port matches the defined port.  
The port is a decimal number or name of a TCP or UDP port. The number  
can be from 0 to 65535.  
•
•
Use TCP port names only for TCP traffic.  
Use UDP port names only for UDP traffic.  
The destination-wildcard applies wildcard bits to the destination.  
Source, source-wildcard, destination, and destination-wildcard can be  
access-list access-list-number  
{deny | permit | remark} protocol specified in three ways:  
{source source-wildcard | host  
•
•
The 32-bit quantity in dotted-decimal format.  
source | any} [operator port]  
{destination destination-wildcard |  
host destination | any} [operator  
port] [dscp dscp-value]  
The keyword any as an abbreviation for source and source-wildcard  
of 0.0.0.0 255.255.255.255 or any source host.  
•
The keyword host, followed by the 32-bit quantity in dotted-decimal  
format, as an abbreviation for a single host with source and  
source-wildcard of source 0.0.0.0.  
[time-range time-range-name]  
(continued)  
dscp—Enter to match packets with any of the supported 13 DSCP values  
(0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48, and 56), or use the question mark  
(?) to see a list of available values.  
The time-range keyword is optional. For an explanation of this keyword, see  
the “Applying Time Ranges to ACLs” section on page 22-14.  
Step 3  
Step 4  
show access-lists [number | name] Verify the access list configuration.  
copy running-config  
startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
Use the no access-list access-list-number global configuration command to delete the entire access list.  
You cannot delete individual ACEs from numbered access lists.  
This example shows how to create and display an extended access list to deny Telnet access from any  
host in network 171.69.198.0 to any host in network 172.20.52.0 and permit any others. (The eq keyword  
after the destination address means to test for the TCP destination port number equaling Telnet.)  
Switch(config)# access-list 102 deny tcp 171.69.198.0 0.0.0.255 172.20.52.0 0.0.0.255 eq  
telnet  
Switch(config)# access-list 102 permit tcp any any  
Switch(config)# end  
Switch# show access-lists  
Extended IP access list 102  
deny tcp 171.69.198.0 0.0.0.255 172.20.52.0 0.0.0.255 eq telnet  
permit tcp any any  
After an ACL is created, any additions (possibly entered from the terminal) are placed at the end of the  
list. You can add ACEs to an ACL, but deleting any ACE deletes the entire ACL.  
Note  
When creating an ACL, remember that, by default, the end of the access list contains an implicit deny  
statement for all packets if the access list does not find a match before reaching the end. With standard  
access lists, if you omit the mask from an associated IP host address ACL specification, 0.0.0.0 is  
assumed to be the mask.  
After creating an ACL, you must apply it to a line or interface, as described in the “Applying ACLs to  
Terminal Lines or Physical Interfaces” section on page 22-18.  
Creating Named Standard and Extended ACLs  
You can identify IP ACLs with an alphanumeric string (a name) rather than a number. You can use named  
ACLs to configure more IP access lists on a switch than if you use numbered access lists. If you identify  
your access list with a name rather than a number, the mode and command syntax are slightly different.  
However, not all commands that use IP access lists accept a named ACL.  
Note  
The name you give to a standard ACL or extended ACL can also be a number in the supported range of  
access list numbers. That is, the name of a standard IP ACL can be 1 to 99; the name of an extended IP  
ACL can be 100 to 199. The advantage of using named ACLs instead of numbered lists is that you can  
delete individual entries from a named list.  
Consider these guidelines and limitations before configuring named ACLs:  
•
•
A standard ACL and an extended ACL cannot have the same name.  
Numbered ACLs are also available, as described in the “Creating Standard and Extended IP ACLs”  
section on page 22-7.  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
Beginning in privileged EXEC mode, follow these steps to create a standard named access list using  
names:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ip access-list standard {name |  
access-list-number}  
Define a standard IP access list by using a name, and enter  
access-list configuration mode.  
Note  
The name can be a number from 1 to 99.  
Step 3  
deny {source source-wildcard | host source |  
any}  
In access-list configuration mode, specify one or more conditions  
denied or permitted to determine if the packet is forwarded or  
dropped.  
or  
•
host source represents a source and source-wildcard of source  
0.0.0.0.  
permit {source source-wildcard | host source |  
any}  
•
any represents a source and source-wildcard of 0.0.0.0  
255.255.255.255.  
Note  
The log option is not supported on the switches.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show access-lists [number | name]  
copy running-config startup-config  
Show the access list configuration.  
(Optional) Save your entries in the configuration file.  
Beginning in privileged EXEC mode, follow these steps to create an extended named ACL using names:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
ip access-list extended {name |  
access-list-number}  
Define an extended IP access list by using a name, and enter  
access-list configuration mode.  
Note  
The name can be a number from 100 to 199.  
Step 3  
{deny | permit} protocol  
{source source-wildcard | host source | any}  
[operator port] {destination  
destination-wildcard | host destination | any}  
[operator port] [dscp dscp-value] [time-range  
time-range-name]  
In access-list configuration mode, specify the conditions allowed  
or denied.  
See the “Creating a Numbered Extended ACL” section on  
page 22-9 for definitions of protocols and other keywords.  
•
host source represents a source and source-wildcard of source  
0.0.0.0, and host destination represents a destination and  
destination-wildcard of destination 0.0.0.0.  
•
any represents a source and source-wildcard or destination  
and destination-wildcard of 0.0.0.0 255.255.255.255.  
dscp—Enter to match packets with any of the supported 13 DSCP  
values ( 0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48, and 56), or use  
the question mark (?) to see a list of available values.  
The time-range keyword is optional. For an explanation of this  
keyword, see the “Applying Time Ranges to ACLs” section on  
page 22-14.  
Step 4  
end  
Return to privileged EXEC mode.  
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Configuring ACLs  
Command  
Purpose  
Step 5  
Step 6  
show access-lists [number | name]  
Show the access list configuration.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
When making the standard and extended ACL, remember that, by default, the end of the ACL contains  
an implicit deny statement for everything if it did not find a match before reaching the end. For standard  
ACLs, if you omit the mask from an associated IP host address access list specification, 0.0.0.0 is  
assumed to be the mask.  
After you create an ACL, any additions are placed at the end of the list. You cannot selectively add ACEs  
to a specific ACL. However, you can use no permit and no deny commands to remove ACEs from a  
named ACL. This example shows how you can delete individual ACEs from a named ACL:  
Switch(config)# ip access-list extended border-list  
Switch(config-ext-nacl)# no permit ip host 10.1.1.3 any  
Being able to selectively remove lines from a named ACL is one reason you might use named ACLs  
instead of numbered ACLs.  
After creating an ACL, you must apply it to a line or interface, as described in the “Applying ACLs to  
Terminal Lines or Physical Interfaces” section on page 22-18.  
Applying Time Ranges to ACLs  
You can implement extended ACLs based on the time of day and week by using the time-range global  
configuration command. First, define the name and times of the day and week of the time range, and then  
reference the time range by name in an ACL to apply restrictions to the access list. You can use the time  
range to define when the permit or deny statements in the ACL are in effect. The time-range keyword  
and argument are referenced in the named and numbered extended ACL task tables in the “Creating  
Standard and Extended IP ACLs” section on page 22-7, and the “Creating Named Standard and  
Extended ACLs” section on page 22-12.  
These are some of the many benefits of using time ranges:  
•
You have more control over permitting or denying a user access to resources, such as an application  
(identified by an IP address mask pair and a port number).  
•
You can control logging messages. ACL entries can log traffic at certain times of the day, but not  
constantly. Therefore, you can simply deny access without having to analyze many logs generated  
during peak hours.  
Note  
The time range relies on the switch system clock. Therefore, you need a reliable clock source. We  
recommend that you use Network Time Protocol (NTP) to synchronize the switch clock. For more  
information, see the “Managing the System Time and Date” section on page 4-1.  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
Beginning in privileged EXEC mode, follow these steps to configure a time-range parameter for an  
ACL:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
time-range time-range-name  
Identify the time-range by a meaningful name (for example, workhours),  
and enter time-range configuration mode. The name cannot contain a  
space or quotation mark and must begin with a letter.  
Step 3  
absolute [start time date]  
[end time date]  
Specify when the function it will be applied to is operational. Use some  
combination of these commands; multiple periodic statements are  
allowed; only one absolute statement is allowed. If more than one  
absolute statement is configured, only the one configured last is executed.  
or  
periodic day-of-the-week hh:mm to  
[day-of-the-week] hh:mm  
or  
periodic {weekdays | weekend | daily}  
hh:mm to hh:mm  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show time-range  
Verify the time-range configuration.  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To remove a configured time-range, use the no time-range time-range-name global configuration  
command.  
Repeat the steps if you have multiple items that you want operational at different times.  
This example shows how to configure time ranges for workhours and for company holidays and how to  
verify your configuration.  
Switch(config)# time-range workhours  
Switch(config-time-range)# periodic weekdays 8:00 to 12:00  
Switch(config-time-range)# periodic weekdays 13:00 to 17:00  
Switch(config-time-range)# exit  
Switch(config)# time-range new_year_day_2000  
Switch(config-time-range)# absolute start 00:00 1 Jan 2000 end 23:59 1 Jan 2000  
Switch(config-time-range)# exit  
Switch(config)# time-range thanksgiving_2000  
Switch(config-time-range)# absolute start 00:00 22 Nov 2000 end 23:59 23 Nov 2000  
Switch(config-time-range)# exit  
Switch(config)# time-range christmas_2000  
Switch(config-time-range)# absolute start 00:00 24 Dec 2000 end 23:50 25 Dec 2000  
Switch(config-time-range)# end  
Switch# show time-range  
time-range entry: christmas_2000 (inactive)  
absolute start 00:00 24 December 2000 end 23:50 25 December 2000  
time-range entry: new_year_day_2000 (inactive)  
absolute start 00:00 01 January 2000 end 23:59 01 January 2000  
time-range entry: thanksgiving_2000 (inactive)  
absolute start 00:00 22 November 2000 end 23:59 23 November 2000  
time-range entry: workhours (inactive)  
periodic weekdays 8:00 to 12:00  
periodic weekdays 13:00 to 17:00  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
To apply a time range, you must reference it by name (for example, workhours) in an extended ACL that  
can implement time ranges. This example shows how to create and verify extended access list 188 that  
denies TCP traffic from any source to any destination during the defined holiday time ranges and permits  
all TCP traffic during work hours.  
Switch(config)# access-list 188 deny tcp any any time-range new_year_day_2000  
Switch(config)# access-list 188 deny tcp any any time-range thanskgiving_2000  
Switch(config)# access-list 188 deny tcp any any time-range christmas_2000  
Switch(config)# access-list 188 permit tcp any any time-range workhours  
Switch(config)# end  
Switch# show access-lists  
Extended IP access list 188  
deny tcp any any time-range new_year_day_2000 (inactive)  
deny tcp any any time-range thanskgiving_2000 (active)  
deny tcp any any time-range christmas_2000 (inactive)  
permit tcp any any time-range workhours (inactive)  
This example uses named ACLs to permit and deny the same traffic.  
Switch(config)# ip access-list extended deny_access  
Switch(config-ext-nacl)# deny tcp any any time-range new_year_day_2000  
Switch(config-ext-nacl)# deny tcp any any time-range thanksgiving_2000  
Switch(config-ext-nacl)# deny tcp any any time-range christmas_2000  
Switch(config-ext-nacl)# exit  
Switch(config)# ip access-list extended may_access  
Switch(config-ext-nacl)# permit tcp any any time-range workhours  
Switch(config-ext-nacl)# end  
Switch# show ip access-lists  
Extended IP access list deny_access  
deny tcp any any time-range new_year_day_2000 (inactive)  
deny tcp any any time-range thanksgiving_2000 (inactive)  
deny tcp any any time-range christmas_2000 (inactive)  
Extended IP access list may_access  
permit tcp any any time-range workhours (inactive)  
Including Comments About Entries in ACLs  
You can use the remark command to include comments (remarks) about entries in any IP standard or  
extended ACL. The remarks make the ACL easier for you to understand and scan. Each remark line is  
limited to 100 characters.  
The remark can go before or after a permit or deny statement. You should be consistent about where you  
put the remark so that it is clear which remark describes which permit or deny statement. For example,  
it would be confusing to have some remarks before the associated permit or deny statements and some  
remarks after the associated statements.  
For IP numbered standard or extended ACLs, use the access-list access-list number remark remark  
global configuration command to include a comment about an access list. To remove the remark, use the  
no form of this command.  
In this example, the workstation belonging to Jones is allowed access, and the workstation belonging to  
Smith is not allowed access:  
Switch(config)# access-list 1 remark Permit only Jones workstation through  
Switch(config)# access-list 1 permit 171.69.2.88  
Switch(config)# access-list 1 remark Do not allow Smith workstation through  
Switch(config)# access-list 1 deny 171.69.3.13  
For an entry in a named IP ACL, use the remark access-list global configuration command. To remove  
the remark, use the no form of this command.  
In this example, the Jones subnet is not allowed to use outbound Telnet:  
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Chapter 22 Configuring Network Security with ACLs  
Configuring ACLs  
Switch(config)# ip access-list extended telnetting  
Switch(config-ext-nacl)# remark Do not allow Jones subnet to telnet out  
Switch(config-ext-nacl)# deny tcp host 171.69.2.88 any eq telnet  
Creating Named MAC Extended ACLs  
You can filter Layer 2 traffic on a physical Layer 2 interface by using MAC addresses and named MAC  
extended ACLs. The procedure is similar to that of configuring other extended named access lists.  
Note  
Named MAC extended ACLs are used as a part of the mac access-group privileged EXEC command.  
For more information about the supported non-IP protocols in the mac access-list extended command,  
see the command reference for this release.  
Note  
Matching on any SNAP-encapsulated packet with a nonzero Organizational Unique Identifier (OUI) is  
not supported.  
Beginning in privileged EXEC mode, follow these steps to create a named MAC extended ACL:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
Enter global configuration mode.  
mac access-list extended name  
Define an extended MAC access list by using a name.  
{deny | permit} {any | host source MAC  
In extended MAC access-list configuration mode, specify to  
address} {any | host destination MAC address} permit or deny any source MAC address or a specific host source  
[aarp | amber | appletalk | dec-spanning |  
decnet-iv | diagnostic | dsm | etype-6000 |  
etype-8042 | lat | lavc-sca | mop-console |  
mop-dump | msdos | mumps | netbios |  
vines-echo |vines-ip | xns-idp]  
MAC address and any destination MAC address.  
(Optional) You can also enter these options:  
aarp | amber | appletalk | dec-spanning | decnet-iv |  
diagnostic | dsm | etype-6000 | etype-8042 | lat | lavc-sca |  
mop-console | mop-dump | msdos | mumps | netbios |  
vines-echo |vines-ip | xns-idp—(a non-IP protocol).  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show access-lists [number | name]  
copy running-config startup-config  
Show the access list configuration.  
(Optional) Save your entries in the configuration file.  
Use the no mac access-list extended name global configuration command to delete the entire ACL. You  
can also delete individual ACEs from named MAC extended ACLs.  
This example shows how to create and display an access list named mac1, denying only EtherType  
DECnet Phase IV traffic, but permitting all other types of traffic.  
Switch(config)# mac access-list extended mac1  
Switch(config-ext-macl)# deny any any decnet-iv  
Switch(config-ext-macl)# permit any any  
Switch(config-ext-macl)# end  
Switch # show access-list  
Extended MAC access list mac1  
deny  
any any decnet-iv  
permit any any  
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Chapter 22 Configuring Network Security with ACLs  
Applying ACLs to Terminal Lines or Physical Interfaces  
Creating MAC Access Groups  
Beginning in privileged EXEC mode, follow these steps to create MAC access groups and to apply a  
MAC access list to an interface:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Identify a specific interface for configuration, and enter interface  
configuration mode.  
The interface must be a Layer 2 interface.  
Step 3  
Step 4  
Step 5  
Step 6  
mac access-group {name} {in}  
end  
Control access to the specified interface by using the MAC access list name.  
Return to privileged EXEC mode.  
show mac-access group  
Display the MAC ACLs applied on the switch.  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
This example shows how to apply ACL 2 on an interface to filter packets entering the interface:  
Switch(config)# interface gigabitethernet0/17  
Router(config-if)# mac access-group 2 in  
Note  
The mac access-group interface configuration command is only valid when applied to a Layer 2  
interface.  
For inbound ACLs, after receiving a packet, the switch checks the packet against the ACL. If the ACL  
permits the packet, the switch continues to process the packet. If the ACL rejects the packet, the switch  
discards the packet. The MAC ACL applies to both IP and non-IP packets.  
When you apply an undefined ACL to an interface, the switch acts as if the ACL has not been applied  
to the interface and permits all packets. Remember this behavior if you use undefined ACLs as a means  
of network security.  
Applying ACLs to Terminal Lines or Physical Interfaces  
Note  
Before applying an ACL to a physical interface, see the “Guidelines for Applying ACLs to Physical  
Interfaces” section on page 22-5.  
You can apply ACLs to any management interface. For information on creating ACLs on management  
interfaces, see the “Configuring IP Services” section of the Cisco IOS IP and IP Routing Configuration  
Guide, Cisco IOS Release 12.1 and the Cisco IOS IP and IP Routing Command Reference, Cisco IOS  
Release 12.1.  
Note  
The limitations that apply to ACLs on physical interfaces do not apply to ACLs on management  
interfaces.  
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Chapter 22 Configuring Network Security with ACLs  
Applying ACLs to Terminal Lines or Physical Interfaces  
After you create an ACL, you can apply it to one or more management interfaces or terminal lines. ACLs  
can be applied on inbound interfaces. This section describes how to accomplish this task for both  
terminal lines and network interfaces. Note these guidelines:  
•
•
•
When controlling access to a line, you must use numbered IP ACLs or MAC extended ACLs.  
When controlling access to an interface, you can use named or numbered ACLs.  
Set identical restrictions on all the virtual terminal lines because a user can attempt to connect to  
any of them.  
•
If you apply ACLs to a management interface, the ACL only filters packets that are intended for the  
CPU, such as SNMP, Telnet, or web traffic.  
Applying ACLs to a Terminal Line  
Beginning in privileged EXEC mode, follow these steps to restrict incoming connections between a  
virtual terminal line and the addresses in an ACL:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
line [console | vty] line-number  
Identify a specific line for configuration, and enter in-line configuration  
mode.  
Enter console for the console terminal line. The service port is DCE.  
Enter vty for a virtual terminal for remote console access.  
The line-number is the first line number in a contiguous group that you want  
to configure when the line type is specified. The range is from 0 to 16.  
Step 3  
access-class access-list-number {in} Restrict incoming and outgoing connections between a particular virtual  
terminal line (into a device) and the addresses in an access list.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Display the access list configuration.  
show running-config  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
Applying ACLs to a Physical Interface  
Beginning in privileged EXEC mode, follow these steps to control access to a Layer 2 interface:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
interface interface-id  
Enter global configuration mode.  
Identify a specific interface for configuration and enter interface  
configuration mode.  
The interface must be a Layer 2 or management interface or a management  
interface VLAN ID.  
Step 3  
Step 4  
ip access-group {access-list-number | Control access to the specified interface.  
name} {in}  
end  
Return to privileged EXEC mode.  
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Chapter 22 Configuring Network Security with ACLs  
Displaying ACL Information  
Command  
Purpose  
Display the access list configuration.  
Step 5  
Step 6  
show running-config  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
This example shows how to apply access list 2 on an interface to filter packets entering the interface:  
Switch(config)# interface gigabitethernet0/20  
Router(config-if)# ip access-group 2 in  
Note  
The ip access-group interface configuration command is only valid when applied to a management  
interface or a Layer 2 physical interface. ACLs cannot be applied to interface port-channels.  
For inbound ACLs, after receiving a packet, the switch checks the packet against the ACL. If the ACL  
permits the packet, the switch continues to process the packet. If the ACL rejects the packet, the switch  
discards the packet.  
When you apply an undefined ACL to an interface, the switch acts as if the ACL has not been applied  
to the interface and permits all packets. Remember this behavior if you use undefined ACLs for network  
security.  
Displaying ACL Information  
You can display the ACLs that are configured on the switch, and you can display the ACLs that have  
been applied to physical and management interfaces. This section consists of these topics:  
•
•
Displaying ACLs, page 22-20  
Displaying Access Groups, page 22-21  
Displaying ACLs  
You can display existing ACLs by using show commands.  
Beginning in privileged EXEC mode, follow these steps to display access lists:  
Command  
Purpose  
Step 1  
Step 2  
show access-lists [number | name]  
Show information about all IP and MAC address access lists or about a  
specific access list (numbered or named).  
show ip access-list [number | name]  
Show information about all IP address access lists or about a specific IP  
ACL (numbered or named).  
This example shows all standard and extended ACLs:  
Switch# show access-lists  
Standard IP access list 1  
permit 172.20.10.10  
Standard IP ACL 10  
permit 12.12.12.12  
Standard IP access list 12  
deny 1.3.3.2  
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Chapter 22 Configuring Network Security with ACLs  
Displaying ACL Information  
Standard IP access list 32  
permit 172.20.20.20  
Standard IP access list 34  
permit 10.24.35.56  
permit 23.45.56.34  
Extended IP access list 120  
Extended MAC access list mac1  
This example shows only IP standard and extended ACLs.  
Switch# show ip access-lists  
Standard IP access list 1  
permit 172.20.10.10  
Standard IP access list 10  
permit 12.12.12.12  
Standard IP access list 12  
deny  
1.3.3.2  
Standard IP access list 32  
permit 172.20.20.20  
Standard IP access list 34  
permit 10.24.35.56  
permit 23.45.56.34  
Extended IP access list 120  
Displaying Access Groups  
You use the ip access-group interface configuration command to apply ACLs to a Layer 3 interface.  
When IP is enabled on an interface, you can use the show ip interface interface-id privileged EXEC  
command to view the input and output access lists on the interface, as well as other interface  
characteristics. If IP is not enabled on the interface, the access lists are not shown.  
This example shows how to view all access groups configured for VLAN 1:  
Switch# show ip interface vlan 1  
Vlan1 is up, line protocol is up  
Internet address is 10.20.30.1/16  
Broadcast address is 255.255.255.255  
Address determined by setup command  
MTU is 1500 bytes  
Helper address is not set  
Directed broadcast forwarding is disabled  
Outgoing access list is permit Any  
Inbound access list is 13  
<information truncated>  
This example shows how to view all access groups configured for an interface:  
Switch# show ip interface gigabitethernet0/17  
gigabitethernet0/17 is down, line protocol is down  
Inbound access list is ip1  
The only way to ensure that you can view all configured access groups under all circumstances is to use  
the show running-config privileged EXEC command. To display the ACL configuration of a single  
interface, use the show running-config interface interface-id command.  
This example shows how to display the ACL configuration of Gigabit Ethernet interface 0/17:  
Switch# show running-config interface gigabitethernet0/17  
Building configuration...  
Current configuration :112 bytes  
!
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Chapter 22 Configuring Network Security with ACLs  
Examples for Compiling ACLs  
interface GigabitEthernet0/17  
ip access-group 11 in  
snmp trap link-status  
no cdp enable  
end!  
Examples for Compiling ACLs  
For detailed information about compiling ACLs, see the Security Configuration Guide and the “IP  
Services” chapter of the Cisco IOS IP and IP Routing Configuration Guide, Cisco IOS Release 12.1.  
Figure 22-2 shows a small networked office with a number of switches that are connected to a Cisco  
router. A host is connected to the network through the Internet using a WAN link.  
Use switch ACLs to do these:  
•
•
Create a standard ACL, and filter traffic from a specific Internet host with an address 172.20.128.64.  
Create an extended ACL, and filter traffic to deny HTTP access to all Internet hosts but allow all  
other types of access.  
Figure 22-2  
Using Switch ACLs to Control Traffic  
Internet  
Workstation  
Cisco router  
BladeCenter  
BladeCenter  
BladeCenter  
This example uses a standard ACL to allow access to a specific Internet host with the address  
172.20.128.64.  
Switch(config)# access-list 6 permit 172.20.128.64 0.0.0.0  
Switch(config)# end  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# ip access-group 6 in  
This example uses an extended ACL to deny traffic from port 80 (HTTP). It permits all other types of  
traffic.  
Switch(config)# access-list 106 deny tcp any any eq 80  
Switch(config)# access-list 106 permit ip any any  
Switch(config)# interface gigabitethernet0/20  
Switch(config-if)# ip access-group 106 in  
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Chapter 22 Configuring Network Security with ACLs  
Examples for Compiling ACLs  
Numbered ACL Examples  
This example shows that the switch accepts addresses on network 36.0.0.0 subnets and denies all packets  
coming from 56.0.0.0 subnets. The ACL is then applied to packets entering an interface.  
Switch(config)# access-list 2 permit 36.0.0.0 0.255.255.255  
Switch(config)# access-list 2 deny 56.0.0.0 0.255.255.255  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# ip access-group 2 in  
Extended ACL Examples  
In this example of using an extended ACL, you have a network connected to the Internet, and you want  
any host on the network to be able to form TCP Telnet and SMTP connections to any host on the Internet.  
Switch(config)# access-list 102 permit tcp any 128.88.0.0 0.0.255.255 eq 23  
Switch(config)# access-list 102 permit tcp any 128.88.0.0 0.0.255.255 eq 25  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# ip access-group 102 in  
SMTP uses TCP port 25 on one end of the connection and a random port number on the other end. The  
same port numbers are used throughout the life of the connection. Mail packets coming in from the  
Internet have a destination port of 25. Because the secure system behind the switch always accepts mail  
connections on port 25, the incoming services are controlled.  
Named ACL Example  
The Marketing_group ACL allows any TCP Telnet traffic to the destination address and wildcard  
171.69.0.0 0.0.255.255 and denies any other TCP traffic. It permits any other IP traffic.  
Switch(config)# ip access-list extended marketing_group  
Switch(config-ext-nacl)# permit tcp any 171.69.0.0 0.0.255.255 eq telnet  
Switch(config-ext-nacl)# deny tcp any any  
Switch(config-ext-nacl)# permit ip any any  
The ACLs are applied to permit a port with the Marketing_group ACL applied to incoming traffic.  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# ip access-group marketing_group in  
...  
Commented IP ACL Entry Examples  
In this example of a numbered ACL, the workstation belonging to Jones is allowed access, and the  
workstation belonging to Smith is not allowed access:  
Switch(config)# access-list 1 remark Permit only Jones workstation through  
Switch(config)# access-list 1 permit 171.69.2.88  
Switch(config)# access-list 1 remark Do not allow Smith workstation through  
Switch(config)# access-list 1 deny 171.69.3.13  
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Chapter 22 Configuring Network Security with ACLs  
Examples for Compiling ACLs  
In this example of a numbered ACL, the Winter and Smith workstations are not allowed to browse the  
web:  
Switch(config)# access-list 100 remark Do not allow Winter to browse the web  
Switch(config)# access-list 100 deny host 171.69.3.85 any eq www  
Switch(config)# access-list 100 remark Do not allow Smith to browse the web  
Switch(config)# access-list 100 deny host 171.69.3.13 any eq www  
In this example of a named ACL, the Jones subnet is not allowed access:  
Switch(config)# ip access-list standard prevention  
Switch(config-std-nacl)# remark Do not allow Jones subnet through  
Switch(config-std-nacl)# deny 171.69.0.0 0.0.255.255  
In this example of a named ACL, the Jones subnet is not allowed to use outbound Telnet:  
Switch(config)# ip access-list extended telnetting  
Switch(config-ext-nacl)# remark Do not allow Jones subnet to telnet out  
Switch(config-ext-nacl)# deny tcp 171.69.0.0 0.0.255.255 any eq telnet  
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C H A P T E R  
23  
Configuring QoS  
This chapter describes how to configure quality of service (QoS) by using automatic-QoS (auto-QoS)  
commands or by using standard QoS commands. With QoS, you can give preferential treatment to  
certain types of traffic at the expense of others. Without QoS, the Cisco Systems Intelligent Gigabit  
Ethernet Switch Module offers best-effort service to each packet, regardless of the packet contents or  
size. It sends the packets without any assurance of reliability, delay bounds, or throughput.  
Table 23-1 lists the sections that describe the features that you can configure.  
Table 23-1  
Sections Describing Standard Software Features  
Topic  
Section  
Queueing and scheduling at the “Queueing and Scheduling” section on page 23-7  
egress ports  
Configuring QoS  
“Configuring Standard QoS” section on page 23-16  
“Default Standard QoS Configuration” section on page 23-16  
“Configuring Classification Using Port Trust States” section on  
page 23-17  
“Configuring the Egress Queues” section on page 23-34  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
The switch supports some of the modular QoS CLI (MQC) commands. For more information about the  
MQC commands, see the “Modular Quality of Service Command Line Interface Overview” at this URL:  
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_c/fqcprt8/qcfmdcli.htm#89799  
QoS can be configured either by using CiscoWorks or the command-line interface (CLI).  
This chapter consists of these sections:  
•
•
•
•
•
Understanding QoS, page 23-2  
Configuring Auto-QoS, page 23-9  
Displaying Auto-QoS Information, page 23-13  
Auto-QoS Configuration Example, page 23-14  
Configuring Standard QoS, page 23-16  
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Chapter 23 Configuring QoS  
Understanding QoS  
•
•
Displaying Standard QoS Information, page 23-36  
Standard QoS Configuration Examples, page 23-36  
Understanding QoS  
This section describes how QoS is implemented on the switch. For a list of available features, see  
Table 23-1 on page 23-1.  
Typically, networks operate on a best-effort delivery basis, which means that all traffic has equal priority  
and an equal chance of being delivered in a timely manner. When congestion occurs, all traffic has an  
equal chance of being dropped.  
When you configure the QoS feature, you can select specific network traffic, prioritize it according to  
its relative importance, and use congestion-management and congestion-avoidance techniques to give  
preferential treatment. Implementing QoS in your network makes network performance more  
predictable and bandwidth utilization more effective.  
The QoS implementation is based on the DiffServ architecture, an emerging standard from the Internet  
Engineering Task Force (IETF). This architecture specifies that each packet is classified upon entry into  
the network. The classification is carried in the IP packet header, using 6 bits from the deprecated IP  
type-of-service (ToS) field to carry the classification (class) information.  
Classification can also be carried in the Layer 2 frame. These special bits in the Layer 2 frame or  
a Layer 3 packet are described here and shown in Figure 23-1:  
•
Prioritization values in Layer 2 frames  
Layer 2 IEEE 802.1Q frame headers have a 2-byte Tag Control Information field that carries the  
class of service (CoS) value in the three most-significant bits, which are called the User Priority bits.  
On interfaces configured as Layer 2 IEEE 802.1Q trunks, all traffic is in IEEE 802.1Q frames except  
for traffic in the native VLAN.  
Other frame types cannot carry Layer 2 CoS values.  
Layer 2 CoS values range from 0 for low priority to 7 for high priority.  
Prioritization bits in Layer 3 packets  
•
Layer 3 IP packets can carry a Differentiated Services Code Point (DSCP) value. The supported  
DSCP values are 0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48, and 56.  
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Chapter 23 Configuring QoS  
Understanding QoS  
Figure 23-1  
QoS Classification Layers in Frames and Packets  
Encapsulated Packet  
Layer 2  
IP header  
Data  
header  
Layer 2 802.1Q and 802.1p Frame  
Start frame  
Preamble  
DA  
SA  
Tag  
PT Data FCS  
delimiter  
3 bits used for CoS (user priority)  
Layer 3 IPv4 Packet  
Version  
length  
ToS  
(1 byte)  
Len  
ID Offset TTL Proto FCS IP-SA IP-DA Data  
DSCP  
All switches and routers that access the Internet rely on the class information to give the same  
forwarding treatment to packets with the same class information and different treatment to packets with  
different class information. The class information in the packet can be assigned by end hosts or by  
switches or routers along the way, based on a configured policy, detailed examination of the packet, or  
both. Detailed examination of the packet is expected to happen closer to the edge of the network so that  
the core switches and routers are not overloaded.  
Switches and routers along the path can use the class information to limit the amount of resources  
allocated per traffic class. The behavior of an individual device when handling traffic in the DiffServ  
architecture is called per-hop behavior. If all devices along a path have a consistent per-hop behavior,  
you can construct an end-to-end QoS solution.  
Implementing QoS in your network can be a simple or complex task and depends on the QoS features  
offered by your internetworking devices, the traffic types and patterns in your network, and the  
granularity of control that you need over incoming and outgoing traffic.  
Basic QoS Model  
Figure 23-2 shows the basic QoS model. Actions at the ingress interface include classifying traffic,  
policing, and marking:  
•
Classifying distinguishes one kind of traffic from another. For more information, see the  
“Classification” section on page 23-4.  
•
Policing determines whether a packet is in or out of profile according to the configured policer, and  
the policer limits the bandwidth consumed by a flow of traffic. The result of this determination is  
passed to the marker. For more information, see the “Policing and Marking” section on page 23-6.  
•
Marking evaluates the policer and configuration information for the action to be taken when a packet  
is out of profile and decides what to do with the packet (pass through a packet without modification,  
mark down the DSCP value in the packet, or drop the packet). For more information, see the  
“Policing and Marking” section on page 23-6.  
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Chapter 23 Configuring QoS  
Understanding QoS  
Actions at the egress interface include queueing and scheduling:  
•
Queueing evaluates the CoS value and determines which of the four egress queues in which to place  
the packet.  
•
Scheduling services the four egress queues based on their configured weighted round robin (WRR)  
weights.  
Figure 23-2  
Basic QoS Model  
Actions at ingress  
Actions at egress  
In profile or  
out of profile  
Queuing and  
scheduling  
Classification  
Policing  
Mark  
Classifies the packet  
based on the ACL.  
Determines if the  
Based on whether  
the packet is in or  
out of profile and the  
configured  
Based on the CoS,  
determines into  
which of the egress  
queues to place the  
packet, then  
services the queues  
according to the  
configured weights.  
packet is in profile or  
out of profile based  
on the policer  
associated with the  
filter.  
parameters,  
determines whether  
to pass through,  
mark down, or drop  
the packet. The  
DSCP and CoS are  
marked or changed  
accordingly.  
Classification  
Classification is the process of distinguishing one kind of traffic from another by examining the fields  
in the packet.  
Classification occurs only on a physical interface basis. No support exists for classifying packets at the  
VLAN level.  
You specify which fields in the frame or packet that you want to use to classify incoming traffic.  
For non-IP traffic, you have these classification options:  
•
Use the port default. If the frame does not contain a CoS value, the switch assigns the default port  
CoS value to the incoming frame.  
•
Trust the CoS value in the incoming frame (configure the port to trust CoS). Layer 2 IEEE 802.1Q  
frame headers carry the CoS value in the three most-significant bits of the Tag Control Information  
field. CoS values range from 0 for low priority to 7 for high priority.  
The trust DSCP configuration is meaningless for non-IP traffic. If you configure a port with this  
option and non-IP traffic is received, the switch assigns the default port CoS value and classifies  
traffic based on the CoS value.  
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Chapter 23 Configuring QoS  
Understanding QoS  
For IP traffic, you have these classification options:  
•
Trust the IP DSCP in the incoming packet (configure the port to trust DSCP). The switch assigns the  
same DSCP to the packet for internal use. The IETF defines the 6 most-significant bits of the 1-byte  
ToS field as the DSCP. The priority represented by a particular DSCP value is configurable. The  
supported DSCP values are 0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48, and 56.  
•
Trust the CoS value (if present) in the incoming packet. The switch generates the DSCP by using the  
CoS-to-DSCP map.  
Note  
An interface can be configured to trust either CoS or DSCP, but not both at the same time.  
Classification Based on QoS ACLs  
You can use IP standard, IP extended, and Layer 2 MAC access control lists (ACLs) to define a group  
of packets with the same characteristics (class). In the QoS context, the permit and deny actions in the  
access control entries (ACEs) have different meanings than with security ACLs:  
•
•
•
If a match with a permit action is encountered (first-match principle), the specified QoS-related  
action is taken.  
If no match with a permit action is encountered and all the ACEs have been examined, no QoS  
processing occurs on the packet.  
If multiple ACLs are configured on an interface, the packet matches the first ACL with a permit  
action, and QoS processing begins.  
•
•
Configuration of a deny action is not supported in QoS ACLs on the switch.  
System-defined masks are allowed in class maps with these restrictions:  
–
A combination of system-defined and user-defined masks cannot be used in the multiple class  
maps that are a part of a policy map.  
–
System-defined masks that are a part of a policy map must all use the same type of system mask.  
For example, a policy map cannot have a class map that uses the permit tcp any any ACE and  
another that uses the permit ip any any ACE.  
–
A policy map can contain multiple class maps that all use the same user-defined mask or the  
same system-defined mask.  
Note  
For more information about system-defined masks, see the “Understanding Access Control Parameters”  
section on page 22-4.  
For more information about ACL restrictions, see the “Configuring ACLs” section on page 22-6.  
After a traffic class has been defined with the ACL, you can attach a policy to it. A policy might contain  
multiple classes with actions specified for each one of them. A policy might include commands to  
classify the class as a particular aggregate (for example, assign a DSCP) or rate-limit the class. This  
policy is then attached to a particular port on which it becomes effective.  
You implement IP ACLs to classify IP traffic by using the access-list global configuration command;  
you implement Layer 2 MAC ACLs to classify Layer 2 traffic by using the mac access-list extended  
global configuration command.  
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Chapter 23 Configuring QoS  
Understanding QoS  
Classification Based on Class Maps and Policy Maps  
A class map is a mechanism that you use to isolate and name a specific traffic flow (or class) from all  
other traffic. The class map defines the criteria used to match against a specific traffic flow to further  
classify it; the criteria can include matching the access group defined by the ACL. If you have more than  
one type of traffic that you want to classify, you can create another class map and use a different name.  
After a packet is matched against the class-map criteria, you further classify it through the use of a policy  
map.  
A policy map specifies which traffic class to act on. Actions can include setting a specific DSCP value  
in the traffic class or specifying the traffic bandwidth limitations and the action to take when the traffic  
is out of profile. Before a policy map can be effective, you must attach it to an interface.  
You create a class map by using the class-map global configuration command or the class policy-map  
configuration command. You should use the class-map global configuration command when the map is  
shared among many ports. When you enter the class-map global configuration command, the switch  
enters the class-map configuration mode. In this mode, you define the match criterion for the traffic by  
using the match class-map configuration command.  
You create and name a policy map by using the policy-map global configuration command. When you  
enter this command, the switch enters the policy-map configuration mode. In this mode, you specify the  
actions to take on a specific traffic class by using the class policy-map configuration or set policy-map  
class configuration command. To make the policy map effective, you attach it to an interface by using  
the service-policy interface configuration command.  
The policy map can also contain commands that define the policer, the bandwidth limitations of the  
traffic, and the action to take if the limits are exceeded. For more information, see the “Policing and  
Marking” section on page 23-6.  
A policy map also has these characteristics:  
•
•
•
A policy map can contain multiple class statements.  
A separate policy-map class can exist for each type of traffic received through an interface.  
A policy-map configuration state supersedes any actions due to an interface trust state.  
For configuration information, see the “Configuring a QoS Policy” section on page 23-23.  
Policing and Marking  
Policing involves creating a policer that specifies the bandwidth limits for the traffic. Packets that exceed  
the limits are out of profile or nonconforming. Each policer specifies the action to take for packets that  
are in or out of profile. These actions, carried out by the marker, include dropping the packet or marking  
down the packet with a new user-defined value.  
You can create an individual policer. QoS applies the bandwidth limits specified in the policer separately  
to each matched traffic class. You configure this type of policer within a policy map by using the  
policy-map configuration command.  
When configuring policing and policers, keep these items in mind:  
•
•
•
•
•
By default, no policers are configured.  
Policers can only be configured on a physical port. There is no support for policing at a VLAN level.  
Only one policer can be applied to a packet in the input direction.  
Only the average rate and committed burst parameters are configurable.  
Policing occurs on the ingress interfaces:  
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Chapter 23 Configuring QoS  
Understanding QoS  
–
–
60 policers are supported on ingress Gigabit-capable Ethernet ports.  
Granularity for the average burst rate is 8 Mbps for Gigabit Ethernet ports.  
•
On an interface configured for QoS, all traffic received through the interface is classified, policed,  
and marked according to the policy map attached to the interface. On a trunk interface configured  
for QoS, traffic in all VLANs received through the interface is classified, policed, and marked  
according to the policy map attached to the interface.  
Note  
You cannot configure policers on the egress interfaces.  
Mapping Tables  
During classification, QoS uses a configurable CoS-to-DSCP map to derive an internal DSCP value from  
the received CoS value. This DSCP value represents the priority of the traffic.  
Before the traffic reaches the scheduling stage, QoS uses the configurable DSCP-to-CoS map to derive  
a CoS value from the internal DSCP value. The CoS value is used to select one of the four egress queues.  
The CoS-to-DSCP and DSCP-to-CoS maps have default values that might or might not be appropriate  
for your network.  
For configuration information, see the “Configuring CoS Maps” section on page 23-31.  
Queueing and Scheduling  
The switch gives QoS-based IEEE 802.1p CoS values. QoS uses classification and scheduling to send  
network traffic from the switch in a predictable manner. QoS classifies frames by assigning  
priority-indexed CoS values to them and gives preference to higher-priority traffic such as telephone  
calls.  
How Class of Service Works  
Before you set up IEEE 802.1p CoS on a Cisco Systems Intelligent Gigabit Ethernet Switch Module that  
operates with the Catalyst 6000 family of switches, see the Catalyst 6000 documentation. There are  
differences in the IEEE 802.1p implementation that you should understand to ensure compatibility.  
Port Priority  
Frames received from users in the administratively defined VLANs are classified or tagged for  
transmission to other devices. Based on rules that you define, a unique identifier (the tag) is inserted in  
each frame header before it is forwarded. The tag is examined and understood by each device before any  
broadcasts or transmissions to other switches, routers, or end stations. When the frame reaches the last  
switch or router, the tag is removed before the frame is sent to the target end station. VLANs that are  
assigned on trunk or access ports without identification or a tag are called native or untagged frames.  
For IEEE 802.1Q frames with tag information, the priority value from the header frame is used. For  
native frames, the default priority of the input port is used.  
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Chapter 23 Configuring QoS  
Understanding QoS  
Port Scheduling  
Each port on the switch has a single receive queue buffer (the ingress port) for incoming traffic. When  
an untagged frame arrives, it is assigned the value of the port as its port default priority. You assign this  
value by using the CLI or CiscoWorks. A tagged frame continues to use its assigned CoS value when it  
passes through the ingress port.  
CoS configures each transmit port (the egress port) with a normal-priority transmit queue and a  
high-priority transmit queue, depending on the frame tag or the port information. Frames in the  
normal-priority queue are forwarded only after frames in the high-priority queue are forwarded.  
The switch (IEEE 802.1P user priority) has four priority queues. The frames are forwarded to  
appropriate queues based on the priority-to-queue mapping that you defined.  
Egress CoS Queues  
The switch supports four CoS queues for each egress port. For each queue, you can specify these types  
of scheduling:  
•
Strict priority scheduling  
Strict priority scheduling is based on the priority of queues. Packets in the high-priority queue are  
always sent first, and packets in the low-priority queue are not sent until all the high-priority queues  
become empty.  
The default scheduling method is strict priority.  
Weighted round-robin (WRR) scheduling  
•
WRR scheduling requires you to specify a number that indicates the importance (weight) of the  
queue relative to the other CoS queues. WRR scheduling prevents the low-priority queues from  
being completely neglected during periods of high-priority traffic. The WRR scheduler sends some  
packets from each queue in turn. The number of packets it sends corresponds to the relative  
importance of the queue. For example, if one queue has a weight of 3 and another has a weight of 4,  
three packets are sent from the first queue for every four that are sent from the second queue. By  
using this scheduling, low-priority queues have the opportunity to send packets even though the  
high-priority queues are not empty.  
•
Strict priority and WRR scheduling  
Strict priority and WRR scheduling, also referred to as strict priority queueing, uses one of the  
egress queues as an expedite queue (queue 4). The remaining queues participate in WRR. When the  
expedite queue is configured, it is a priority queue and is serviced until it is empty before the other  
queues are serviced by WRR scheduling.  
You can enable the egress expedite queue and assign WRR weights to the other queues by using the  
wrr-queue bandwidth weight1 weight2 weight3 0 global configuration command.  
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Chapter 23 Configuring QoS  
Configuring Auto-QoS  
Configuring Auto-QoS  
You can use the auto-QoS feature to simplify the deployment of existing QoS features. Auto-QoS makes  
assumptions about the network design, and as a result, the switch can prioritize different traffic flows  
and appropriately use the egress queues instead of using the default QoS behavior (the switch offers  
best-effort service to each packet regardless of the packet contents or size and sends it from a single  
queue).  
When you enable auto-QoS, it automatically classifies traffic based on the traffic type and ingress packet  
label. The switch uses the resulting classification to choose the appropriate egress queue.  
You use auto-QoS commands to identify ports connected to Cisco IP Phones. You also use the  
commands to identify ports that receive trusted traffic through an uplink. Auto-QoS then performs these  
functions:  
•
•
•
Detects the presence or absence of IP phones  
Configures QoS classification  
Configures egress queues  
These sections describe how to configure auto-QoS on your switch:  
•
•
•
•
Generated Auto-QoS Configuration, page 23-9  
Effects of Auto-QoS on the Configuration, page 23-11  
Configuration Guidelines, page 23-11  
Enabling Auto-QoS for VoIP, page 23-12  
Generated Auto-QoS Configuration  
When auto-QoS is enabled, it uses the ingress packet label to classify traffic and to configure the egress  
queues as described in Table 23-2.  
Table 23-2  
Traffic Types, Packet Labels, and Egress Queues  
VoIP1 Data VoIP Control Routing Protocol STP BPDU2 Real-Time  
Traffic  
Traffic  
24, 26  
3
Traffic  
Traffic  
Video Traffic  
All Other Traffic  
DSCP  
CoS  
46  
5
48  
6
56  
7
34  
4
–
CoS-to-Queue  
Map  
5
3, 6, 7  
4
2
0, 1  
Egress Queue  
1% WRR  
(queue 4)  
70% WRR (queue 3)  
20% WRR  
(queue 2)  
20% WRR  
(queue 2)  
10% WRR  
(queue 1)  
1. VoIP = voice over IP  
2. BPDU = bridge protocol data unit  
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Chapter 23 Configuring QoS  
Configuring Auto-QoS  
Table 23-3 lists the generated auto-QoS configuration for the egress queues.  
Table 23-3  
Auto-QoS Configuration for the Egress Queues  
Egress Queue  
1% WRR  
Queue Number  
CoS-to-Queue Map  
Queue Weight  
1 percent  
4
3
2
1
5
70% WRR  
20% WRR  
10% WRR  
3, 6, 7  
2, 4  
0,1  
70 percent  
20 percent  
10 percent  
When you enable the auto-QoS feature on the first interface, these automatic actions occur:  
•
When you enter the auto qos voip cisco-phone interface configuration command on a port at the  
edge of a network that is connected to a Cisco IP Phone, the switch enables the trusted boundary  
feature. The switch uses the Cisco Discovery Protocol (CDP) to detect the presence or absence of a  
Cisco IP Phone. When a Cisco IP Phone is detected, the ingress classification on the interface is set  
to trust the QoS label received in the packet. When a Cisco IP Phone is absent, the ingress  
classification is set to not trust the QoS label in the packet. The switch configures egress queues on  
the port according to the settings in Table 23-3.  
•
When you enter the auto qos voip trust interface configuration command on a port connected to  
the interior of the network, the switch trusts the CoS value in ingress packets (the assumption is that  
traffic has already been classified by other edge devices). The switch configures egress queues on  
the port according to the settings in Table 23-3.  
For information about the trusted boundary feature, see the “Configuring Trusted Boundary” section  
on page 23-20.  
When you enable auto-QoS by using the auto qos voip cisco-phone or the auto qos voip trust interface  
configuration command, the switch automatically generates a QoS configuration based on the traffic  
type and ingress packet label and applies the commands listed in Table 23-4 to the interface.  
Table 23-4  
Generated Auto-QoS Configuration  
Description  
Automatically Generated QoS Command Equivalent  
Switch(config)# mls qos map cos-dscp 0 8 16 26 32 46  
48 56  
The switch automatically enables standard QoS and configures  
the CoS-to-DSCP map (maps CoS values in incoming packets  
to a DSCP value) as shown in Table 23-2 on page 23-9.  
Switch(config-if)# mls qos trust cos  
If you entered the auto qos voip trust command, the switch  
automatically sets the ingress classification on the interface to  
trust the CoS value in the packet.  
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Chapter 23 Configuring QoS  
Configuring Auto-QoS  
Table 23-4  
Generated Auto-QoS Configuration (continued)  
Automatically Generated QoS Command Equivalent  
Description  
Switch(config-if)# mls qos trust device cisco-phone  
If you entered the auto qos voip cisco-phone command, the  
switch automatically enables the trusted boundary feature,  
which uses the CDP to detect the presence or the absence of a  
Cisco IP Phone.  
Switch(config)# wrr-queue bandwidth 10 20 70 1  
Switch(config)# no wrr-queue cos-map  
Switch(config)# wrr-queue cos-map 1 0 1  
Switch(config)# wrr-queue cos-map 2 2 4  
Switch(config)# wrr-queue cos-map 3 3 6 7  
Switch(config)# wrr-queue cos-map 4 5  
The switch automatically assigns the egress queue usage (as  
shown in Table 23-3 on page 23-10) on this interface.  
If some of your network traffic requires expedited forwarding,  
configure queue 4 as the expedite queue. When the WRR  
weight of a queue is set to 0, this queue becomes an expedite  
queue. Only queue 4 can be the expedite queue.  
The switch configures the CoS-to-egress-queue map:  
•
•
•
•
CoS values 0 and 1 select queue 1.  
CoS values 2 and 4 select queue 2.  
CoS values 3, 6, and 7 select queue 3.  
CoS value 5 selects queue 4.  
Effects of Auto-QoS on the Configuration  
When auto-QoS is enabled, the auto qos voip interface configuration command and the generated  
configuration are added to the running configuration.  
The switch applies the auto-QoS-generated commands as if the commands were entered from the CLI.  
An existing user configuration can cause the application of the generated commands to fail or to be  
overridden by the generated commands. These actions occur without warning. If all the generated  
commands are successfully applied, any user-entered configuration that was not overridden remains in  
the running configuration. Any user-entered configuration that was overridden can be retrieved by  
reloading the switch without saving the current configuration to memory. If the generated commands  
fail to be applied, the previous running configuration is restored.  
Configuration Guidelines  
Before configuring auto-QoS, you should be aware of this information:  
•
•
•
To take advantage of the auto-QoS defaults, you should enable auto-QoS before you configure other  
QoS commands. If necessary, you can fine-tune the QoS configuration, but we recommend that you  
do so only after the auto-QoS configuration is completed. For more information, see the “Effects of  
Auto-QoS on the Configuration” section on page 23-11.  
After auto-QoS is enabled, do not modify a policy map or aggregate policer that includes AutoQoS  
in its name. If you need to modify the policy map or aggregate policer, make a copy of it, and change  
the copied policy map or policer. To use the new policy map instead of the generated one, remove  
the generated policy map from the interface, and apply the new policy map to it.  
You can enable auto-QoS on static, dynamic-access, voice VLAN access, and trunk ports.  
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Configuring Auto-QoS  
•
•
By default, the CDP is enabled on all interfaces. For auto-QoS to function properly, do not disable  
the CDP.  
Connected devices must use Cisco Call Manager Version 4 or later.  
Enabling Auto-QoS for VoIP  
Beginning in privileged EXEC mode, follow these steps to enable auto-QoS for VoIP within a QoS  
domain:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface that is connected to a Cisco IP Phone, and enter  
interface configuration mode. You also can specify the uplink interface  
that is connected to another trusted witch or router in the interior of the  
network.  
Step 3  
auto qos voip {cisco-phone | trust}  
Enable auto-QoS.  
The keywords have these meanings:  
•
cisco-phone—If the interface is connected to a Cisco IP Phone,  
the QoS labels of incoming packets are trusted only when the IP  
phone is detected.  
•
trust—The uplink interface is connected to a trusted switch or  
router, and the VoIP classification in the ingress packet is trusted.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show auto qos interface interface-id  
This command displays the auto-QoS command on the interface on  
which auto-QoS was enabled. You can use the show running-config  
privileged EXEC command to display the auto-QoS configuration and  
the user modifications.  
To disable auto-QoS on the switch and return to the default port trust state set (untrusted), follow these  
steps:  
1. Use the no auto qos voip interface configuration command on all interfaces on which auto-QoS is  
enabled. To disable auto-QoS on multiple interfaces at the same time, you can use the interface  
range global configuration command.  
2. After disabling auto-QoS on all interfaces on which auto-QoS was enabled, return the egress queues  
and CoS-to-DSCP map to the default settings by using these global configuration commands:  
•
•
•
no wrr-queue bandwidth  
no wrr-queue cos-map  
no mls qos map cos-dscp  
To display the QoS commands that are automatically generated when auto-QoS is enabled or disabled,  
enter the debug auto qos privileged EXEC command before enabling auto-QoS. For more information,  
see the “Using the debug auto qos Command” section on page 25-12.  
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Chapter 23 Configuring QoS  
Displaying Auto-QoS Information  
This example shows how to enable auto-QoS and to trust the QoS labels in incoming packets when the  
device connected to the interface is detected as a Cisco IP Phone:  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# auto qos voip cisco-phone  
This example shows how to enable auto-QoS and to trust the QoS labels in incoming packets when the  
switch or router connected to the interface is a trusted device:  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# auto qos voip trust  
Displaying Auto-QoS Information  
To display the initial auto-QoS configuration, use the show auto qos [interface [interface-id]]  
privileged EXEC command. To display any user changes to that configuration, use the show  
running-config privileged EXEC command. You can compare the show auto qos and the show  
running-config command output to identify the user-defined QoS settings.  
To display information about the QoS configuration that might be affected by auto-QoS, use one of these  
commands:  
•
•
•
•
show mls qos  
show mls qos map cos-dscp  
show wrr-queue bandwidth  
show wrr-queue cos-map  
For more information about these commands, see the command reference for this release.  
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Chapter 23 Configuring QoS  
Auto-QoS Configuration Example  
Auto-QoS Configuration Example  
This section describes how you could implement auto-QoS in a network, as shown in Figure 23-3. For  
optimum QoS performance, auto-QoS should be enabled on all the devices in the network.  
Figure 23-3  
Auto-QoS Configuration Example Network  
Cisco router  
To Internet  
Trunk  
link  
Trunk  
link  
Video server  
172.20.10.16  
End stations  
Identify this interface  
as connected to a  
trusted switch or router  
Identify this interface  
as connected to a  
trusted switch or router  
IP  
IP  
Identify these  
Identify these  
interfaces as  
connected to  
IP phones  
interfaces as  
connected to  
IP phones  
IP  
IP  
Cisco IP phones  
Cisco IP phones  
The intelligent wiring closets in Figure 23-3 are composed of Catalyst 2950 switches running the EI and  
Catalyst 3550 switches. The object of this example is to prioritize the VoIP traffic over all other traffic.  
To do so, enable auto-QoS on the switches at the edge of the QoS domains in the wiring closets.  
Note  
You should not configure any standard-QoS commands before entering the auto-QoS commands. You  
can fine-tune the QoS configuration, but we recommend that you do so only after the auto-QoS  
configuration is completed.  
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Chapter 23 Configuring QoS  
Auto-QoS Configuration Example  
Beginning in privileged EXEC mode, follow these steps to configure the switch at the edge of the QoS  
domain to prioritize the VoIP traffic over all other traffic:  
Command  
Purpose  
Step 1  
debug auto qos  
Enable debugging for auto-QoS. When debugging is enabled, the switch  
displays the QoS configuration that is automatically generated when auto-QoS  
is enabled.  
Step 2  
Step 3  
Step 4  
configure terminal  
cdp enable  
Enter global configuration mode.  
Enable CDP globally. By default, it is enabled.  
interface interface-id  
Specify the switch port connected to the Cisco IP Phone, and enter interface  
configuration mode.  
Step 5  
auto qos voip cisco-phone  
Enable auto-QoS on the interface, and specify that the interface is connected to  
a Cisco IP Phone.  
The QoS labels of incoming packets are trusted only when the IP phone is  
detected.  
Step 6  
Step 7  
Step 8  
exit  
Return to global configuration mode.  
Repeat Steps 4 to 6 for as many ports as are connected to the Cisco IP Phone.  
interface interface-id  
Specify the switch port identified as connected to a trusted switch or router, and  
enter interface configuration mode. See Figure 23-3.  
Step 9  
auto qos voip trust  
Enable auto-QoS on the interface, and specify that the interface is connected to  
a trusted router or switch.  
Step 10  
Step 11  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show auto qos  
This command displays the auto-QoS command on the interface on which  
auto-QoS was enabled. You can use the show running-config privileged EXEC  
command to display the auto-QoS configuration and the user modifications.  
For information about the QoS configuration that might be affected by  
auto-QoS, see the “Displaying Auto-QoS Information” section on page 26-12.  
Step 12  
copy running-config  
startup-config  
Save the auto qos voip interface configuration commands and the generated  
auto-QoS configuration in the configuration file.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Configuring Standard QoS  
Before configuring standard QoS, you must have a thorough understanding of these items:  
•
•
The types of applications used and the traffic patterns on your network.  
Traffic characteristics and needs of your network. Is the traffic bursty? Do you need to reserve  
bandwidth for voice and video streams?  
•
•
Bandwidth requirements and speed of the network.  
Location of congestion points in the network.  
This section describes how to configure standard QoS on your switch:  
•
•
•
•
•
•
Default Standard QoS Configuration, page 23-16  
Configuration Guidelines, page 23-16  
Configuring Classification Using Port Trust States, page 23-17  
Configuring a QoS Policy, page 23-23  
Configuring CoS Maps, page 23-31  
Configuring the Egress Queues, page 23-34  
Default Standard QoS Configuration  
This is the default standard QoS configuration:  
The default port CoS value is 0.  
The CoS value of 0 is assigned to all incoming packets.  
•
•
•
•
•
•
•
•
•
The default port trust state is untrusted.  
No policy maps are configured.  
No policers are configured.  
The default CoS-to-DSCP map is shown in Table 23-7.  
The default DSCP-to-CoS map is shown in Table 23-8.  
The default scheduling method for the egress queues is strict priority.  
For default CoS and WRR values, see the “Configuring the Egress Queues” section on page 23-34.  
Configuration Guidelines  
Before beginning the QoS configuration, you should be aware of this information:  
•
•
•
You must disable the IEEE 802.3x flowcontrol on all ports before enabling QoS on the switch. To  
disable it, use the flowcontrol receive off and flowcontrol send off interface configuration  
commands.  
If you have EtherChannel ports configured on your switch, you must configure QoS classification,  
policing, mapping, and queueing on the individual physical ports that comprise the EtherChannel.  
You must decide whether the QoS configuration should match on all ports in the EtherChannel.  
It is not possible to match IP fragments against configured IP extended ACLs to enforce QoS. IP  
fragments are sent as best-effort traffic. IP fragments are denoted by fields in the IP header.  
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Configuring Standard QoS  
•
All ingress QoS processing actions apply to control traffic (such as spanning-tree bridge protocol  
data units [BPDUs] and routing update packets) that the switch receives.  
•
•
Only an ACL that is created for physical interfaces can be attached to a class map.  
Only one ACL per class map and only one match command per class map are supported. The ACL  
can have multiple access control entries, which are commands that match fields against the contents  
of the packet.  
•
Policy maps with ACL classification in the egress direction are not supported and cannot be attached  
to an interface by using the service-policy input policy-map-name interface configuration  
command.  
•
•
•
•
In a policy map, the class named class-default is not supported. The switch does not filter traffic  
based on the policy map defined by the class class-default policy-map configuration command.  
For more information about guidelines for configuring ACLs, see the “Classification Based on QoS  
ACLs” section on page 23-5.  
For information about applying ACLs to physical interfaces, see the “Guidelines for Applying ACLs  
to Physical Interfaces” section on page 22-5.  
If a policy map with a system-defined mask and a security ACL with a user-defined mask are  
configured on an interface, the switch might ignore the actions specified by the policy map and  
perform only the actions specified by the ACL. For information about masks, see the  
“Understanding Access Control Parameters” section on page 22-4.  
•
If a policy map with a user-defined mask and a security ACL with a user-defined mask are  
configured on an interface, the switch takes one of the actions as described in Table 23-5. For  
information about masks, see the “Understanding Access Control Parameters” section on page 22-4.  
Table 23-5  
Interaction Between Policy Maps and Security ACLs  
Security-ACL  
Conditions  
Policy-Map Conditions  
When the packet is in profile.  
Action  
Permit specified  
packets.  
Traffic is forwarded.  
When the packet is out of profile and the  
out-of-profile action is to mark down the DSCP  
value.  
Drop specified  
packets.  
Traffic is dropped.  
When the packet is out of profile and the  
out-of-profile action is to drop the packet.  
Permit specified  
packets.  
Traffic is dropped.  
Traffic is dropped.  
Drop specified  
packets.  
Configuring Classification Using Port Trust States  
This section describes how to classify incoming traffic by using port trust states:  
•
•
•
•
Configuring the Trust State on Ports within the QoS Domain, page 23-18  
Configuring the CoS Value for an Interface, page 23-19  
Configuring Trusted Boundary, page 23-20  
Enabling Pass-Through Mode, page 23-22  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Configuring the Trust State on Ports within the QoS Domain  
Packets entering a QoS domain are classified at the edge of the QoS domain. When the packets are  
classified at the edge, the switch port within the QoS domain can be configured to one of the trusted  
states because there is no need to classify the packets at every switch within the QoS domain. Figure 23-4  
shows a sample network topology.  
Figure 23-4  
Port Trusted States within the QoS Domain  
Catalyst  
3550-12T switch  
Trusted interface  
Trunk  
Catalyst 2950  
wiring closet  
BladeCenter  
Classification  
of traffic  
performed here  
IP  
Beginning in privileged EXEC mode, follow these steps to configure the port to trust the classification  
of the traffic that it receives:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to be trusted, and enter interface configuration  
mode.  
Valid interfaces include physical interfaces.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Command  
Purpose  
Step 3  
mls qos trust [cos | dscp]  
Configure the port trust state.  
By default, the port is not trusted.  
The keywords have these meanings:  
cos—Classifies ingress packets with the packet CoS values. For  
tagged IP packets, the DSCP value of the packet is modified based  
on the CoS-to-DSCP map. The egress queue assigned to the packet  
is based on the packet CoS value.  
dscp—Classifies ingress packets with packet DSCP values. For  
non-IP packets, the packet CoS value is set to 0 for tagged packets;  
the default port CoS is used for untagged packets. Internally, the  
switch modifies the CoS value by using the DSCP-to-CoS map.  
Use the cos keyword if your network is composed of Ethernet LANs.  
Use the dscp keyword if your network is not composed of only  
Ethernet LANs and if you are familiar with sophisticated QoS  
features and implementations.  
For more information about this command, see the command  
reference for this release.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show mls qos interface [interface-id]  
[policers]  
Step 6  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return a port to its untrusted state, use the no mls qos trust interface configuration command.  
For information on how to change the default CoS value, see the “Configuring the CoS Value for an  
Interface” section on page 23-19. For information on how to configure the CoS-to-DSCP map, see the  
“Configuring the CoS-to-DSCP Map” section on page 23-32.  
Configuring the CoS Value for an Interface  
QoS assigns the CoS value specified with the mls qos cos interface configuration command to untagged  
frames received on trusted and untrusted ports.  
Beginning in privileged EXEC mode, follow these steps to define the default CoS value of a port or to  
assign the default CoS to all incoming packets on the port:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface to be trusted, and enter interface configuration mode.  
Valid interfaces include physical interfaces.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Command  
Purpose  
Step 3  
mls qos cos {default-cos | override} Configure the default CoS value for the port.  
•
For default-cos, specify a default CoS value to be assigned to a port. If  
the port is CoS trusted and packets are untagged, the default CoS value  
becomes the CoS value for the packet. The CoS range is 0 to 7. The  
default is 0.  
•
Use the override keyword to override the previously configured trust  
state of the incoming packets and to apply the default port CoS value to  
all incoming packets. By default, CoS override is disabled.  
Use the override keyword when all incoming packets on certain ports  
deserve higher priority than packets entering from other ports. Even if  
a port was previously set to trust DSCP, this command overrides the  
previously configured trust state, and all the incoming CoS values are  
assigned the default CoS value configured with this command. If an  
incoming packet is tagged, the CoS value of the packet is modified with  
the default CoS of the port at the egress port.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show mls qos interface  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To return to the default setting, use the no mls qos cos {default-cos | override} interface configuration  
command.  
Configuring Trusted Boundary  
In a typical network, you connect a Cisco IP Phone to a switch port as shown in Figure 23-4 on  
page 23-18, and cascade devices that generate data packets from the back of the telephone. The Cisco IP  
Phone guarantees the voice quality through a shared data link by marking the CoS level of the voice  
packets as high priority (CoS = 5) and by marking the data packets as low priority (CoS = 0). Traffic  
sent from the telephone to the switch is typically marked with a tag that uses the IEEE 802.1Q header.  
The header contains the VLAN information and the class of service (CoS) 3-bit field, which is the  
priority of the packet.  
For most Cisco IP Phone configurations, the traffic sent from the telephone to the switch should be  
trusted to ensure that voice traffic is properly prioritized over other types of traffic in the network. By  
using the mls qos trust cos interface configuration command, you configure the switch port to which  
the telephone is connected to trust the CoS labels of all traffic received on that port.  
With the trusted setting, you also can use the trusted boundary feature to prevent misuse of a  
high-priority queue if a user bypasses the telephone and connects the PC directly to the switch. Without  
trusted boundary, the CoS labels generated by the PC are trusted by the switch (because of the trusted  
CoS setting). By contrast, trusted boundary uses CDP to detect the presence of a Cisco IP Phone (such  
as the Cisco IP Phone 7910, 7935, 7940, and 7960) on a switch port. If the telephone is not detected, the  
trusted boundary feature disables the trusted setting on the switch port and prevents misuse of a  
high-priority queue. Note that the trusted boundary feature is not effective if the PC and Cisco IP Phone  
are connected to a hub that is connected to the switch.  
In some situations, you can prevent a PC connected to the Cisco IP Phone from taking advantage of a  
high-priority data queue. You can use the switchport priority extend cos interface configuration  
command to configure the telephone through the switch CLI to override the priority of the traffic  
received from the PC.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Beginning in privileged EXEC mode, follow these steps to configure trusted boundary on a switch port:  
Command  
Purpose  
Step 1  
Step 2  
Step 3  
configure terminal  
cdp enable  
Enter global configuration mode.  
Enable CDP globally. By default, it is enabled.  
interface interface-id  
Specify the interface to be trusted, and enter interface configuration  
mode.  
Valid interfaces include physical interfaces.  
Step 4  
Step 5  
cdp enable  
Enable CDP on the interface. By default, CDP is enabled.  
Configure the Cisco IP Phone as a trusted device on the interface.  
mls qos trust device cisco-phone  
You cannot enable both trusted boundary and auto-QoS (auto qos  
voip interface configuration command) at the same time; they are  
mutually exclusive.  
Step 6  
mls qos trust cos  
Configure the port trust state to trust the CoS value of the ingress  
packet.  
By default, the port is not trusted.  
For more information on this command, see the command reference  
for this release.  
Step 7  
Step 8  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show mls qos interface [interface-id]  
[policers]  
Step 9  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
When you enter the no mls qos trust interface configuration command, trusted boundary is not disabled.  
If this command is entered and the port is connected to a Cisco IP Phone, the port does not trust the  
classification of traffic that it receives. To disable trusted boundary, use the no mls qos trust device  
interface configuration command  
If you enter the mls qos cos override interface configuration command, the port does not trust the  
classification of the traffic that it receives, even when it is connected to a Cisco IP Phone.  
You cannot enable trusted boundary if auto-QoS is already enabled and vice-versa. If auto-QoS is  
enabled and a Cisco IP Phone is absent on a port, the port does not trust the classification of traffic that  
it receives.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Table 23-6 lists the port configuration when an IP phone is present or absent.  
Table 23-6 Port Configurations When Trusted Boundary is Enabled  
Port Configuration When a Cisco IP Phone is Present When a Cisco IP Phone is Absent  
The port trusts the CoS value The packet CoS value is trusted.  
of the incoming packet.  
The packet CoS value is assigned  
the default CoS value.  
The port trusts the DSCP  
value of the incoming packet.  
The packet DSCP value is trusted. For tagged non-IP packets, the  
packet CoS value is set to 0.  
For untagged non-IP packets, the  
packet CoS value is assigned the  
default CoS value.  
The port assigns the default  
CoS value to incoming  
packets.  
The packet CoS value is assigned The packet CoS value is assigned  
the default CoS value.  
the default CoS value.  
Enabling Pass-Through Mode  
The switch assigns a CoS value of 0 to all incoming packets without modifying the packets. The switch  
offers best-effort service to each packet regardless of the packet contents or size and sends it from a  
single egress queue.  
Beginning in privileged EXEC mode, follow these steps to enable pass-through mode:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface on which pass-through mode is enabled, and enter  
interface configuration mode.  
Valid interfaces include physical interfaces.  
Step 3  
mls qos trust cos pass-through dscp Enable pass-through mode. The interface is configured to trust the CoS  
value of the incoming packets and to send them without modifying the  
DSCP value.  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
show mls qos interface [interface-id] Verify your entries.  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
To disable pass-through mode, use the no mls qos trust pass-through dscp interface configuration  
command.  
If you enter the mls qos cos override and the mls qos trust [cos | dscp] interface commands when  
pass-through mode is enabled, pass-through mode is disabled.  
If you enter the mls qos trust cos pass-through dscp interface configuration command when the mls  
qos cos override and the mls qos trust [cos | dscp] interface commands are already configured,  
pass-through mode is disabled.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Configuring a QoS Policy  
Configuring a QoS policy typically requires classifying traffic into classes, configuring policies applied  
to those traffic classes, and attaching policies to interfaces.  
For background information, see the “Classification” section on page 23-4 and the “Policing and  
Marking” section on page 23-6.  
This section contains this configuration information:  
•
•
•
Classifying Traffic by Using ACLs, page 23-23  
Classifying Traffic by Using Class Maps, page 23-27  
Classifying, Policing, and Marking Traffic by Using Policy Maps, page 23-28  
Classifying Traffic by Using ACLs  
You can classify IP traffic by using IP standard or IP extended ACLs; you can classify Layer 2 traffic  
by using Layer 2 MAC ACLs.  
Beginning in privileged EXEC mode, follow these steps to create an IP standard ACL for IP traffic:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
access-list access-list-number {permit |  
remark} {source source-wildcard | host  
source | any}  
Create an IP standard ACL, repeating the command as many times as  
necessary.  
For access-list-number, enter the ACL number. The range is 1 to 99 and  
1300 to 1999.  
Enter permit to specify whether to permit access if conditions are  
matched.  
Enter remark to specify an ACL entry comment up to 100 characters.  
Note  
Deny statements are not supported for QoS ACLs. See the  
“Classification Based on QoS ACLs” section on page 23-5 for  
more details.  
The source is the source address of the network or host from which the  
packet is being sent, specified in one of three ways:  
•
•
The 32-bit quantity in dotted decimal format.  
The keyword any as an abbreviation for source and  
source-wildcard of 0.0.0.0 255.255.255.255. You do not need to  
enter a source wildcard.  
•
The keyword host as an abbreviation for source and  
source-wildcard of source 0.0.0.0.  
(Optional) The source-wildcard variable applies wildcard bits to the  
source (see first bullet item).  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show access-lists  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
For more information about creating IP standard ACLs, see the “Guidelines for Applying ACLs to  
Physical Interfaces” section on page 22-5.  
To delete an ACL, use the no access-list access-list-number global configuration command.  
This example shows how to allow access for only those hosts on the two specified networks. The  
wildcard bits apply to the host portions of the network addresses. Any host with a source address that  
does not match the ACL statements is rejected.  
Switch(config)# access-list 1 permit 192.5.255.0 0.0.0.255  
Switch(config)# access-list 1 permit 36.0.0.0 0.0.0.255  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Beginning in privileged EXEC mode, follow these steps to create an IP extended ACL for IP traffic:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
access-list access-list-number  
{permit | remark} protocol  
Create an IP extended ACL, repeating the command as many times as  
necessary.  
{source source-wildcard | host source |  
any} [operator port] {destination  
destination-wildcard | host destination |  
any} [operator port] [dscp dscp-value]  
[time-range time-range-name]  
For access-list-number, enter the ACL number. The range is 100 to 199  
and 2000 to 2699.  
Enter permit to permit access if conditions are matched.  
Enter remark to specify an ACL entry comment up to 100 characters.  
Note  
Deny statements are not supported for QoS ACLs. See the  
“Classification Based on QoS ACLs” section on page 23-5 for  
more details.  
For protocol, enter the name or number of an IP protocol. Use the  
question mark (?) to see a list of available protocol keywords.  
For source, enter the network or host from which the packet is being  
sent. For source-wildcard, enter the wildcard bits by placing ones in the  
bit positions that you want to ignore. You specify the source and  
source-wilcard by using dotted decimal notation, by using the any  
keyword as an abbreviation for source 0.0.0.0 source-wildcard  
255.255.255.255, or by using the host keyword for source 0.0.0.0.  
For destination, enter the network or host to which the packet is being  
sent. You have the same options for specifying the destination and  
destination-wildcard as those described for source and  
source-wildcard.  
Define a destination or source port.  
•
•
The operator can be only eq (equal).  
If operator is after source source-wildcard, conditions match when  
the source port matches the defined port.  
•
•
If operator is after destination destination-wildcard, conditions  
match when the destination port matches the defined port.  
The port is a decimal number or name of a TCP or UDP port. The  
number can be from 0 to 65535.  
•
•
Use TCP port names only for TCP traffic.  
Use UDP port names only for UDP traffic.  
Enter dscp to match packets with any of the 13 supported DSCP values  
(0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48, and 56) or use the question  
mark (?) to see a list of available values.  
The time-range keyword is optional. For information about this  
keyword, see the “Applying Time Ranges to ACLs” section on  
page 22-14.  
Step 3  
end  
Return to privileged EXEC mode.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Command  
Purpose  
Step 4  
show access-lists  
Verify your entries.  
Step 5  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
For more information about creating IP extended ACLs, see the “Guidelines for Applying ACLs to  
Physical Interfaces” section on page 22-5.  
To delete an ACL, use the no access-list access-list-number global configuration command.  
This example shows how to create an ACL that permits only TCP traffic from the destination IP address  
128.88.1.2 with TCP port number 25:  
Switch(config)# access-list 102 permit tcp 0.0.0.0 255.255.255.255 128.88.1.2 0.0.0.0 eq  
25  
Beginning in privileged EXEC mode, follow these steps to create a Layer 2 MAC ACL for Layer 2  
traffic:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
mac access-list extended name  
Create a Layer 2 MAC ACL by specifying the name of the list.  
After entering this command, the mode changes to extended MAC  
ACL configuration.  
Step 3  
permit {any | host source MAC address}  
{any | host destination MAC address} [aarp  
| amber | appletalk | dec-spanning |  
decnet-iv | diagnostic | dsm | etype-6000 |  
etype-8042 | lat | lavc-sca | mop-console |  
mop-dump | msdos | mumps | netbios |  
vines-echo |vines-ip | xns-idp]  
Enter permit to permit access if conditions are matched.  
Note  
Deny statements are not supported for QoS ACLs. See the  
“Classification Based on QoS ACLs” section on page 23-5  
for more details.  
For source MAC address, enter the MAC address of the host from  
which the packet is being sent. You specify this by using the any  
keyword to deny any source MAC address or by using the host  
keyword and the source in the hexadecimal format (H.H.H).  
For destination MAC address, enter the MAC address of the host to  
which the packet is being sent. You specify this by using the any  
keyword to deny any destination MAC address or by using the host  
keyword and the destination in the hexadecimal format (H.H.H).  
(Optional) You can also enter these options:  
aarp | amber | appletalk | dec-spanning | decnet-iv |  
diagnostic | dsm | etype-6000 | etype-8042 | lat | lavc-sca |  
mop-console | mop-dump | msdos | mumps | netbios |  
vines-echo |vines-ip | xns-idp (a non-IP protocol).  
Step 4  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show access-lists [number | name]  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
For more information about creating MAC extended ACLs, see the “Creating Named MAC Extended  
ACLs” section on page 22-17.  
To delete an ACL, use the no mac access-list extended name global configuration command.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
This example shows how to create a Layer 2 MAC ACL with a permit statement. The statement allows  
traffic from the host with MAC address 0001.0000.0001 to the host with MAC address 0002.0000.0001.  
Switch(config)# mac access-list extended maclist1  
Switch(config-ext-macl)# permit host 0001.0000.0001 host 0002.0000.0001  
Classifying Traffic by Using Class Maps  
You use the class-map global configuration command to isolate a specific traffic flow (or class) from  
all other traffic and to name it. The class map defines the criteria to use to match against a specific traffic  
flow to further classify it. Match statements can only include ACLs. The match criterion is defined with  
one match statement entered within the class-map configuration mode.  
Note  
You can also create class maps during policy map creation by using the class policy-map configuration  
command. For more information, see the “Classifying, Policing, and Marking Traffic by Using Policy  
Maps” section on page 23-28.  
Beginning in privileged EXEC mode, follow these steps to create a class map and to define the match  
criterion to classify traffic:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
access-list access-list-number permit  
{source source-wildcard | host source |  
any}  
Create an IP standard or extended ACL for IP traffic or a Layer 2 MAC  
ACL for non-IP traffic, repeating the command as many times as  
necessary.  
or  
For more information, see the “Guidelines for Applying ACLs to  
Physical Interfaces” section on page 22-5 and the “Classifying Traffic  
by Using ACLs” section on page 23-23.  
access-list access-list-number  
{permit | remark} protocol  
{source source-wildcard | host source |  
any} [operator port] {destination  
destination-wildcard | host destination |  
any} [operator port] [dscp dscp-value]  
[time-range time-range-name]  
For more information on the mac access-list extended name  
command, see the “Creating Named MAC Extended ACLs” section on  
page 22-17.  
Note  
Deny statements are not supported for QoS ACLs. See the  
“Classification Based on QoS ACLs” section on page 23-5 for  
more details.  
or  
mac access-list extended name  
permit {any | host source MAC address}  
{any | host destination MAC address}  
[aarp | amber | dec-spanning | decnet-iv |  
diagnostic | dsm | etype-6000 | etype-8042  
| lat | lavc-sca | mop-console | mop-dump  
| msdos | mumps | netbios | vines-echo  
|vines-ip | xns-idp]  
Step 3  
class-map class-map-name  
Create a class map, and enter class-map configuration mode.  
By default, no class maps are defined.  
For class-map-name, specify the name of the class map.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Command  
Purpose  
Step 4  
match {access-group acl-index |  
access-group name acl-name | ip dscp  
dscp-list}  
Define the match criterion to classify traffic.  
By default, no match criterion is supported.  
Only one match criterion per class map is supported, and only one ACL  
per class map is supported.  
For access-group acl-index or access-group name acl-name, specify  
the number or name of the ACL created in Step 3.  
For ip dscp dscp-list, enter a list of up to eight IP DSCP values for each  
match statement to match against incoming packets. Separate each  
value with a space. The supported DSCP values are 0, 8, 10, 16, 18, 24,  
26, 32, 34, 40, 46, 48, and 56.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show class-map [class-map-name]  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To delete an existing class map, use the no class-map class-map-name global configuration command.  
To remove a match criterion, use the no match {access-group acl-index | name acl-name | ip dscp}  
class-map configuration command.  
This example shows how to configure the class map called class1. The class1 has one match criterion,  
which is an ACL called 103.  
Switch(config)# access-list 103 permit any any tcp eq 80  
Switch(config)# class-map class1  
Switch(config-cmap)# match access-group 103  
Switch(config-cmap)# end  
Switch#  
Classifying, Policing, and Marking Traffic by Using Policy Maps  
A policy map specifies which traffic class to act on. Actions can include setting a specific DSCP value  
in the traffic class and specifying the traffic bandwidth limitations for each matched traffic class  
(policer) and the action to take when the traffic is out of profile (marking or dropping).  
A policy map also has these characteristics:  
•
•
A policy map can contain multiple class statements, each with different match criteria and policers.  
A separate policy-map class can exist for each type of traffic received through an interface.  
You can attach only one policy map per interface in the input direction.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Beginning in privileged EXEC mode, follow these steps to create a policy map:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
access-list access-list-number permit  
{source source-wildcard | host source |  
any}  
Create an IP standard or extended ACL for IP traffic or a Layer 2 MAC  
ACL for non-IP traffic, repeating the command as many times as  
necessary.  
or  
For more information, see the “Classifying Traffic by Using ACLs”  
section on page 23-23.  
access-list access-list-number  
{permit | remark} protocol  
Note  
Deny statements are not supported for QoS ACLs. See the  
“Classification Based on QoS ACLs” section on page 23-5 for  
more details.  
{source source-wildcard | host source |  
any} [operator port] {destination  
destination-wildcard | host destination |  
any} [operator port] [dscp dscp-value]  
[time-range time-range-name]  
For more information on the mac access-list extended name  
command, see the “Creating Named MAC Extended ACLs” section on  
page 22-17.  
or  
mac access-list extended name  
permit {any | host source MAC address}  
{any | host destination MAC address}  
[aarp | amber | appletalk |dec-spanning |  
decnet-iv | diagnostic | dsm | etype-6000 |  
etype-8042 | lat | lavc-sca | mop-console |  
mop-dump | msdos | mumps | netbios |  
vines-echo |vines-ip | xns-idp]  
Step 3  
Step 4  
policy-map policy-map-name  
Create a policy map by entering the policy map name, and enter  
policy-map configuration mode.  
By default, no policy maps are defined.  
The default behavior of a policy map is to set the DSCP to 0 if the  
packet is an IP packet and to set the CoS to 0 if the packet is tagged. No  
policing is performed.  
class class-map-name [access-group name Define a traffic classification, and enter policy-map class configuration  
acl-index-or-name]  
mode.  
By default, no policy map class maps are defined.  
If a traffic class has already been defined by using the class-map global  
configuration command, specify its name for class-map-name in this  
command.  
For access-group name acl-index-or-name, specify the number or name  
of the ACL created in Step 2.  
Note  
In a policy map, the class named class-default is not supported.  
The switch does not filter traffic based on the policy map  
defined by the class class-default policy-map configuration  
command.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Command  
Purpose  
Step 5  
set {ip dscp new-dscp}  
Classify IP traffic by setting a new value in the packet.  
For ip dscp new-dscp, enter a new DSCP value to be assigned to the  
classified traffic. The supported DSCP values are 0, 8, 10, 16, 18, 24,  
26, 32, 34, 40, 46, 48, and 56.  
Step 6  
police rate-bps burst-byte [exceed-action Define a policer for the classified traffic.  
{drop | dscp dscp-value}]  
You can configure up to 60 policers on ingress Gigabit-capable  
Ethernet ports.  
For rate-bps, specify average traffic rate in bits per second (bps). The  
range is 8 Mbps to 1000 Mbps for the Gigabit-capable Ethernet ports.  
For burst-byte, specify the normal burst size in bytes. The values  
supported on the Gigabit-capable Ethernet ports are 4096, 8192, 16348,  
32768, 65536, 131072, 262144, and 524288.  
(Optional) Specify the action to take when the rates are exceeded. Use  
the exceed-action drop keywords to drop the packet. Use the  
exceed-action dscp dscp-value keywords to mark down the DSCP  
value and send the packet.  
Step 7  
Step 8  
Step 9  
exit  
Return to policy-map configuration mode.  
Return to global configuration mode.  
exit  
interface interface-id  
Specify the interface to attach to the policy map, and enter interface  
configuration mode.  
Valid interfaces include physical interfaces.  
Step 10  
service-policy input policy-map-name  
Apply specified policy map to the input of a particular interface.  
Only one policy map per interface per direction is supported.  
Return to privileged EXEC mode.  
Step 11  
Step 12  
end  
show policy-map [policy-map-name class Verify your entries.  
class-name]  
Step 13  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To delete an existing policy map, use the no policy-map policy-map-name global configuration  
command. To delete an existing class map, use the no class class-map-name policy-map configuration  
command. To remove an assigned DSCP value, use the no set ip dscp new-dscp policy-map  
configuration command. To remove an existing policer, use the no police rate-bps burst-byte  
[exceed-action {drop | dscp dscp-value}] policy-map configuration command. To remove the policy  
map and interface association, use the no service-policy input policy-map-name interface configuration  
command.  
For details about configuring policy maps and security ACLs on the same interface, see Table 23-5 on  
page 23-17.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
This example shows how to create a policy map and attach it to an ingress interface. In the configuration,  
the IP standard ACL permits traffic from network 10.1.0.0. For traffic matching this classification, the  
DSCP value in the incoming packet is trusted. If the matched traffic exceeds an average traffic rate  
of 5000000 bps and a normal burst size of 8192 bytes, its DSCP is marked down to a value of 10 and sent.  
Switch(config)# access-list 1 permit 10.1.0.0 0.0.255.255  
Switch(config)# class-map ipclass1  
Switch(config-cmap)# match access-group 1  
Switch(config-cmap)# exit  
Switch(config)# policy-map flow1t  
Switch(config-pmap)# class ipclass1  
Switch(config-pmap-c)# police 5000000 8192 exceed-action dscp 10  
Switch(config-pmap-c)# exit  
Switch(config-pmap)# exit  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# switchport mode access  
Switch(config-if)# service-policy input flow1t  
This example shows how to create a Layer 2 MAC ACL with two permit statements and attach it to an  
ingress interface. The first permit statement allows traffic from the host with MAC  
address 0001.0000.0001 destined for the host with MAC address 0002.0000.0001.  
Switch(config)# mac access-list extended maclist1  
Switch(config-ext-mac)# permit host 0001.0000.0001 host 0002.0000.0001  
Switch(config-ext-mac)# exit  
Switch(config)# mac access-list extended maclist2  
Switch(config-ext-mac)# permit host 0001.0000.0003 host 0002.0000.0003  
Switch(config-ext-mac)# exit  
Switch(config)# class-map macclass1  
Switch(config-cmap)# match access-group name maclist1  
Switch(config-cmap)# exit  
Switch(config)# policy-map macpolicy1  
Switch(config-pmap)# class macclass1  
Switch(config-pmap-c)# set ip dscp 56  
Switch(config-pmap-c)# exit  
Switch(config-pmap)# class macclass2 maclist2  
Switch(config-pmap-c)# set ip dscp 48  
Switch(config-pmap-c)# exit  
Switch(config-pmap)# exit  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# switchport mode trunk  
Switch(config-if)# mls qos trust cos  
Switch(config-if)# service-policy input macpolicy1  
Configuring CoS Maps  
This section describes how to configure the CoS maps:  
•
•
Configuring the CoS-to-DSCP Map, page 23-32  
Configuring the DSCP-to-CoS Map, page 23-33  
All the maps are globally defined.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Configuring the CoS-to-DSCP Map  
You use the CoS-to-DSCP map to map CoS values in incoming packets to a DSCP value that QoS uses  
internally to represent the priority of the traffic.  
Table 23-7 shows the default CoS-to-DSCP map.  
Table 23-7  
Default CoS-to-DSCP Map  
CoS Value  
DSCP Value  
0
1
2
3
4
5
6
7
0
8
16  
24  
32  
40  
48  
56  
If these values are not appropriate for your network, you need to modify them.  
Beginning in privileged EXEC mode, follow these steps to modify the CoS-to-DSCP map:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Modify the CoS-to-DSCP map.  
mls qos map cos-dscp dscp1...dscp8  
For dscp1...dscp8, enter 8 DSCP values that correspond to CoS values 0  
to 7. Separate each DSCP value with a space.  
The supported DSCP values are 0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48,  
and 56.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show mls qos maps cos-dscp  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return to the default map, use the no mls qos map cos-dscp global configuration command.  
This example shows how to modify and display the CoS-to-DSCP map:  
Switch# configure terminal  
Switch(config)# mls qos map cos-dscp 8 8 8 8 24 32 56 56  
Switch(config)# end  
Switch# show mls qos maps cos-dscp  
Cos-dscp map:  
cos: 0 1 2 3 4 5 6 7  
--------------------------------  
dscp: 8 8 8 8 24 32 56 56  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Configuring the DSCP-to-CoS Map  
You use the DSCP-to-CoS map to map DSCP values in incoming packets to a CoS value, which is used  
to select one of the four egress queues.  
The switch supports these DSCP values: 0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48, and 56.  
Table 23-8 shows the default DSCP-to-CoS map.  
Table 23-8  
Default DSCP-to-CoS Map  
DSCP Values  
0
CoS Value  
0
1
2
3
4
5
6
7
8, 10  
16, 18  
24, 26  
32, 34  
40, 46  
48  
56  
If these values are not appropriate for your network, you need to modify them.  
Beginning in privileged EXEC mode, follow these steps to modify the DSCP-to-CoS map:  
Command  
configure terminal  
mls qos map dscp-cos dscp-list to cos Modify the DSCP-to-CoS map.  
For dscp-list, enter up to 13 DSCP values separated by spaces. Then enter  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
the to keyword.  
For cos, enter the CoS value to which the DSCP values correspond.  
The supported DSCP values are 0, 8, 10, 16, 18, 24, 26, 32, 34, 40, 46, 48,  
and 56. The CoS range is 0 to 7.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show mls qos maps dscp-cos  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return to the default map, use the no mls qos map dscp-cos global configuration command.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
This example shows how the DSCP values 26 and 48 are mapped to CoS value 7. For the remaining  
DSCP values, the DSCP-to-CoS mapping is the default.  
Switch(config)# mls qos map dscp-cos 26 48 to 7  
Switch(config)# exit  
Switch# show mls qos maps dscp-cos  
Dscp-cos map:  
dscp: 0 8 10 16 18 24 26 32 34 40 46 48 56  
-----------------------------------------------  
cos: 0 1 1 2 2 3 7 4 4 5 5 7 7  
Configuring the Egress Queues  
This section describes how to configure the egress queues:  
•
•
•
Configuring CoS Priority Queues, page 23-34  
Configuring WRR Priority, page 23-35  
Enabling the Expedite Queue and Configuring WRR Priority, page 23-35  
For more information about the egress queues, see the “Egress CoS Queues” section on page 23-8.  
Configuring CoS Priority Queues  
Beginning in privileged EXEC mode, follow these steps to configure the CoS priority queues:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
wrr-queue cos-map qid cos1...cosn  
Specify the queue ID of the CoS priority queue. (Ranges are 1 to 4 where  
1 is the lowest CoS priority queue.)  
Specify the CoS values that are mapped to the queue id.  
Default values are as follows:  
CoS Value  
0, 1  
CoS Priority Queues  
1
2
3
4
2, 3  
4, 5  
6, 7  
Step 3  
Step 4  
end  
Return to privileged EXEC mode.  
show wrr-queue cos-map  
Display the mapping of the CoS priority queues.  
To disable the new CoS settings and return to default settings, use the no wrr-queue cos-map global  
configuration command.  
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Chapter 23 Configuring QoS  
Configuring Standard QoS  
Configuring WRR Priority  
Beginning in privileged EXEC mode, follow these steps to configure the WRR priority:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
Assign WRR weights to the four CoS queues.  
These are the ranges for the WRR values:  
wrr-queue bandwidth  
weight1...weight4  
•
•
For weight1, weight2, and weight3, the range is 1 to 255.  
For weight4, the range is 0 to 255. When weight4 is set to 0, queue  
4 is configured as the expedite queue.  
Note  
Step 3  
Step 4  
end  
Return to privileged EXEC mode.  
show wrr-queue bandwidth  
Display the WRR bandwidth allocation for the CoS priority queues.  
To disable the WRR scheduling and enable the strict priority scheduling, use the no wrr-queue  
bandwidth global configuration command.  
To enable one of the queues as the expedite queue and to enable the WRR scheduling for the remaining  
queues, see the “Enabling the Expedite Queue and Configuring WRR Priority” section on page 23-35.  
Enabling the Expedite Queue and Configuring WRR Priority  
Beginning in privileged EXEC mode, follow these steps to enable the expedite queue (queue 4) and  
assign WRR priority to the remaining queues:  
Command  
configure terminal  
wrr-queue bandwidth weight1 weight2 Configure queue 4 as the expedite queue and assign WRR weights to the  
Purpose  
Step 1  
Step 2  
Enter global configuration mode.  
weight3 0  
remaining egress queues.  
The range of WRR weights for weight1, weight2, and weight3 is 1 to 255.  
Return to privileged EXEC mode.  
Step 3  
Step 4  
end  
show wrr-queue bandwidth  
Display the WRR bandwidth allocation for the CoS priority queues.  
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Chapter 23 Configuring QoS  
Displaying Standard QoS Information  
Displaying Standard QoS Information  
To display standard QoS information, use one or more of the privileged EXEC commands in Table 23-9:  
Table 23-9  
Commands for Displaying QoS Information  
Command  
Purpose  
show class-map [class-map-name]  
Display QoS class maps, which define the match criteria to  
classify traffic.  
show policy-map [policy-map-name [class class-name]] Display QoS policy maps, which define classification criteria for  
incoming traffic.  
show mls qos maps [cos-dscp | dscp-cos]  
Display QoS mapping information. Maps are used to generate an  
internal DSCP value, which represents the priority of the traffic.  
show mls qos interface [interface-id] [policers]  
Display QoS information at the interface level, including the  
configuration of the egress queues and the CoS-to-egress-queue  
map, which interfaces have configured policers, and ingress  
statistics.  
show mls masks [qos | security]  
Display details regarding the masks1 used for QoS and security  
ACLs.  
show wrr-queue cos-map  
show wrr-queue bandwidth  
Display the mapping of the CoS priority queues.  
Display the WRR bandwidth allocation for the CoS priority  
queues.  
1. Access control parameters are called masks in the switch CLI commands and output.  
Standard QoS Configuration Examples  
This section shows a QoS migration path to help you quickly implement QoS features based on your  
existing network and planned changes to your network, as shown in Figure 23-5. It contains this  
information:  
•
•
QoS Configuration for the Existing Wiring Closet, page 23-37  
QoS Configuration for the Intelligent Wiring Closet, page 23-38  
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Chapter 23 Configuring QoS  
Standard QoS Configuration Examples  
Figure 23-5  
QoS Configuration Example Network  
Cisco router  
To Internet  
Gigabit Ethernet 0/5  
Catalyst 3550-12G switch  
Gigabit Ethernet 0/2  
Gigabit Ethernet 0/1  
Existing wiring closet  
Catalyst 2900 and 3500 XL  
switches  
Trunk  
link  
Trunk  
link  
BladeCenter  
End  
stations  
QoS Configuration for the Existing Wiring Closet  
Figure 23-5 shows an existing wiring closet with Catalyst 2900 XL and 3500 XL switches, for example.  
These switches are running Cisco IOS Release 12.0(5)XP or later, which supports the QoS-based  
IEEE 802.1p CoS values. QoS classifies frames by assigning priority-indexed CoS values to them and  
gives preference to higher-priority traffic.  
Recall that on the Catalyst 2900 and 3500 XL switches, you can classify untagged (native) Ethernet  
frames at the ingress ports by setting a default CoS priority (switchport priority default  
default-priority-id interface configuration command) for each port. For IEEE 802.1Q frames with tag  
information, the priority value from the header frame is used. On the Catalyst 3524-PWR XL and 3548  
XL switches, you can override this priority with the default value by using the switchport priority  
default override interface configuration command. For Catalyst 2950 and Catalyst 2900 XL switches  
and other 3500 XL models that do not have the override feature, the Catalyst 3550-12T switch at the  
distribution layer can override the IEEE 802.1p CoS value by using the mls qos cos override interface  
configuration command.  
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Chapter 23 Configuring QoS  
Standard QoS Configuration Examples  
For the Catalyst 2900 and 3500 XL switches, CoS configures each transmit port (the egress port) with a  
normal-priority transmit queue and a high-priority transmit queue, depending on the frame tag or the port  
information. Frames in the normal-priority queue are forwarded only after frames in the high-priority  
queue are forwarded. Frames that have IEEE 802.1p CoS values of 0 to 3 are placed in the  
normal-priority transmit queue while frames with CoS values of 4 to 7 are placed in the expedite  
(high-priority) queue.  
QoS Configuration for the Intelligent Wiring Closet  
Figure 23-5 shows an intelligent wiring closet with Catalyst 2950 switches, for example. One of the  
switches is connected to a video server, which has an IP address of 172.20.10.16.  
The object of this example is to prioritize the video traffic over all other traffic. To do so, a DSCP of 46  
is assigned to the video traffic. This traffic is stored in queue 4, which is serviced more frequently than  
the other queues.  
Beginning in privileged EXEC mode, follow these steps to configure the switch to prioritize video  
packets over all other traffic:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
access-list 1 permit 172.20.10.16  
Define an IP standard ACL, and permit traffic from the video  
server at 172.20.10.16.  
Step 3  
Step 4  
class-map videoclass  
match access-group 1  
Create a class map called videoclass, and enter class-map  
configuration mode.  
Define the match criterion by matching the traffic specified by  
ACL 1.  
Step 5  
Step 6  
exit  
Return to global configuration mode.  
policy-map videopolicy  
Create a policy map called videopolicy, and enter policy-map  
configuration mode.  
Step 7  
Step 8  
Step 9  
class videoclass  
Specify the class on which to act, and enter policy-map class  
configuration mode.  
set ip dscp 46  
For traffic matching ACL 1, set the DSCP of incoming packets to  
46.  
police 5000000 8192 exceed-action drop  
Define a policer for the classified video traffic to drop traffic that  
exceeds 5-Mbps average traffic rate with an 8192-byte burst size.  
Step 10  
Step 11  
Step 12  
exit  
Return to policy-map configuration mode.  
Return to global configuration mode.  
exit  
interface interface-id  
Specify the switch ingress interface that is connected to the video  
server, and enter interface configuration mode.  
Step 13  
Step 14  
Step 15  
Step 16  
service-policy input videopolicy  
exit  
Apply the policy to the ingress interface.  
Return to global configuration mode.  
Assign a higher WRR weight to queue 4.  
wrr-queue bandwidth 1 2 3 4  
wrr-queue cos-map 4 6 7  
Configure the CoS-to-egress-queue map so that CoS values 6  
and 7 select queue 4.  
Step 17  
end  
Return to privileged EXEC mode.  
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Chapter 23 Configuring QoS  
Standard QoS Configuration Examples  
Command  
Purpose  
Step 18  
Step 19  
show class-map videoclass  
Verify your entries.  
show policy-map videopolicy  
show mls qos maps [cos-dscp | dscp-cos]  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Standard QoS Configuration Examples  
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C H A P T E R  
24  
Configuring EtherChannels and Layer 2 Trunk  
Failover  
This chapter describes how to configure EtherChannel on the switch Layer 2 interfaces and Layer 2 trunk  
failover on Cisco Systems Intelligent Gigabit Ethernet Switch Modules.  
This chapter consists of these sections:  
•
•
•
•
•
•
•
Understanding EtherChannels, page 24-1  
EtherChannel On Mode, page 24-6  
Configuring EtherChannels, page 24-8  
Displaying EtherChannel, PAgP, and LACP Status, page 24-15  
Understanding Layer 2 Trunk Failover, page 24-15  
Configuring Layer 2 Trunk Failover, page 24-16  
Displaying Layer 2 Trunk Failover Status, page 24-18  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release.  
Understanding EtherChannels  
EtherChannel provides fault-tolerant high-speed links between switches, routers, and servers. You can  
use it to increase the bandwidth among the wiring closets and the data center, and you can deploy it  
anywhere in the network where bottlenecks are likely to occur. EtherChannel provides automatic  
recovery for the loss of a link by redistributing the load across the remaining links. If a link fails,  
EtherChannel redirects traffic from the failed link to the remaining links in the channel without  
intervention.  
An EtherChannel consists of individual Gigabit Ethernet links bundled into a single logical link as  
shown in Figure 24-1. The EtherChannel provides up to 4 Gbps (Gigabit EtherChannel) full-duplex  
bandwidth between your switch and another switch or host.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Understanding EtherChannels  
Figure 24-1  
Typical EtherChannel Configuration  
Catalyst 8500, 6000,  
5500, or 4000  
series switch  
Gigabit EtherChannel  
1000BASE-X  
BladeCenter  
Note  
The network device to which your switch is connected can impose its own limits on the number of  
interfaces in the EtherChannel. The number of EtherChannels is limited to six with eight ports per  
EtherChannel.  
You can configure an EtherChannel in one of these modes: Port Aggregation Protocol (PAgP), Link  
Aggregation Control Protocol (LACP), or On mode. Configure both ends of the EtherChannel in the  
same mode:  
•
When you configure one end of an EtherChannel in either PAgP or LACP mode, the system  
negotiates with the other end of the channel to determine which ports should become active.  
Incompatible ports are suspended.  
•
When you configure an EtherChannel in the on mode, no negotiations take place. The switch forces  
all compatible ports to become active in the EtherChannel. The other end of the channel (on the other  
switch) must also be configured in the on mode; otherwise, packet loss can occur.  
If a link within an EtherChannel fails, traffic previously carried over that failed link moves to the  
remaining links within the EtherChannel. If traps are enabled on the switch, a trap is sent for a failure  
that identifies the switch, the EtherChannel, and the failed link. Inbound broadcast and multicast packets  
on one link in an EtherChannel are blocked from returning on any other link of the EtherChannel.  
Understanding Port-Channel Interfaces  
When you create an EtherChannel for Layer 2 interfaces, a logical interface is dynamically created, as  
shown in Figure 24-2. You then manually assign an interface to the EtherChannel by using the  
channel-group interface configuration command.  
Each EtherChannel has a logical port-channel interface numbered from 1 to 6.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Understanding EtherChannels  
Figure 24-2  
Relationship of Physical Ports, Logical Port Channels, and Channel Groups  
Logical  
port-channel  
Channel-group  
binding  
Physical ports  
When a port joins an EtherChannel, the physical interface for that port is shut down. When the port  
leaves the port-channel, its physical interface is brought up, and it has the same configuration as it had  
before joining the EtherChannel.  
Note  
Configuration changes made to the logical interface of an EtherChannel might not propagate to all the  
member ports of the channel.  
Understanding the Port Aggregation Protocol and Link Aggregation Protocol  
The Port Aggregation Protocol (PAgP) and Link Aggregation Control Protocol (LACP) facilitate the  
automatic creation of EtherChannels by exchanging packets between Ethernet interfaces. PAgP is a  
Cisco-proprietary protocol that can be run only on Cisco switches and on those switches licensed by  
licensed vendors to support PAgP. LACP is defined in IEEE 802.3ad and allows Cisco switches to  
manage Ethernet channels between switches that conform to the IEEE 802.3ad protocol.  
By using one of these protocols, a switch learns the identity of partners capable of supporting either  
PAgP or LACP and learns the capabilities of each interface. It then dynamically groups similarly  
configured interfaces into a single logical link (channel or aggregate port). These interfaces are grouped  
based on hardware, administrative, and port parameter constraints. For example, PAgP groups the  
interfaces with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type.  
After grouping the links into an EtherChannel, PAgP adds the group to the spanning tree as a single  
switch port.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Understanding EtherChannels  
PAgP and LACP Modes  
Table 24-1 shows the user-configurable EtherChannel modes for the channel-group interface  
configuration command. Switch interfaces exchange PAgP packets only with partner interfaces  
configured in the auto or desirable modes. Switch interfaces exchange LACP packets only with partner  
interfaces configured in the active or passive modes. Interfaces configured in the on mode do not  
exchange PAgP or LACP packets.  
Table 24-1  
EtherChannel Modes  
Mode  
Description  
active  
Places an interface into an active negotiating state, in which the interface starts  
negotiations with other interfaces by sending LACP packets.  
auto  
Places an interface into a passive negotiating state, in which the interface responds to PAgP  
packets it receives but does not start PAgP packet negotiation. This setting minimizes the  
transmission of PAgP packets.  
desirable Places an interface into an active negotiating state, in which the interface starts  
negotiations with other interfaces by sending PAgP packets.  
passive  
Places an interface into a passive negotiating state, in which the interface responds to  
LACP packets that it receives, but does not start LACP packet negotiation. This setting  
minimizes the transmission of LACP packets.  
Exchanging PAgP Packets  
Both the auto and desirable PAgP modes allow interfaces to negotiate with partner interfaces to  
determine if they can form an EtherChannel based on criteria such as interface speed and, for Layer 2  
EtherChannels, trunking state and VLAN numbers.  
Interfaces can form an EtherChannel when they are in different PAgP modes as long as the modes are  
compatible. For example:  
•
An interface in the desirable mode can form an EtherChannel with another interface that is in the  
desirable or auto mode.  
•
An interface in the auto mode can form an EtherChannel with another interface in the desirable  
mode.  
An interface in the auto mode cannot form an EtherChannel with another interface that is also in the  
auto mode because neither interface starts PAgP negotiation.  
If your switch is connected to a partner that is PAgP-capable, you can configure the switch interface for  
nonsilent operation by using the non-silent keyword. If you do not specify non-silent with the auto or  
desirable mode, silent mode is assumed.  
The silent mode is used when the switch is connected to a device that is not PAgP-capable and seldom,  
if ever, sends packets. An example of a silent partner is a file server or a packet analyzer that is not  
generating traffic. In this case, running PAgP on a physical port connected to a silent partner prevents  
that switch port from ever becoming operational; however, the silent setting allows PAgP to operate, to  
attach the interface to a channel group, and to use the interface for transmission.  
Note  
An EtherChannel cannot be configured in both the PAgP and LACP modes.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Understanding EtherChannels  
Exchanging LACP Packets  
Both the active and passive LACP modes allow interfaces to negotiate with partner interfaces to  
determine if they can form an EtherChannel based on criteria such as interface speed and, for Layer 2  
EtherChannels, trunking state, and VLAN numbers.  
Interfaces can form an EtherChannel when they are in different LACP modes as long as the modes are  
compatible. For example:  
•
An interface in the active mode can form an EtherChannel with another interface that is in the active  
mode.  
•
An interface in the active mode can form an EtherChannel with another interface in the passive  
mode.  
An interface in the passive mode cannot form an EtherChannel with another interface that is also in the  
passive mode because neither interface starts LACP negotiation.  
Note  
An EtherChannel cannot be configured in both the PAgP and LACP modes.  
Physical Learners and Aggregate-Port Learners  
Network devices are classified as PAgP physical learners or aggregate-port learners. A device is a  
physical learner if it learns addresses by physical ports and directs transmissions based on that  
knowledge. A device is an aggregate-port learner if it learns addresses by aggregate (logical) ports.  
When a device and its partner are both aggregate-port learners, they learn the address on the logical  
port-channel. The device sends packets to the source by using any of the interfaces in the EtherChannel.  
With aggregate-port learning, it is not important on which physical port the packet arrives.  
The switch uses source-MAC address distribution for a channel if it is connected to a physical learner  
even if you configure the switch for destination-MAC address distribution.  
These frame distribution mechanisms are possible for frame transmission:  
•
•
•
•
•
•
Load distribution based on the source-MAC address of the packet  
Load distribution based on the destination-MAC address of the packet  
Load distribution based on the XOR of the source-MAC address and destination-MAC address  
Load distribution based on the source-host IP address  
Load distribution based on the destination-host IP address  
Load distribution based on the XOR of the source-IP address and destination-IP address  
The switch supports up to eight ports in a PAgP group.  
PAgP and LACP Interaction with Other Features  
The Dynamic Trunking Protocol (DTP) and Cisco Discovery Protocol (CDP) send and receive packets  
over the physical interfaces in the EtherChannel. Trunk ports send and receive PAgP and LACP protocol  
data units (PDUs) on the lowest numbered VLAN.  
Spanning tree sends packets over a single physical interface in the EtherChannel, regarding the  
EtherChannel as one port.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Understanding EtherChannels  
PAgP sends and receives PAgP PDUs only from interfaces that have PAgP enabled for the auto or  
desirable mode. LACP sends and receives LACP PDUs only from interfaces that have LACP enabled  
for the active or passive mode.  
EtherChannel On Mode  
EtherChannel on mode can be used to manually configure an EtherChannel. The on mode forces a port  
to join an EtherChannel without negotiations. It can be useful if the remote device does not support  
PAgP or LACP. With the on mode, a usable EtherChannel exists only when both ends of the link are  
configured in the on mode.  
Ports that are configured with on mode in the same channel group must have compatible port  
characteristics, such as speed and duplex. Ports that are not compatible are suspended, even though they  
are configured with on mode.  
Caution  
You should exercise care when using the on mode. This is a manual configuration, and ports on both  
ends of the EtherChannel must have a similar configuration. If the group is misconfigured, packet loss  
or spanning-tree loops can occur.  
Understanding Load Balancing and Forwarding Methods  
EtherChannel balances the traffic load across the links in a channel by randomly associating a newly  
learned MAC address with one of the links in the channel.  
EtherChannel balances the traffic load across the links in a channel by reducing part of the binary pattern  
formed from the frame addresses to a numerical value that selects one of the links in the channel.  
EtherChannel load balancing can use MAC addresses or IP addresses, source or destination addresses,  
or both source and destination addresses. The selected mode applies to all EtherChannels configured on  
the switch. You configure the load balancing and forwarding method by using the port-channel  
load-balance global configuration command.  
With source-MAC address forwarding, packets forwarded to an EtherChannel are distributed across the  
ports in the channel based on the source-MAC address of the incoming packet. Therefore, to provide  
load balancing, packets from different hosts use different ports in the channel, but packets from the same  
host use the same port in the channel. The MAC address learned by the switch does not change.  
With destination-MAC address forwarding, packets forwarded to an EtherChannel are distributed across  
the ports in the channel based on the destination host MAC address of the incoming packet. Therefore,  
packets to the same destination are forwarded over the same port, and packets to a different destination  
might be sent on a different port in the channel. You configure the load balancing and forwarding method  
by using the port-channel load-balance global configuration command.  
Different load-balancing methods have different advantages. You should choose a particular  
load-balancing method based on the position of the switch in the network and the kind of traffic that  
needs to be load-distributed. In Figure 24-3, an EtherChannel of four workstations communicates with  
a router. Because the router is a single-MAC-address device, source-based forwarding on the switch  
EtherChannel ensures that the switch uses all available bandwidth to the router. The router is configured  
for destination-based forwarding because the large number of workstations ensures that the traffic is  
evenly distributed from the router EtherChannel.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Understanding EtherChannels  
Figure 24-3  
Load Distribution and Forwarding Methods  
BladeCenter  
EtherChannel  
Cisco router  
with destination-based  
forwarding enabled  
With source-and-destination MAC address forwarding, packets forwarded to an EtherChannel are  
distributed across the ports in the channel based on both the source and destination MAC addresses. This  
combination forwarding method can be used if it is not clear whether source-MAC or destination-MAC  
address forwarding is better suited on a particular switch.  
With source-IP address-based forwarding, packets forwarded to an EtherChannel are distributed across  
the ports in the EtherChannel based on the source-IP address of the incoming packet. Therefore, to  
provide load-balancing, packets from different IP addresses use different ports in the channel, but  
packets from the same IP address use the same port in the channel.  
With destination-IP address-based forwarding, packets forwarded to an EtherChannel are distributed  
across the ports in the EtherChannel based on the destination-IP address of the incoming packet.  
Therefore, to provide load-balancing, packets from the same IP source address sent to different IP  
destination addresses could be sent on different ports in the channel. But packets sent from different  
source-IP addresses to the same destination-IP address are always sent on the same port in the channel.  
With source-and-destination IP address-based forwarding, packets forwarded to an EtherChannel are  
distributed across the ports in the EtherChannel based on both the source and destination IP addresses  
of the incoming packet. This combination forwarding method can be used if it is not clear whether  
source-IP or destination-IP address-based forwarding is better suited on a particular switch.  
Use the option that provides the greatest variety in your configuration. For example, if the traffic on a  
channel is going only to a single MAC address, using the destination-MAC address always chooses the  
same link in the channel. Using source addresses or IP addresses might result in better load balancing.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Configuring EtherChannels  
Configuring EtherChannels  
These sections describe how to configure EtherChannel interfaces:  
•
•
•
•
•
Default EtherChannel Configuration, page 24-8  
EtherChannel Configuration Guidelines, page 24-8  
Configuring Layer 2 EtherChannels, page 24-9  
Configuring EtherChannel Load Balancing, page 24-11  
Configuring the PAgP Learn Method and Priority, page 24-12  
Note  
Note  
Make sure that the interfaces are correctly configured (see the “EtherChannel Configuration Guidelines”  
section on page 24-8).  
After you configure an EtherChannel, configuration changes applied to the port-channel interface apply  
to all the physical interfaces assigned to the port-channel interface, and configuration changes applied  
to the physical interface affect only the interface where you apply the configuration.  
Default EtherChannel Configuration  
Table 24-2 shows the default EtherChannel configuration.  
Table 24-2  
Default EtherChannel Configuration  
Feature  
Default Setting  
Channel groups  
PAgP mode  
None assigned.  
No default.  
PAgP learn method  
PAgP priority  
LACP learn method  
LACP priority  
Load balancing  
Aggregate-port learning on all interfaces.  
128 on all interfaces. (Changing this value has no effect.)  
Aggregate-port learning on all interfaces.  
32768 on all interfaces.  
Load distribution on the switch is based on the  
source-MAC address of the incoming packet.  
EtherChannel Configuration Guidelines  
If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops  
and other problems. Follow these guidelines to avoid configuration problems:  
•
•
•
Configure an EtherChannel with up to eight Ethernet ports of the same type.  
Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.  
Enable all interfaces in an EtherChannel. A port in an EtherChannel that is disabled by using the  
shutdown interface configuration command is treated as a link failure, and its traffic is transferred  
to one of the remaining interfaces in the EtherChannel.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Configuring EtherChannels  
•
When a group is first created, all ports follow the parameters set for the first port to be added to the  
group. If you change the configuration of one of these parameters, you must also make the changes  
to all ports in the group:  
–
–
–
–
Allowed-VLAN list  
Spanning-tree path cost for each VLAN  
Spanning-tree port priority for each VLAN  
Spanning-tree Port Fast setting  
•
•
Do not configure a secure port as part of an EtherChannel or the reverse.  
Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE  
802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears,  
and IEEE 802.1x is not enabled.  
•
•
If EtherChannels are configured on switch interfaces, remove the EtherChannel configuration from  
the interfaces before globally enabling IEEE 802.1x on a switch by using the dot1x  
system-auth-control global configuration command.  
An EtherChannel supports the same allowed range of VLANs on all the interfaces in a trunking  
Layer 2 EtherChannel. When configuring an interface for PAgP, if the allowed range of VLANs is  
not the same, the interfaces do not form an EtherChannel even when PAgP is set to the auto or  
desirable mode. When configuring an interface for LACP, if the allowed range of VLANs is not the  
same, the interfaces do not form an EtherChannel even when LACP is set to the active or passive  
mode.  
•
Interfaces with different spanning-tree path costs can form an EtherChannel if they are otherwise  
compatibly configured. Setting different spanning-tree path costs does not, by itself, make interfaces  
incompatible for the formation of an EtherChannel.  
Configuring Layer 2 EtherChannels  
You configure Layer 2 EtherChannels by configuring the Ethernet interfaces with the channel-group  
interface configuration command, which creates the port-channel logical interface. You cannot put a  
Layer 2 interface into a manually created port-channel interface.  
Note  
Layer 2 interfaces must be connected and functioning for the software to create port-channel interfaces.  
Beginning in privileged EXEC mode, follow these steps to assign a Layer 2 Ethernet interface to a  
Layer 2 EtherChannel:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify a physical interface to configure, and enter interface  
configuration mode.  
Valid interfaces include physical interfaces.  
Up to eight interfaces of the same type and speed can be  
configured for the same group.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Configuring EtherChannels  
Command  
Purpose  
Step 3  
Step 4  
switchport mode {access | trunk}  
Assign all interfaces as static-access ports in the same VLAN, or  
configure them as trunks.  
switchport access vlan vlan-id  
If you configure the interface as a static-access port, assign it to  
only one VLAN. The range is 1 to 4094.  
channel-group channel-group-number mode  
Assign the port to a channel group, and specify the PAgP or  
{{auto [non-silent] | desirable [non-silent] | on} | LACP mode.  
{active | passive}}  
For channel-group-number, the range is 1 to 6. Each  
EtherChannel can have up to eight compatibly configured  
Ethernet interfaces.  
For mode, select one of these keywords:  
•
•
•
•
auto—Enables PAgP only if a PAgP device is detected. It  
places an interface into a passive negotiating state, in which  
the interface responds to PAgP packets it receives but does  
not start PAgP packet negotiation.  
desirable—Unconditionally enables PAgP. It places an  
interface into an active negotiating state, in which the  
interface starts negotiations with other interfaces by sending  
PAgP packets.  
on—Forces the interface to channel without PAgP. With the  
on mode, a usable EtherChannel exists only when an  
interface group in the on mode is connected to another  
interface group in the on mode.  
non-silent—If your switch is connected to a partner that is  
PAgP-capable, you can configure the switch interface for  
nonsilent operation. You can configure an interface with the  
non-silent keyword for use with the auto or desirable mode.  
If you do not specify non-silent with the auto or desirable  
mode, silent is assumed. The silent setting is for connections  
to file servers or packet analyzers. This setting allows PAgP  
to operate, to attach the interface to a channel group, and to  
use the interface for transmission.  
•
•
active—Enables LACP only if an LACP device is detected.  
It places an interface into an active negotiating state, in  
which the interface starts negotiations with other interfaces  
by sending LACP packets.  
passive—Enables LACP on an interface and places it into a  
passive negotiating state, in which the interface responds to  
LACP packets that it receives, but does not start LACP  
packet negotiation.  
For information on compatible PAgP and LACP modes for the  
switch and its partner, see the “PAgP and LACP Modes” section  
on page 24-4.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Configuring EtherChannels  
To remove a port from the EtherChannel group, use the no channel-group interface configuration  
command. If you delete the EtherChannel by using the no interface port-channel global configuration  
command without removing the physical interfaces, the physical interfaces are shut down. If you do not  
want the member physical interfaces to shut down, remove the physical interfaces before deleting the  
EtherChannel.  
This example shows how to assign a range of interfaces as static-access ports in VLAN 10 to channel 5  
with the PAgP mode desirable:  
Switch# configure terminal  
Switch(config)# interface range gigabitethernet0/17 -18  
Switch(config-if-range)# switchport mode access  
Switch(config-if-range)# switchport access vlan 10  
Switch(config-if-range)# channel-group 5 mode desirable  
Switch(config-if-range)# end  
Configuring EtherChannel Load Balancing  
This section describes how to configure EtherChannel load balancing by using source-based or  
destination-based forwarding methods. For more information, see the “Understanding Load Balancing  
and Forwarding Methods” section on page 24-6.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Configuring EtherChannels  
Beginning in privileged EXEC mode, follow these steps to configure EtherChannel load balancing:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
port-channel load-balance method  
Configure an EtherChannel load-balancing method value:  
•
•
src-mac—Load distribution using the source-MAC address.  
dst-mac—Load distribution using the destination-MAC  
address.  
•
•
•
•
src-dst-mac—Load distribution is based on the XOR of the  
source-MAC address and destination MAC address.  
src-ip—Load distribution is based on the source-host IP  
address.  
dst-ip—Load distribution is based on the destination-host IP  
address.  
src-dst-ip—Load distribution is based on the XOR of the  
source-IP address and destination-IP address.  
The default is src-mac.  
If the link partner to the switch is a physical learner, use one of  
these load-distribution methods:  
•
If the channel-group interface configuration command is  
set to auto or desirable, the switch automatically uses the  
load distribution method based on the source-MAC address,  
regardless of the configured load-distribution method.  
•
If the channel-group interface configuration command is  
set to on, set the load-distribution method based on the  
source-MAC address by using the port-channel  
load-balance src-mac global configuration command.  
Step 3  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show etherchannel load-balance  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
To return EtherChannel load balancing to the default configuration, use the no port-channel  
load-balance global configuration command.  
Configuring the PAgP Learn Method and Priority  
Network devices are classified as PAgP physical learners or aggregate-port learners. A device is a  
physical learner if it learns addresses by physical ports and directs transmissions based on that  
knowledge. A device is an aggregate-port learner if it learns addresses by aggregate ports.  
For compatibility with Catalyst 1900 series switches, configure the switch for source-MAC load  
distribution.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Configuring EtherChannels  
The switch supports address learning only on aggregate ports even though the physical-port keyword  
is provided in the command-line interface (CLI). The pagp learn-method and the pagp port-priority  
interface configuration command have no effect on the switch hardware.  
Note  
You should not set the learn method to physical-port because the switch is an aggregate-learning  
device.  
If the link partner to the switch is a physical learner that has the channel-group interface configuration  
command set to auto or desirable, the switch automatically uses the load-distribution method based on  
the source-MAC address, regardless of the configured load distribution method.  
If the link partner to the switch is a physical learner that has the channel-group interface configuration  
command set to on, set the load-distribution method based on the source-MAC address by using the  
port-channel load-balance src-mac global configuration command.  
Configuring the LACP Port Priority  
You can set the priority for each port in an EtherChannel that is configured for LACP by using the  
lacp port-priority privileged EXEC command. The range is from 1 to 65535. Beginning in privileged  
EXEC mode, follow these steps to configure the LACP port priority:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
interface interface-id  
Specify the interface for transmission, and enter interface configuration  
mode.  
Step 3  
lacp port-priority priority-value  
Select the LACP port priority value.  
For priority-value, the range is 1 to 65535. By default, the priority value is  
32768. The lower the range, the more likely that the interface will be used  
for LACP transmission.  
Step 4  
Step 5  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
or  
show lacp channel-group-number  
internal  
Step 6  
copy running-config startup-config (Optional) Save your entries in the configuration file.  
Configuring Hot Standby Ports  
When enabled, LACP tries to configure the maximum number of LACP-compatible ports in a channel,  
up to a maximum of 16 ports. Only eight LACP links can be active at one time. Any additional links are  
put in a hot standby state. If one of the active links becomes inactive, a link that is in hot standby mode  
becomes active in its place.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Configuring EtherChannels  
If more than eight links are configured for an EtherChannel group, the software determines which of the  
hot standby ports to make active based on LACP port-priority and Port ID.  
All ports default to the same port priority. You can change the port priority of LACP EtherChannel ports  
to specify which hot standby links become active first by using the lacp port-priority interface  
configuration command to set the port priority to a value lower than the default of 32768.  
The hot standby ports that have lower port ID numbers become active in the channel first unless the port  
priority is configured to be a lower number than the default value of 32768.  
Note  
If LACP cannot aggregate all the ports that are compatible (for example, the remote system might have  
more restrictive hardware limitations), all the ports that cannot be actively included in the EtherChannel  
are put in a hot standby state. They are used only if one of the channeled ports fails.  
Configuring the LACP System Priority  
You can set the system priority for all of the EtherChannels that are configured for LACP by using the  
lacp system-priority privileged EXEC command. The range is from 1 to 65535.  
Note  
The lacp system-priority command is global. You cannot set a system priority for each  
LACP-configured channel separately.  
We recommend using this command only when there are a combination of LACP-configured  
EtherChannels that are in both active and standby modes.  
Beginning in privileged EXEC mode, follow these steps to configure the LACP system priority:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
lacp system-priority priority-value  
Select the LACP system priority value.  
For priority-value, the range is 1 to 65535. By default, the priority  
value is 32768. The lower the range, the higher the system priority.  
The switch with the lower system priority value determines which  
links between LACP partner switches are active and which are in  
standby for each LACP EtherChannel.  
Step 3  
Step 4  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
or  
show lacp channel-group-number internal  
copy running-config startup-config  
Step 5  
(Optional) Save your entries in the configuration file.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Displaying EtherChannel, PAgP, and LACP Status  
Displaying EtherChannel, PAgP, and LACP Status  
You can use the privileged EXEC commands described in Table 24-3 to display EtherChannel, PAgP,  
and LACP status information:  
Table 24-3  
Commands for Displaying EtherChannel, PAgP, and LACP Status  
Command  
Description  
show etherchannel [channel-group-number] {detail |  
load-balance | port | port-channel | summary}  
Displays EtherChannel information in a detailed and one-line  
summary form. Also displays the load-balance or  
frame-distribution scheme, port, and port-channel information.  
show pagp [channel-group-number] {counters |  
internal | neighbor}1  
Displays PAgP information such as traffic information, the  
internal PAgP configuration, and neighbor information.  
show lacp [channel-group-number] {counters |  
internal | neighbor}2  
Displays LACP information such as traffic information, the  
internal PAgP configuration, and neighbor information.  
1. You can clear PAgP channel-group information and traffic filters by using the clear pagp {channel-group-number [counters] | counters} privileged  
EXEC command.  
2. You can clear LACP channel-group information and traffic filters by using the clear lacp {channel-group-number [counters] | counters} privileged  
EXEC command.  
For detailed information about the fields in the command outputs, see the command reference for this  
release.  
Understanding Layer 2 Trunk Failover  
Layer 2 trunk failover, also known as link-state tracking, is a feature that provides Layer 2 redundancy  
in the network when used in conjunction with server NIC adapter teaming. When the server network  
adapters are configured in a primary or secondary relationship known as teaming, and if the link is lost  
on the primary interface, connectivity transparently changes to the secondary interface.  
When you enable Layer 2 trunk failover on the switch, the link state of the internal downstream ports are  
bound to the link state of one or more of the external upstream ports. An internal downstream port is an  
interface that is connected to the server. An external upstream port is an interface that is connected to  
the external network. When you associate a set of downstream ports to a set of upstream ports and if all  
of the upstream ports become unavailable, trunk failover automatically puts all of the associated  
downstream ports in an error-disabled state. This causes the server primary interface to failover to the  
secondary interface.  
When Layer 2 trunk failover is not enabled, and if the upstream interfaces lose connectivity, (the external  
switch or router goes down, the cables are disconnected or link is lost), the link state of the downstream  
interfaces remain unchanged. The server is not aware that external connectivity has been lost and does  
not failover to the secondary interface.  
An interface can be an aggregation of ports (an EtherChannel) or a single physical port in access or trunk  
mode. Each downstream interface can be associated with one or more upstream interfaces. Upstream  
interfaces can be bundled together, and each downstream interface can be associated with a single group  
consisting of multiple upstream interfaces. These groups are referred to as link-state groups.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Configuring Layer 2 Trunk Failover  
The link state of the downstream interfaces depend on the link state of the upstream interfaces in the  
associated link-state group. If all of the upstream interfaces in a link-state group are in a link-down state,  
then the associated downstream interfaces are forced into a link-down state. If any one of the upstream  
interfaces in the link-state group is in a link-up state, the associated downstream interfaces are allowed  
to change to, or remain in, a link-up state.  
In Figure 24-4, downstream interfaces 1, 2, and 3 are in link-state group 1 with upstream interfaces 17  
and 18. Similarly, downstream interfaces 4, 5, and 6 are in link-state group 2 with upstream interfaces  
19 and 20.  
If link is lost on upstream interface 17, the link state of downstream interfaces 1 to 3 do not change. If  
upstream interface 18 also loses link, downstream interfaces 1 to 3 go into a link-down state.  
Downstream interfaces 4 to 6 do not change state.  
You can recover a downstream interface link-down condition by removing the failed downstream port  
from the link-state group. You can also enable one of the upstream interfaces in the group to change to  
the link-up state. To recover multiple downstream interfaces, disable the link-state group.  
Figure 24-4  
Typical Layer 2 Trunk Failover Configuration  
Downstream interface 1  
Downstream interface 2  
Downstream interface 3  
Downstream interface 4  
Downstream interface 5  
Downstream interface 6  
Link-state group 1  
Upstream interface 17  
Upstream interface 18  
Link-state group 2  
Upstream interface 19  
Upstream interface 20  
Cisco  
ESM  
Network  
For example  
Catalyst 3550 Switch  
BladeCenter  
Configuring Layer 2 Trunk Failover  
These sections describe how to configure trunk failover ports:  
•
•
•
Default Layer 2 Trunk Failover Configuration, page 24-16  
Layer 2 Trunk Failover Configuration Guidelines, page 24-17  
Configuring Layer 2 Trunk Failover, page 24-17  
Default Layer 2 Trunk Failover Configuration  
There are no link-state groups defined, and trunk failover is not enabled for any group.  
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Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover  
Configuring Layer 2 Trunk Failover  
Layer 2 Trunk Failover Configuration Guidelines  
Follow these guidelines to avoid configuration problems:  
•
Do not configure an internal management module interface (gi0/15 or gi0/16) as a member of a  
link-state group.  
•
•
Do not configure an EtherChannel as a downstream interface.  
An interface that is defined as an upstream interface cannot also be defined as a downstream  
interface in the same or a different link-state group. The reverse is also true.  
•
•
An interface cannot be a member of more than one link-state group.  
You can configure only two link-state groups per switch.  
Configuring Layer 2 Trunk Failover  
Beginning in privileged EXEC mode, follow these steps to configure a link-state group and to assign an  
interface to a group:  
Command  
Purpose  
Step 1  
Step 2  
configure terminal  
Enter global configuration mode.  
link state track number  
Create a link-state group, and enable link-state tracking. The  
group number can be 1 or 2: the default is 1.  
Step 3  
interface interface-id  
Specify a physical interface or range of interfaces to configure,  
and enter interface configuration mode.  
Valid interfaces include physical ports in access or trunk mode  
(IEEE 802.1q) or multiple physical ports bundled into an  
EtherChannel interface (static or LACP), also in trunk mode.  
Step 4  
link state group [number] {upstream |  
downstream}  
Specify a link-state group, and configure the interface as either  
an upstream or downstream interface in the group.  
Step 5  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show running-config  
copy running-config startup-config  
(Optional) Save your entries in the configuration file.  
This example shows how to create a link-state group and to configure the interfaces:  
Switch# configure terminal  
Switch(config)# link state track 1  
Switch(config)# interface range gigabitethernet0/17 -18  
Switch(config-if)# link state group 1 upstream  
Switch(config-if)# interface range gigabitethernet0/1 -8  
Switch(config-if)# link state group 1 downstream  
Switch(config-if)# end  
To disable a link-state group, use the no link state track number global configuration command.  
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Displaying Layer 2 Trunk Failover Status  
Displaying Layer 2 Trunk Failover Status  
Use the show link state group command to display the link-state group information. Enter this  
command without keywords to display information about all link-state groups. Enter the group number  
to display information specific to the group. Enter the detail keyword to display detailed information  
about the group.  
For detailed information about the fields in the display, see the command reference for this release.  
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C H A P T E R  
25  
Troubleshooting  
This chapter describes how to identify and resolve Cisco Systems Intelligent Gigabit Ethernet Switch  
Module software problems related to the Cisco IOS software. Depending on the nature of the problem,  
you can use the command-line interface (CLI), the device manager, or CiscoWorks to identify and solve  
problems.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release and the Cisco IOS Command Summary for Cisco IOS Release 12.1.  
This chapter consists of these sections:  
•
•
•
•
•
•
Using Recovery Procedures, page 25-1  
Preventing Autonegotiation Mismatches, page 25-7  
SFP Module Security and Identification, page 25-7  
Diagnosing Connectivity Problems, page 25-7  
Using Debug Commands, page 25-11  
Using the crashinfo File, page 25-13  
Using Recovery Procedures  
These recovery procedures require that you have physical access to the switch:  
•
•
Recovering from a Software Failure, page 25-1  
Recovering from Lost or Forgotten Passwords, page 25-2  
Recovering from a Software Failure  
Switch software can be corrupted during an upgrade, by downloading the wrong file to the switch, and  
by deleting the image file. In all of these cases, the switch does not pass the power-on self-test (POST),  
and there is no connectivity.  
This procedure uses the Xmodem Protocol to recover from a corrupt or wrong image file. There are many  
software packages that support the Xmodem Protocol, and this procedure is largely dependent on the  
emulation software that you are using.  
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Chapter 25 Troubleshooting  
Using Recovery Procedures  
Follow these steps to recover from a software failure:  
Step 1  
Connect a PC with terminal-emulation software supporting the Xmodem Protocol to the switch service  
port.  
Step 2  
Step 3  
Step 4  
Set the line speed on the emulation software to 9600 baud.  
Power down the switch from the management module.  
Power up the switch from the management module.  
The software image does not load. The switch starts in boot loader mode, which is indicated by the  
switch#prompt.  
Step 5  
Step 6  
Use the boot loader to enter commands, and start the transfer.  
switch# copy xmodem: flash:image_filename.bin  
When the Xmodem request appears, use the appropriate command on the terminal-emulation software  
to start the transfer and to copy the software image to flash memory.  
Recovering from Lost or Forgotten Passwords  
Follow these steps if you have forgotten or lost the switch password on a switch:  
Step 1  
Connect a terminal or PC with terminal emulation software to the service port. For more information,  
see the switch hardware installation guide.  
Note  
You can configure your switch for Telnet by following the procedure in the “Accessing the CLI”  
section on page 2-9.  
Step 2  
Step 3  
Step 4  
Set the line speed on the emulation software to 9600 baud.  
Power down the switch from the management module.  
Power up the switch from the management module and, within 15 seconds, press the Break key from the  
terminal emulation window to force the switch into ROMMON mode.  
Several lines of information about the software appear, as do instructions:  
The system has been interrupted prior to initializing the flash file system. These  
commands will initialize the flash file system, and finish loading the operating system  
software:  
flash_init  
load_helper  
boot  
Step 5  
Step 6  
Initialize the flash file system:  
switch: flash_init  
If you had set the service port speed to anything other than 9600, it has been reset to that particular speed.  
Change the emulation software line speed to match that of the switch service port.  
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Chapter 25 Troubleshooting  
Using Recovery Procedures  
Step 7  
Step 8  
Load any helper files:  
switch: load_helper  
Display the contents of flash memory:  
switch: dir flash:  
The switch file system appears in the directory.  
Rename the configuration file to config.text.old.  
This file contains the password definition.  
Step 9  
switch: rename flash:config.text flash:config.text.old  
Step 10 Boot the system:  
switch: boot  
The switch is set to run on its manufacturing default configuration.  
Step 11 At the switch prompt, change to privileged EXEC mode:  
switch> enable  
Step 12 Rename the configuration file to its original name:  
switch# rename flash:config.text.old flash:config.text  
Step 13 Copy the configuration file into memory:  
switch# copy flash:config.text system:running-config  
Source filename [config.text]?  
Destination filename [running-config]?  
Press Return in response to the confirmation prompts.  
The configuration file is now reloaded, and you can use the following normal commands to change the  
password.  
Step 14 Enter global configuration mode:  
switch# configure terminal  
Step 15 Change the password:  
switch(config)# enable secret <password>  
or  
switch(config)# enable password <password>  
Step 16 Return to privileged EXEC mode:  
switch(config)# exit  
switch#  
Step 17 Write the running configuration to the startup configuration file:  
switch# copy running-config startup-config  
The new password is now included in the startup configuration.  
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Chapter 25 Troubleshooting  
Using Recovery Procedures  
Password Recovery with Password Recovery Enabled  
If the password-recovery mechanism is enabled, this message appears:  
The system has been interrupted prior to initializing the flash file system. The following  
commands will initialize the flash file system, and finish loading the operating system  
software:  
flash_init  
load_helper  
boot  
Follow these steps when the password-recovery is enabled:  
Step 1  
Initialize the flash file system:  
switch: flash_init  
Step 2  
Step 3  
If you had set the serviceport speed to anything other than 9600, it has been reset to that particular speed.  
Change the emulation software line speed to match that of the switch serviceport.  
Load any helper files:  
switch: load_helper  
Step 4  
Step 5  
Step 6  
Display the contents of flash memory:  
switch: dir flash:  
The switch file system appears in the directory.  
Rename the configuration file to config.text.old.  
This file contains the password definition.  
switch: rename flash:config.text flash:config.text.old  
Boot the system:  
switch: boot  
The switch is set to run on its manufacturing default configuration.  
At the switch prompt, enter privileged EXEC mode:  
Switch> enable  
Step 7  
Step 8  
Step 9  
Rename the configuration file to its original name:  
Switch# rename flash:config.text.old flash:config.text  
Copy the configuration file into memory:  
Switch# copy flash:config.text system:running-config  
Source filename [config.text]?  
Destination filename [running-config]?  
Press Return in response to the confirmation prompts.  
The configuration file is now reloaded, and you can change the password.  
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Chapter 25 Troubleshooting  
Using Recovery Procedures  
Step 10 Enter global configuration mode:  
Switch# configure terminal  
Step 11 Change the password:  
Switch (config)# enable secret password  
The secret password can be from 1 to 25 alphanumeric characters, can start with a number, is case  
sensitive, and allows spaces but ignores leading spaces.  
Step 12 Return to privileged EXEC mode:  
Switch (config)# exit  
Switch#  
Step 13 Write the running configuration to the startup configuration file:  
Switch# copy running-config startup-config  
The new password is now in the startup configuration.  
Note  
This procedure is likely to leave your switch VLAN interface in a shutdown state. You can see  
which interface is in this state by entering the show running-config privileged EXEC command.  
To re-enable the interface, enter the interface vlan vlan-id global configuration command, and  
specify the VLAN ID of the shutdown interface. With the switch in interface configuration  
mode, enter the no shutdown command.  
Procedure with Password Recovery Disabled  
If the password-recovery mechanism is disabled, this message appears:  
The password-recovery mechanism has been triggered, but  
is currently disabled. Access to the boot loader prompt  
through the password-recovery mechanism is disallowed at  
this point. However, if you agree to let the system be  
reset back to the default system configuration, access  
to the boot loader prompt can still be allowed.  
Would you like to reset the system back to the default configuration (y/n)?  
Caution  
Returning the switch to the default configuration results in the loss of all existing configurations. We  
recommend that you contact your system administrator to verify if there are backup switch and VLAN  
configuration files.  
•
If you enter n (no), the normal boot process continues as if the Mode button had not been pressed;  
you cannot access the boot loader prompt, and you cannot enter a new password. You see the  
message:  
Press Enter to continue........  
•
If you enter y (yes), the configuration file in flash memory and the VLAN database file are deleted.  
When the default configuration loads, you can reset the password.  
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Chapter 25 Troubleshooting  
Using Recovery Procedures  
Follow these steps when the password-recovery mechanism is disabled:  
Elect to continue with password recovery and lose the existing configuration:  
Step 1  
Step 2  
Step 3  
Would you like to reset the system back to the default configuration (y/n)? Y  
Load any helper files:  
Switch: load_helper  
Display the contents of flash memory:  
switch: dir flash:  
The switch file system appears in the directory.  
Boot the system:  
Step 4  
Switch: boot  
You are prompted to start the setup program. To continue with password recovery, enter N at the prompt:  
Continue with the configuration dialog? [yes/no]: N  
Step 5  
Step 6  
Step 7  
At the switch prompt, enter privileged EXEC mode:  
Switch> enable  
Enter global configuration mode:  
Switch# configure terminal  
Change the password:  
Switch (config)# enable secret password  
The secret password can be from 1 to 25 alphanumeric characters, can start with a number, is case  
sensitive, and allows spaces but ignores leading spaces.  
Step 8  
Step 9  
Return to privileged EXEC mode:  
Switch (config)# exit  
Switch#  
Write the running configuration to the startup configuration file:  
Switch# copy running-config startup-config  
The new password is now in the startup configuration.  
Note  
This procedure is likely to leave your switch VLAN interface in a shutdown state. You can see  
which interface is in this state by entering the show running-config privileged EXEC command.  
To re-enable the interface, enter the interface vlan vlan-id global configuration command, and  
specify the VLAN ID of the shutdown interface. With the switch in interface configuration  
mode, enter the no shutdown command.  
Step 10 You must now reconfigure the switch. If the system administrator has the backup switch and VLAN  
configuration files available, you should use those.  
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Chapter 25 Troubleshooting  
Preventing Autonegotiation Mismatches  
Preventing Autonegotiation Mismatches  
The IEEE 802.3ab autonegotiation protocol manages the switch settings for speed (10 Mbps, 100 Mbps,  
and 1000 Mbps) and duplex (half or full). There are situations when this protocol can incorrectly align  
these settings, reducing performance. A mismatch occurs under these circumstances:  
•
A manually set speed or duplex parameter is different from the manually set speed or duplex  
parameter on the connected port.  
•
A port is set to autonegotiate, and the connected port is set to full duplex with no autonegotiation.  
To maximize switch performance and ensure a link, follow one of these guidelines when changing the  
settings for duplex and speed:  
•
•
Let both ports autonegotiate both speed and duplex.  
Manually set the speed and duplex parameters for the ports on both ends of the connection.  
Note  
If a remote device does not autonegotiate, configure the duplex settings on the two ports to match. The  
speed parameter can adjust itself even if the connected port does not autonegotiate.  
SFP Module Security and Identification  
Small form-factor pluggable (SFP) modules have a serial EEPROM that contains the module serial  
number, the vendor name and ID, a unique security code, and cyclic redundancy check (CRC). When an  
SFP module is inserted in the switch, the switch software reads the EEPROM to check the serial number,  
vendor name and vendor ID, and recompute the security code and CRC. If the serial number, the vendor  
name or vendor ID, the security code, or CRC is invalid, the switch places the interface in an  
error-disabled state.  
Note  
If you are using a non-Cisco SFP module, remove the SFP module from the switch, and replace it with  
a Cisco module.  
After inserting a Cisco SFP module, use the errdisable recovery cause gbic-invalid global  
configuration command to verify the port status, and enter a time interval for recovering from the  
error-disabled state. After the elapsed interval, the switch brings the interface out of the error-disabled  
state and retries the operation. For more information about the errdisable recovery command, see the  
command reference for this release.  
Diagnosing Connectivity Problems  
This section describes how to troubleshoot connectivity problems:  
Using Ping, page 25-8  
Using Layer 2 Traceroute, page 25-9  
•
•
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Chapter 25 Troubleshooting  
Diagnosing Connectivity Problems  
Using Ping  
This section consists of this information:  
•
•
Understanding Ping, page 25-8  
Executing Ping, page 25-8  
Understanding Ping  
The switch supports IP ping, which you can use to test connectivity to remote hosts. Ping sends an echo  
request packet to an address and waits for a reply. Ping returns one of these responses:  
•
Normal response—The normal response (hostname is alive) occurs in 1 to 10 seconds, depending  
on network traffic.  
•
•
•
Destination does not respond—If the host does not respond, a no-answer message is returned.  
Unknown host—If the host does not exist, an unknown host message is returned.  
Destination unreachable—If the default gateway cannot reach the specified network, a  
destination-unreachable message is returned.  
•
Network or host unreachable—If there is no entry in the route table for the host or network, a  
network or host unreachable message is returned.  
Executing Ping  
If you attempt to ping a host in a different IP subnetwork, you must define a static route to the network.  
Beginning in privileged EXEC mode, use this command to ping another device on the network from the  
switch:  
Command  
Purpose  
ping [ip] {host | address}  
Ping a remote host through IP or by supplying the host name or  
network address.  
Note  
Though other protocol keywords are available with the ping command, they are not supported in this  
release.  
This example shows how to ping an IP host:  
Switch# ping 172.20.52.3  
Type escape sequence to abort.  
Sending 5, 100-byte ICMP Echoes to 172.20.52.3, timeout is 2 seconds:  
!!!!!  
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms  
Switch#  
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Chapter 25 Troubleshooting  
Diagnosing Connectivity Problems  
Table 25-1 describes the possible ping character output.  
Table 25-1  
Ping Output Display Characters  
Character  
Description  
!
Each exclamation point means receipt of a reply.  
.
Each period means the network server timed out while waiting for a reply.  
A destination unreachable error PDU was received.  
A congestion experienced packet was received.  
User interrupted test.  
U
C
I
?
Unknown packet type.  
&
Packet lifetime exceeded.  
To terminate a ping session, enter the escape sequence (Ctrl-^ X by default). You enter the default by  
simultaneously pressing and releasing the Ctrl, Shift, and 6 keys, and then pressing the X key.  
Using Layer 2 Traceroute  
This section describes this information:  
•
•
•
Understanding Layer 2 Traceroute, page 25-9  
Usage Guidelines, page 25-9  
Displaying the Physical Path, page 25-10  
Understanding Layer 2 Traceroute  
The Layer 2 traceroute feature allows the switch to identify the physical path that a packet takes from a  
source device to a destination device. Layer 2 traceroute supports only unicast source and destination  
MAC addresses. It determines the path by using the MAC address tables of the switches in the path.  
When the switch detects a device in the path that does not support Layer 2 traceroute, the switch  
continues to send Layer 2 trace queries and lets them time out.  
The switch can only identify the path from the source device to the destination device. It cannot identify  
the path that a packet takes from source host to the source device or from the destination device to the  
destination host.  
Usage Guidelines  
These are the Layer 2 traceroute usage guidelines:  
•
Cisco Discovery Protocol (CDP) must be enabled on all the devices in the network. For Layer 2  
traceroute to functional properly, do not disable CDP. If any devices in the physical path are  
transparent to CDP, the switch cannot identify the path through these devices.  
Note  
For more information about enabling CDP, see Chapter 17, “Configuring CDP.”  
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Chapter 25 Troubleshooting  
Diagnosing Connectivity Problems  
•
A switch is reachable from another switch when you can test connectivity by using the ping  
privileged EXEC command. All switches in the physical path must be reachable from each other.  
•
•
The maximum number of hops identified in the path is ten.  
You can enter the traceroute mac or the traceroute mac ip privileged EXEC command on a switch  
that is not in the physical path from the source device to the destination device. All switches in the  
path must be reachable from this switch.  
•
The traceroute mac command output shows the Layer 2 path only when the specified source and  
destination MAC addresses belong to the same VLAN. If you specify source and destination MAC  
addresses that belong to different VLANs, the Layer 2 path is not identified, and an error message  
appears.  
•
•
If you specify a multicast source or destination MAC address, the path is not identified, and an error  
message appears.  
If the source or destination MAC address belongs to multiple VLANs, you must specify the VLAN  
to which both the source and destination MAC addresses belong. If the VLAN is not specified, the  
path is not identified, and an error message appears.  
•
The traceroute mac ip command output shows the Layer 2 path when the specified source and  
destination IP addresses belong to the same subnet. When you specify the IP addresses, the switch  
uses Address Resolution Protocol (ARP) to associate the IP addresses with the corresponding MAC  
addresses and the VLAN IDs.  
–
If an ARP entry exists for the specified IP address, the switch uses the associated MAC address  
and identifies the physical path.  
–
If an ARP entry does not exist, the switch sends an ARP query and tries to resolve the IP  
address. If the IP address is not resolved, the path is not identified, and an error message  
appears.  
•
•
When multiple devices are attached to one port through hubs (for example, multiple CDP neighbors  
are detected on a port), the Layer 2 traceroute feature is not supported. When more than one CDP  
neighbor is detected on a port, the Layer 2 path is not identified, and an error message appears.  
This feature is not supported in Token Ring VLANs.  
Displaying the Physical Path  
You can display physical path that a packet takes from a source device to a destination device by using  
one of these privileged EXEC commands:  
•
traceroute mac [interface interface-id] {source-mac-address} [interface interface-id]  
{destination-mac-address} [vlan vlan-id] [detail]  
•
traceroute mac ip {source-ip-address | source-hostname} {destination-ip-address |  
destination-hostname} [detail]  
For more information, see the command reference for this release.  
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Chapter 25 Troubleshooting  
Using Debug Commands  
Using Debug Commands  
This section explains how you use the debug commands to diagnose and resolve internetworking  
problems. It contains this information:  
•
•
•
•
Enabling Debugging on a Specific Feature, page 25-11  
Enabling All-System Diagnostics, page 25-12  
Redirecting Debug and Error Message Output, page 25-12  
Using the debug auto qos Command, page 25-12  
Caution  
Because debugging output is assigned high priority in the CPU process, it can render the system  
unusable. For this reason, use debug commands only to troubleshoot specific problems or during  
troubleshooting sessions with technical support staff. It is best to use debug commands during periods  
of lower network traffic and fewer users. Debugging during these periods decreases the likelihood that  
increased debug command processing overhead will affect system use.  
Note  
For complete syntax and usage information for specific debug commands, see the command reference  
for this release.  
Enabling Debugging on a Specific Feature  
All debug commands are entered in privileged EXEC mode, and most debug commands take no  
arguments. For example, beginning in privileged EXEC mode, enter this command to enable the  
debugging for EtherChannel:  
Switch# debug etherchannel  
The switch continues to generate output until you enter the no form of the command.  
If you enable a debug command and no output appears, consider these possibilities:  
•
The switch might not be properly configured to generate the type of traffic that you want to monitor.  
Use the show running-config command to verify the configuration.  
•
Even if the switch is properly configured, it might not generate the type of traffic that you want to  
monitor during the particular period that debugging is enabled. Depending on the feature you are  
debugging, you can use commands such as the TCP/IP ping command to generate network traffic.  
To disable debugging of EtherChannel, enter this command in privileged EXEC mode:  
Switch# no debug etherchannel  
Alternately, in privileged EXEC mode, you can enter the undebug form of the command:  
Switch# undebug etherchannel  
To display the state of each debugging option, enter this command in privileged EXEC mode:  
Switch# show debugging  
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Chapter 25 Troubleshooting  
Using Debug Commands  
Enabling All-System Diagnostics  
Beginning in privileged EXEC mode, enter this command to enable all-system diagnostics:  
Switch# debug all  
Caution  
Because debugging output takes priority over other network traffic, and because the debug all privileged  
EXEC command generates more output than any other debug command, it can severely diminish switch  
performance or even render it unusable. In virtually all cases, it is best to use more specific debug  
commands.  
The no debug all privileged EXEC command disables all diagnostic output. Using the no debug all  
command is a convenient way to ensure that you have not accidentally left any debug commands  
enabled.  
Redirecting Debug and Error Message Output  
By default, the network server sends the output from debug commands and system error messages to the  
console. If you use this default, you can use a virtual terminal connection to monitor debug output  
instead of connecting to the serviceport.  
Possible destinations include the console, virtual terminals, internal buffer, and UNIX hosts running a  
syslog server. The syslog format is compatible with 4.3 Berkeley Standard Distribution (BSD) UNIX  
and its derivatives.  
Note  
Be aware that the debugging destination you use affects system overhead. Logging messages to the  
console produces very high overhead, whereas logging messages to a virtual terminal produces less  
overhead. Logging messages to a syslog server produces even less, and logging to an internal buffer  
produces the least overhead of any method.  
For more information about system message logging, see Chapter 20, “Configuring System Message  
Logging.”  
Using the debug auto qos Command  
You can use the debug auto qos privileged EXEC command to display quality of service (QoS)  
commands that are automatically generated when automatic-QoS (auto-QoS) is enabled.  
Beginning in privileged EXEC mode, follow these steps to display the QoS commands and enable  
auto-QoS for voice over IP (VoIP) within a QoS domain:  
Command  
Purpose  
Step 1  
Step 2  
debug auto qos  
Enable debugging for auto-QoS. When debugging is enabled, the  
switch displays the QoS commands that are automatically generated  
when auto-QoS is enabled or disabled.  
configure terminal  
Enter global configuration mode.  
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Chapter 25 Troubleshooting  
Using the crashinfo File  
Command  
Purpose  
Step 3  
interface interface-id  
Specify the interface that is connected to a Cisco IP Phone, and enter  
interface configuration mode. You also can specify the uplink interface  
that is connected to another switch or router in the interior of the  
network.  
Step 4  
auto qos voip {cisco-phone | trust}  
Enable auto-QoS.  
The keywords have these meanings:  
•
cisco-phone—If the interface is connected to a Cisco IP Phone,  
the QoS labels of incoming packets are trusted only when the IP  
phone is detected.  
•
trust—The uplink interface is connected to a trusted switch or  
router, and the VoIP classification in the ingress packet is trusted.  
Step 5  
Step 6  
end  
Return to privileged EXEC mode.  
Verify your entries.  
show auto qos interface interface-id  
This command displays the auto-QoS configuration that was initially  
applied; it does not display any user changes to the configuration that  
might be in effect.  
For more information about auto-QoS, see the “Configuring Auto-QoS” section on page 23-9.  
This example shows how to display the QoS commands that are automatically generated when auto-QoS  
is enabled:  
Switch# debug auto qos  
AutoQoS debugging is on  
Switch# configure terminal  
Enter configuration commands, one per line. End with CNTL/Z.  
Switch(config)# interface gigabitethernet0/17  
Switch(config-if)# auto qos voip cisco-phone  
Using the crashinfo File  
The crashinfo file saves information that helps technical support representatives to debug problems that  
caused the software image to fail (crash). The switch writes the crash information to the console at the  
time of the failure, and the file is created the next time you boot the image after the failure (instead of  
while the system is failing).  
The information in the file includes the software image name and version that failed, a dump of the  
processor registers, and a stack trace. You can give this information to the technical support  
representative by using the show tech-support privileged EXEC command.  
All crashinfo files are kept in this directory on the flash file system:  
flash:/crashinfo/crashinfo_n where n is a sequence number.  
Each new crashinfo file that is created uses a sequence number that is larger than any previously existing  
sequence number, so the file with the largest sequence number describes the most recent failure. Version  
numbers are used instead of a timestamp because the switches do not include a real-time clock. You  
cannot change the name of the file that the system will use when it creates the file. However, after the  
file is created, you can use the rename privileged EXEC command to rename it, but the contents of the  
renamed file will not be displayed by the show stacks or the show tech-support privileged EXEC  
command. You can delete crashinfo files by using the delete privileged EXEC command.  
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Chapter 25 Troubleshooting  
Using the crashinfo File  
You can display the most recent crashinfo file (that is, the file with the highest sequence number at the  
end of its filename) by entering the show stacks or the show tech-support privileged EXEC command.  
You also can access the file by using any command that can copy or display files, such as the more or  
the copy privileged EXEC command.  
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A P P E N D I X  
A
Supported MIBs  
This appendix lists the supported MIBs for this release of the Cisco Systems Intelligent Gigabit Ethernet  
Switch Module. It contains these sections:  
•
•
MIB List, page A-1  
Using FTP to Access the MIB Files, page A-3  
MIB List  
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
BRIDGE-MIB (RFC1493)  
CISCO-2900-MIB  
CISCO-BULK-FILE-MIB  
CISCO-CDP-MIB  
CISCO_CONFIG_COPY_MIB  
CISCO-CONFIG-MAN-MIB  
CISCO-ENTITY-MIB  
CISCO-ENTITY-VENDORTYPE-OID-MIB  
CISCO_ENVMON_MIB  
CISCO-FLASH-MIB  
CISCO-FTP-CLIENT-MIB  
CISCO-IGMP-FILTER-MIB  
CISCO-IMAGE-MIB  
CISCO-MAC-NOTIFICATION-MIB  
CISCO-MEMORY-POOL-MIB  
CISCO-PAE-MIB  
CISCO-PAGP-MIB  
CISCO-PING-MIB  
CISCO-PORT-SECURITY-MIB  
CISCO-PROCESS-MIB  
CISCO-PRODUCTS-MIB  
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Appendix A Supported MIBs  
MIB List  
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
CISCO-RTTMON-MIB (subsystems supported: sub_rtt_rmon and sub_rtt_rmonlib)  
CISCO-SMI  
CISCO_STACKMAKER_MIB  
CISCO-STP-EXTENSIONS-MIB  
CISCO-SYSLOG-MIB  
CISCO-TC  
CISCO-TCP-MIB  
CISCO-VLAN-MEMBERSHIP-MIB  
CISCO-VTP-MIB  
ENTITY-MIB  
IEEE8021-PAE-MIB  
IANAifType-MIB  
IF-MIB (RFC 1573)  
OLD-CISCO-CHASSIS-MIB  
OLD-CISCO-CPU-MIB  
OLD-CISCO-INTERFACES-MIB  
OLD-CISCO-IP-MIB  
OLD-CISCO-MEMORY-MIB  
OLD-CISCO-SYSTEM-MIB  
OLD-CISCO-TCP-MIB  
OLD-CISCO-TS-MIB  
RFC1213-MIB  
RFC1398-MIB  
RMON-MIB (RFC 1757)  
RS-232-MIB  
SNMPv2-MIB  
SNMPv2-SMI  
SNMPv2-TC  
TCP-MIB  
UDP-MIB  
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Appendix A Supported MIBs  
Using FTP to Access the MIB Files  
Using FTP to Access the MIB Files  
To access the Management Information Base (MIBs) for the Cisco Systems Intelligent Gigabit Ethernet  
Switch Module, follow these steps:  
1. Go to the IBM web site:  
http://www.ibm.com/support.  
2. Click Support & downloads > Downloads and drivers > BladeCenter (Blades) > BladeCenter  
chassis Hardware only > Firmware.  
3. Click Cisco Systems Intelligent Gigabit Ethernet Switch Module Firmware update - IBM  
BladeCenter.  
4. Find and click the MIBs link.  
5. Click Download now to save the file to your computer.  
6. Use PKUNZIP to expand the files on your computer.  
7. From your computer you can ftp the files to your switch.  
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Using FTP to Access the MIB Files  
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A P P E N D I X  
B
Working with the Cisco IOS File System,  
Configuration Files, and Software Images  
This appendix describes how to manipulate the Cisco Systems Intelligent Gigabit Ethernet Switch  
Module flash file system, how to copy configuration files, and how to archive (upload and download)  
software images.  
Note  
For complete syntax and usage information for the commands used in this chapter, see the command  
reference for this release and the Cisco IOS Configuration Fundamentals Command Reference,  
Release 12.1.  
This appendix consists of these sections:  
•
•
•
Working with the Flash File System, page B-1  
Working with Configuration Files, page B-8  
Working with Software Images, page B-19  
Working with the Flash File System  
The flash file system on your switch provides several commands to help you manage software image and  
configuration files.  
The flash file system is a single flash device on which you can store files. This flash device is called  
flash:.  
This section contains this information:  
•
•
•
•
•
•
•
•
Displaying Available File Systems, page B-2  
Setting the Default File System, page B-3  
Displaying Information about Files on a File System, page B-3  
Creating and Removing Directories, page B-4  
Copying Files, page B-5  
Deleting Files, page B-6  
Creating, Displaying, and Extracting tar Files, page B-6  
Displaying the Contents of a File, page B-8  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with the Flash File System  
Displaying Available File Systems  
To display the available file systems on your switch, use the show file systems privileged EXEC  
command as shown in this example:  
Switch# show file systems  
File Systems:  
Size(b)  
Free(b)  
Type Flags Prefixes  
*
16128000  
16128000  
11118592  
11118592  
flash  
unknown  
nvram  
network  
opaque  
opaque  
opaque  
opaque  
network  
network  
rw  
rw  
rw  
rw  
rw  
rw  
ro  
ro  
rw  
rw  
flash:  
zflash:  
nvram:  
tftp:  
32768  
26363  
-
-
-
-
-
-
-
-
-
-
-
-
-
-
null:  
system:  
xmodem:  
ymodem:  
rcp:  
ftp:  
Table B-1  
show file systems Field Descriptions  
Value  
Field  
Size(b)  
Free(b)  
Type  
Amount of memory in the file system in bytes.  
Amount of free memory in the file system in bytes.  
Type of file system.  
flash—The file system is for a flash memory device.  
nvram—The file system is for an NVRAM device.  
opaque—The file system is a locally generated pseudo file system (for example, the system) or a download  
interface, such as brimux.  
unknown—The file system is an unknown type.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with the Flash File System  
Table B-1  
show file systems Field Descriptions (continued)  
Value  
Field  
Flags  
Permission for file system.  
ro—read-only.  
rw—read/write.  
wo—write-only.  
Prefixes  
Alias for file system.  
bs:—Read-only file system; stores the boot loader image.  
vb:—Stores the boot environment variables.  
flash:—Flash file system.  
nvram:—NVRAM.  
null:—Null destination for copies. You can copy a remote file to null to determine its size.  
rcp:—Remote Copy Protocol (RCP) network server.  
system:—Contains the system memory, including the running configuration.  
tftp:—TFTP network server.  
xmodem:—Obtain the file from a network machine by using the Xmodem protocol.  
ymodem:—Obtain the file from a network machine by using the Ymodem protocol.  
zflash:—Read-only file decompression file system, which mirrors the contents of the flash file system.  
Setting the Default File System  
You can specify the file system or directory that the system uses as the default file system by using the  
cd filesystem: privileged EXEC command. You can set the default file system to omit the filesystem:  
argument from related commands. For example, for all privileged EXEC commands that have the  
optional filesystem: argument, the system uses the file system specified by the cd command.  
By default, the default file system is flash:.  
You can display the current default file system as specified by the cd command by using the pwd  
privileged EXEC command.  
Displaying Information about Files on a File System  
You can view a list of the contents of a file system before manipulating its contents. For example, before  
copying a new configuration file to flash memory, you might want to verify that the file system does not  
already contain a configuration file with the same name. Similarly, before copying a flash configuration  
file to another location, you might want to verify its filename for use in another command.  
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Working with the Flash File System  
To display information about files on a file system, use one of the privileged EXEC commands in  
Table B-2:  
Table B-2  
Commands for Displaying Information About Files  
Command  
Description  
dir [/all] [filesystem:][filename]  
show file systems  
Display a list of files on a file system.  
Display more information about each of the files on a file system.  
Display information about a specific file.  
show file information file-url  
show file descriptors  
Display a list of open file descriptors. File descriptors are the internal representations  
of open files. You can use this command to see if another user has a file open.  
Changing Directories and Displaying the Working Directory  
Beginning in privileged EXEC mode, follow these steps to change directories and display the working  
directory.  
Command  
Purpose  
Step 1  
Step 2  
dir filesystem:  
Display the directories on the specified file system.  
For filesystem:, use flash: for the system board flash device.  
Change to the directory of interest.  
cd new_configs  
pwd  
The command example shows how to change to the directory named  
new_configs.  
Step 3  
Display the working directory.  
Creating and Removing Directories  
Beginning in privileged EXEC mode, follow these steps to create and remove a directory:  
Command  
Purpose  
Step 1  
Step 2  
dir filesystem:  
Display the directories on the specified file system.  
For filesystem:, use flash: for the system board flash device.  
Create a new directory.  
mkdir old_configs  
The command example shows how to create the directory named old_configs.  
Directory names are case sensitive.  
Directory names are limited to 45 characters between the slashes (/); the name  
cannot contain control characters, spaces, deletes, slashes, quotes, semicolons,  
or colons.  
Step 3  
dir filesystem:  
Verify your entry.  
To delete a directory with all its files and subdirectories, use the delete /force /recursive  
filesystem:/file-url privileged EXEC command.  
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Working with the Flash File System  
Use the /recursive keyword to delete the named directory and all subdirectories and the files contained  
in it. Use the /force keyword to suppress the prompting that confirms a deletion of each file in the  
directory. You are prompted only once at the beginning of this deletion process. Use the /force and  
/recursive keywords for deleting old software images that were installed by using the archive  
download-sw command but are no longer needed.  
For filesystem, use flash: for the system board flash device. For file-url, enter the name of the directory  
to be deleted. All the files in the directory and the directory are removed.  
Caution  
When files and directories are deleted, their contents cannot be recovered.  
Copying Files  
To copy a file from a source to a destination, use the copy [/erase] source-url destination-url privileged  
EXEC command. For the source and destination URLs, you can use running-config and startup-config  
keyword shortcuts. For example, the copy running-config startup-config command saves the currently  
running configuration file to the NVRAM section of flash memory to be used as the configuration during  
system initialization.  
You can also copy to and from special file systems (xmodem:, ymodem:) as the source or destination  
for the file from a network machine that uses the Xmodem or Ymodem protocol.  
Network file system URLs include ftp:, rcp:, and tftp: and have these syntaxes:  
FTP—ftp:[[//username [:password]@location]/directory]/filename  
Remote Copy Protocol (RCP)—rcp:[[//username@location]/directory]/filename  
TFTP—tftp:[[//location]/directory]/filename  
Local writable file systems include flash:.  
Some invalid combinations of source and destination exist. Specifically, you cannot copy these  
combinations:  
•
•
•
From a running configuration to a running configuration  
From a startup configuration to a startup configuration  
From a device to the same device (for example, the copy flash: flash: command is invalid)  
For specific examples of using the copy command with configuration files, see the “Working with  
Configuration Files” section on page B-8.  
To copy software images either by downloading a new version or uploading the existing one, use the  
archive download-sw or the archive upload-sw privileged EXEC command. For more information, see  
the “Working with Software Images” section on page B-19.  
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Working with the Flash File System  
Deleting Files  
When you no longer need a file on a flash memory device, you can permanently delete it. To delete a file  
or directory from a specified flash device, use the delete [/force] [/recursive] [filesystem:]/file-url  
privileged EXEC command.  
Use the /recursive keyword for deleting a directory and all subdirectories and the files contained in it.  
Use the /force keyword to suppress the prompting that confirms a deletion of each file in the directory.  
You are prompted only once at the beginning of this deletion process. Use the /force and /recursive  
keywords for deleting old software images that were installed by using the archive download-sw  
command but are no longer needed.  
If you omit the filesystem: option, the switch uses the default device specified by the cd command. For  
file-url, you specify the path (directory) and the name of the file to be deleted.  
If you attempt to delete the file specified by the CONFIG_FILE or BOOT environment variable, the  
system prompts you to confirm the deletion. If you attempt to delete the last valid system image specified  
in the BOOT environment variable, the system prompts you to confirm the deletion.  
Caution  
When files are deleted, their contents cannot be recovered.  
This example shows how to delete the file myconfig from the default flash memory device:  
Switch# delete myconfig  
Creating, Displaying, and Extracting tar Files  
You can create a tar file and write files into it, list the files in a tar file, and extract the files from a tar  
file as described in the next sections.  
Creating a tar File  
To create a tar file and write files into it, use the privileged EXEC command:  
archive tar /create destination-url flash:/file-url  
For destination-url, specify the destination URL alias for the local or network file system and the name  
of the tar file to create. These options are supported:  
•
For the local flash file system, the syntax is  
flash:  
•
•
•
For the FTP, the syntax is ftp:[[//username[:password]@location]/directory]/tar-filename.tar  
For the RCP, the syntax is rcp:[[//username@location]/directory]/tar-filename.tar  
For the TFTP, the syntax is tftp:[[//location]/directory]/tar-filename.tar  
The tar-filename.tar is the tar file to be created.  
For flash:/file-url, specify the location on the local flash file system from which the new tar file is  
created. You can also specify an optional list of files or directories within the source directory to write  
to the new tar file. If none are specified, all files and directories at this level are written to the newly  
created tar file.  
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Working with the Flash File System  
This example shows how to create a tar file. This command writes the contents of the new-configs  
directory on the local flash device to a file named saved.tar on the TFTP server at 172.20.10.30:  
Switch# archive tar /create tftp:172.20.10.30/saved.tar flash:/new-configs  
Displaying the Contents of a tar File  
To display the contents of a tar file on the screen, use this privileged EXEC command:  
archive tar /table source-url  
For source-url, specify the source URL alias for the local or network file system. These options are  
supported:  
•
For the local flash file system, the syntax is  
flash:  
•
•
•
For the FTP, the syntax is ftp:[[//username[:password]@location]/directory]/tar-filename.tar  
For the RCP, the syntax is rcp:[[//username@location]/directory]/tar-filename.tar  
For the TFTP, the syntax is tftp:[[//location]/directory]/tar-filename.tar  
The tar-filename.tar is the tar file to display.  
You can also limit the display of the files by specifying an optional list of files or directories after the  
tar file; then only these files are displayed. If none are specified, all files and directories are displayed.  
This example shows how to display the contents of the cigesm-i6q4l2-mz.121- 21.EA1.tar file that is in  
flash memory:  
Switch#archive tar /table flash:cigesm-i6q4l2-mz.121-21.EA1.tar  
info (219 bytes)  
cigesm-i6q4l2-mz.121-21.EA1/(directory)  
cigesm-i6q4l2-mz.121-21.EA1/html/(directory)  
cigesm-i6q4l2-mz.121-21.EA1/html/foo.html (0 bytes)  
cigesm-i6q4l2-mz.121-21.EA1/cigesm-i6q4l2-mz.121-21.EA1.bin (610856 bytes)  
cigesm-i6q4l2-mz.121-21.EA1/info (219 bytes)  
info.ver (219 bytes)  
This example shows how to display only the cigesm-i6q4l2-mz.121-21.EA1/html directory and its  
contents:  
Switch#archive tar /table flash:cigesm-i6q4l2-mz.121-21.EA1/html  
cigesm-i6q4l2-mz.121-21.EA1/html/(directory)  
cigesm-i6q4l2-mz.121-21.EA1/html/foo.html (0 bytes)  
Extracting a tar File  
To extract a tar file into a directory on the flash file system, use the privileged EXEC command:  
archive tar /xtract source-url flash:/file-url [dir/file...]  
For source-url, specify the source URL alias for the local file system. These options are supported:  
•
For the local flash file system, the syntax is  
flash:  
•
•
•
For the FTP, the syntax is ftp:[[//username[:password]@location]/directory]/tar-filename.tar  
For the RCP, the syntax is rcp:[[//username@location]/directory]/tar-filename.tar  
For the TFTP, the syntax is tftp:[[//location]/directory]/tar-filename.tar  
The tar-filename.tar is the tar file from which to extract files.  
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Working with Configuration Files  
For flash:/file-url [dir/file...], specify the location on the local flash file system into which the tar file is  
extracted. Use the dir/file... option to specify an optional list of files or directories within the tar file to  
be extracted. If none are specified, all files and directories are extracted.  
This example shows how to extract the contents of a tar file located on the TFTP server at 172.20.10.30.  
This command extracts just the new-configs directory into the root directory on the local flash file  
system. The remaining files in the saved.tar file are ignored.  
Switch# archive tar /xtract tftp:/172.20.10.30/saved.tar flash:/new-configs  
Displaying the Contents of a File  
To display the contents of any readable file, including a file on a remote file system, use the more [/ascii  
| /binary | /ebcdic] file-url privileged EXEC command:  
This example shows how to display the contents of a configuration file on a TFTP server:  
Switch# more tftp://serverA/hampton/savedconfig  
!
! Saved configuration on server  
!
version 11.3  
service timestamps log datetime localtime  
service linenumber  
service udp-small-servers  
service pt-vty-logging  
!
<output truncated>  
Working with Configuration Files  
You can copy (download) configuration files from a TFTP, FTP, or RCP server to the running  
configuration or startup configuration of the switch. You might want to perform this for one of these  
reasons:  
•
•
To restore a backed-up configuration file.  
To use the configuration file for another switch. For example, you might add another switch to your  
network and want it to have a configuration similar to the original switch. By copying the file to the  
new switch, you can change the relevant parts rather than recreating the whole file.  
•
To load the same configuration commands on all the switches in your network so that all the  
switches have similar configurations.  
You can copy (upload) configuration files from the switch to a file server by using TFTP, FTP, or RCP.  
You might perform this task to back up a current configuration file to a server before changing its  
contents so that you can later restore the original configuration file from the server.  
The protocol that you use depends on which type of server you are using. The FTP and RCP transport  
mechanisms provide faster performance and more reliable delivery of data than TFTP. These  
improvements are possible because FTP and RCP are built on and use the TCP/IP stack, which is  
connection-oriented.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
This section includes this information:  
•
•
•
•
•
•
•
Guidelines for Creating and Using Configuration Files, page B-9  
Configuration File Types and Location, page B-10  
Creating a Configuration File By Using a Text Editor, page B-10  
Copying Configuration Files By Using TFTP, page B-10  
Copying Configuration Files By Using FTP, page B-12  
Copying Configuration Files By Using RCP, page B-15  
Clearing Configuration Information, page B-19  
Guidelines for Creating and Using Configuration Files  
Creating configuration files can aid in your switch configuration. Configuration files can contain some  
or all of the commands needed to configure one or more switches. For example, you might want to  
download the same configuration file to several switches that have the same hardware configuration.  
Use these guidelines when creating a configuration file:  
•
•
•
We recommend that you connect through the service port when using configuration files to  
configure the switch. If you configure the switch from a Telnet session, IP addresses are not  
changed, and ports and modules are not disabled.  
If no passwords have been set on the switch, you must set them on each switch by entering the  
enable secret secret-password global configuration command. Enter a blank line for this command.  
The password is saved in the configuration file as clear text.  
If passwords already exist, you cannot enter the enable secret secret-password global configuration  
command in the file because the password verification will fail. If you enter a password in the  
configuration file, the switch mistakenly attempts to execute the passwords as commands as it  
executes the file.  
Note  
The copy {ftp: | rcp: | tftp:} system:running-config privileged EXEC command loads the  
configuration files on the switch as if you were entering the commands at the command line. The switch  
does not erase the existing running configuration before adding the commands. If a command in the  
copied configuration file replaces a command in the existing configuration file, the existing command  
is erased. For example, if the copied configuration file contains a different IP address in a particular  
command than the existing configuration, the IP address in the copied configuration is used. However,  
some commands in the existing configuration might not be replaced or negated. In this case, the resulting  
configuration file is a mixture of the existing configuration file and the copied configuration file, with  
the copied configuration file having precedence.  
To restore a configuration file to an exact copy of a file stored on a server, copy the configuration file  
directly to the startup configuration (by using the copy {ftp: | rcp: | tftp:} nvram:startup-config  
privileged EXEC command), and reload the switch.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
Configuration File Types and Location  
Startup configuration files are used during system startup to configure the software. Running  
configuration files contain the current configuration of the software. The two configuration files can be  
different. For example, you might want to change the configuration for a short time period rather than  
permanently. In this case, you would change the running configuration but not save the configuration by  
using the copy running-config startup-config privileged EXEC command.  
The running configuration is saved in DRAM; the startup configuration is stored in the NVRAM section  
of flash memory.  
Creating a Configuration File By Using a Text Editor  
When creating a configuration file, you must list commands logically so that the system can respond  
appropriately. This is one method of creating a configuration file:  
Step 1  
Copy an existing configuration from a switch to a server.  
For more information, see the “Downloading the Configuration File By Using TFTP” section on  
page B-11, the “Downloading a Configuration File By Using FTP” section on page B-13, or the  
“Downloading a Configuration File By Using RCP” section on page B-17.  
Step 2  
Step 3  
Step 4  
Open the configuration file in a text editor, such as vi or emacs on UNIX or Notepad on a PC.  
Extract the portion of the configuration file with the desired commands, and save it in a new file.  
Copy the configuration file to the appropriate server location. For example, copy the file to the TFTP  
directory on the workstation (usually /tftpboot on a UNIX workstation).  
Step 5  
Make sure the permissions on the file are set to world-read.  
Copying Configuration Files By Using TFTP  
You can configure the switch by using configuration files you create, download from another switch, or  
download from a TFTP server. You can copy (upload) configuration files to a TFTP server for storage.  
This section includes this information:  
•
•
•
Preparing to Download or Upload a Configuration File By Using TFTP, page B-10  
Downloading the Configuration File By Using TFTP, page B-11  
Uploading the Configuration File By Using TFTP, page B-12  
Preparing to Download or Upload a Configuration File By Using TFTP  
Before you begin downloading or uploading a configuration file by using TFTP, do these tasks:  
•
Ensure that the workstation acting as the TFTP server is properly configured. On a Sun workstation,  
make sure that the /etc/inetd.conf file contains this line:  
tftp dgram udp wait root /usr/etc/in.tftpd in.tftpd -p -s /tftpboot  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
Make sure that the /etc/services file contains this line:  
tftp 69/udp  
Note  
You must restart the inetd daemon after modifying the /etc/inetd.conf and /etc/services files.  
To restart the daemon, either stop the inetd process and restart it, or enter a fastboot  
command (on the SunOS 4.x) or a reboot command (on Solaris 2.x or SunOS 5.x). For more  
information on the TFTP daemon, see the documentation for your workstation.  
•
Ensure that the switch has a route to the TFTP server. The switch and the TFTP server must be in  
the same subnetwork if you do not have a router to route traffic between subnets. Check connectivity  
to the TFTP server by using the ping command.  
•
•
•
Ensure that the configuration file to be downloaded is in the correct directory on the TFTP server  
(usually /tftpboot on a UNIX workstation).  
For download operations, ensure that the permissions on the file are set correctly. The permission  
on the file should be world-read.  
Before uploading the configuration file, you might need to create an empty file on the TFTP server.  
To create an empty file, enter the touch filename command, where filename is the name of the file  
you will use when uploading it to the server.  
•
During upload operations, if you are overwriting an existing file (including an empty file, if you had  
to create one) on the server, ensure that the permissions on the file are set correctly. Permissions on  
the file should be world-write.  
Downloading the Configuration File By Using TFTP  
To configure the switch by using a configuration file downloaded from a TFTP server, follow these  
steps:  
Step 1  
Step 2  
Copy the configuration file to the appropriate TFTP directory on the workstation.  
Verify that the TFTP server is properly configured by referring to the “Preparing to Download or Upload  
a Configuration File By Using TFTP” section on page B-10.  
Step 3  
Step 4  
Log into the switch through a Telnet session.  
Download the configuration file from the TFTP server to configure the switch.  
Specify the IP address or host name of the TFTP server and the name of the file to download.  
Use one of these privileged EXEC commands:  
•
•
copy tftp:[[[//location]/directory]/filename] system:running-config  
copy tftp:[[[//location]/directory]/filename] nvram:startup-config  
The configuration file downloads, and the commands are executed as the file is parsed line-by-line.  
This example shows how to configure the software from the file tokyo-confg at IP address 172.16.2.155:  
Switch# copy tftp://172.16.2.155/tokyo-confg system:running-config  
Configure using tokyo-confg from 172.16.2.155? [confirm] y  
Booting tokyo-confg from 172.16.2.155:!!! [OK - 874/16000 bytes]  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
Uploading the Configuration File By Using TFTP  
To upload a configuration file from a switch to a TFTP server for storage, follow these steps:  
Step 1  
Verify that the TFTP server is properly configured by referring to the “Preparing to Download or Upload  
a Configuration File By Using TFTP” section on page B-10.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
Upload the switch configuration to the TFTP server. Specify the IP address or host name of the TFTP  
server and the destination filename.  
Use one of these privileged EXEC commands:  
•
•
copy system:running-config tftp:[[[//location]/directory]/filename]  
copy nvram:startup-config tftp:[[[//location]/directory]/filename]  
The file is uploaded to the TFTP server.  
This example shows how to upload a configuration file from a switch to a TFTP server:  
Switch# copy system:running-config tftp://172.16.2.155/tokyo-confg  
Write file tokyo-confg on host 172.16.2.155? [confirm] y  
#
Writing tokyo-confg!!! [OK]  
Copying Configuration Files By Using FTP  
You can copy configuration files to or from an FTP server.  
The FTP protocol requires a client to send a remote username and password on each FTP request to a  
server. When you copy a configuration file from the switch to a server by using FTP, the software sends  
the first valid username in this list:  
•
•
The username specified in the copy command if a username is specified.  
The username set by the ip ftp username username global configuration command if the command  
is configured.  
•
Anonymous.  
The switch sends the first valid password in this list:  
•
•
The password specified in the copy command if a password is specified.  
The password set by the ip ftp password password global configuration command if the command  
is configured.  
•
The switch forms a password named [email protected]. The variable username is the  
username associated with the current session, switchname is the configured host name, and domain  
is the domain of the switch.  
The username and password must be associated with an account on the FTP server. If you are writing to  
the server, the FTP server must be properly configured to accept your FTP write request.  
Use the ip ftp username and ip ftp password commands to specify a username and password for all  
copies. Include the username in the copy command if you want to specify only a username for that copy  
operation.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
If the server has a directory structure, the configuration file is written to or copied from the directory  
associated with the username on the server. For example, if the configuration file is in the home directory  
of a user on the server, specify that user's name as the remote username.  
For more information, see the documentation for your FTP server.  
This section includes this information:  
•
•
•
Preparing to Download or Upload a Configuration File By Using FTP, page B-13  
Downloading a Configuration File By Using FTP, page B-13  
Uploading a Configuration File By Using FTP, page B-14  
Preparing to Download or Upload a Configuration File By Using FTP  
Before you begin downloading or uploading a configuration file by using FTP, do these tasks:  
•
Ensure that the switch has a route to the FTP server. The switch and the FTP server must be in the  
same subnetwork if you do not have a router to route traffic between subnets. Check connectivity to  
the FTP server by using the ping command.  
•
If you are accessing the switch through the console or a Telnet session and you do not have a valid  
username, make sure that the current FTP username is the one that you want to use for the FTP  
download. You can enter the show users privileged EXEC command to view the valid username. If  
you do not want to use this username, create a new FTP username by using the ip ftp username  
username global configuration command during all copy operations. The new username is stored in  
NVRAM. If you are accessing the switch through a Telnet session and you have a valid username,  
this username is used, and you do not need to set the FTP username. Include the username in the  
copy command if you want to specify a username for only that copy operation.  
•
When you upload a configuration file to the FTP server, it must be properly configured to accept the  
write request from the user on the switch.  
For more information, see the documentation for your FTP server.  
Downloading a Configuration File By Using FTP  
Beginning in privileged EXEC mode, follow these steps to download a configuration file by using FTP:  
Command  
Purpose  
Step 1  
Verify that the FTP server is properly configured by referring  
to the “Preparing to Download or Upload a Configuration  
File By Using FTP” section on page B-13.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
configure terminal  
Enter global configuration mode on the switch.  
This step is required only if you override the default remote  
username or password (see Steps 4, 5, and 6).  
Step 4  
Step 5  
ip ftp username username  
ip ftp password password  
(Optional) Change the default remote username.  
(Optional) Change the default password.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
Command  
Purpose  
Step 6  
Step 7  
end  
Return to privileged EXEC mode.  
copy  
Using FTP, copy the configuration file from a network server  
ftp:[[[//[username[:password]@]location]/directory] to the running configuration or to the startup configuration  
/filename] system:running-config  
file.  
or  
copy  
ftp:[[[//[username[:password]@]location]/directory]  
/filename] nvram:startup-config  
This example shows how to copy a configuration file named host1-confg from the netadmin1 directory  
on the remote server with an IP address of 172.16.101.101 and to load and run those commands on the  
switch:  
Switch# copy ftp://netadmin1:[email protected]/host1-confg system:running-config  
Configure using host1-confg from 172.16.101.101? [confirm]  
Connected to 172.16.101.101  
Loading 1112 byte file host1-confg:![OK]  
Switch#  
%SYS-5-CONFIG: Configured from host1-config by ftp from 172.16.101.101  
This example shows how to specify a remote username of netadmin1. The software copies the  
configuration file host2-confg from the netadmin1 directory on the remote server with an IP address  
of 172.16.101.101 to the switch startup configuration.  
Switch# configure terminal  
Switch(config)# ip ftp username netadmin1  
Switch(config)# ip ftp password mypass  
Switch(config)# end  
Switch# copy ftp: nvram:startup-config  
Address of remote host [255.255.255.255]? 172.16.101.101  
Name of configuration file[rtr2-confg]? host2-confg  
Configure using host2-confg from 172.16.101.101?[confirm]  
Connected to 172.16.101.101  
Loading 1112 byte file host2-confg:![OK]  
[OK]  
Switch#  
%SYS-5-CONFIG_NV:Non-volatile store configured from host2-config by ftp from  
172.16.101.101  
Uploading a Configuration File By Using FTP  
Beginning in privileged EXEC mode, follow these steps to upload a configuration file by using FTP:  
Command  
Purpose  
Step 1  
Verify that the FTP server is properly configured by referring  
to the “Preparing to Download or Upload a Configuration  
File By Using FTP” section on page B-13.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
Enter global configuration mode.  
configure terminal  
This step is required only if you override the default remote  
username or password (see Steps 4, 5, and 6).  
Step 4  
ip ftp username username  
(Optional) Change the default remote username.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
Command  
Purpose  
Step 5  
Step 6  
Step 7  
ip ftp password password  
end  
(Optional) Change the default password.  
Return to privileged EXEC mode.  
copy system:running-config  
Using FTP, store the switch running or startup configuration  
ftp:[[[//[username[:password]@]location]/directory] file to the specified location.  
/filename]  
or  
copy nvram:startup-config  
ftp:[[[//[username[:password]@]location]/directory]  
/filename]  
This example shows how to copy the running configuration file named switch2-confg to the netadmin1  
directory on the remote host with an IP address of 172.16.101.101:  
Switch# copy system:running-config ftp://netadmin1:[email protected]/switch2-confg  
Write file switch2-confg on host 172.16.101.101?[confirm]  
Building configuration...[OK]  
Connected to 172.16.101.101  
Switch#  
This example shows how to store a startup configuration file on a server by using FTP to copy the file:  
Switch# configure terminal  
Switch(config)# ip ftp username netadmin2  
Switch(config)# ip ftp password mypass  
Switch(config)# end  
Switch# copy nvram:startup-config ftp:  
Remote host[]? 172.16.101.101  
Name of configuration file to write [switch2-confg]?  
Write file switch2-confg on host 172.16.101.101?[confirm]  
![OK]  
Copying Configuration Files By Using RCP  
The RCP provides another method of downloading, uploading, and copying configuration files between  
remote hosts and the switch. Unlike TFTP, which uses User Datagram Protocol (UDP), a connectionless  
protocol, RCP uses TCP, which is connection-oriented.  
To use RCP to copy files, the server from or to which you will be copying files must support RCP. The  
RCP copy commands rely on the rsh server (or daemon) on the remote system. To copy files by using  
RCP, you do not need to create a server for file distribution as you do with TFTP. You only need to have  
access to a server that supports the remote shell (rsh). (Most UNIX systems support rsh.) Because you  
are copying a file from one place to another, you must have read permission on the source file and write  
permission on the destination file. If the destination file does not exist, RCP creates it for you.  
The RCP requires a client to send a remote username with each RCP request to a server. When you copy  
a configuration file from the switch to a server, the software sends the first valid username in this list:  
•
•
The username specified in the copy command if a username is specified.  
The username set by the ip rcmd remote-username username global configuration command if the  
command is configured.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
•
•
The remote username associated with the current TTY (terminal) process. For example, if the user  
is connected to the router through Telnet and was authenticated through the username command,  
the switch software sends the Telnet username as the remote username.  
The switch host name.  
For a successful RCP copy request, you must define an account on the network server for the remote  
username. If the server has a directory structure, the configuration file is written to or copied from the  
directory associated with the remote username on the server. For example, if the configuration file is in  
the home directory of a user on the server, specify that user's name as the remote username.  
This section includes this information:  
•
•
•
Preparing to Download or Upload a Configuration File By Using RCP, page B-16  
Downloading a Configuration File By Using RCP, page B-17  
Uploading a Configuration File By Using RCP, page B-18  
Preparing to Download or Upload a Configuration File By Using RCP  
Before you begin downloading or uploading a configuration file by using RCP, do these tasks:  
•
•
Ensure that the workstation acting as the RCP server supports the remote shell (rsh).  
Ensure that the switch has a route to the RCP server. The switch and the server must be in the same  
subnetwork if you do not have a router to route traffic between subnets. Check connectivity to the  
RCP server by using the ping command.  
•
If you are accessing the switch through the console or a Telnet session and you do not have a valid  
username, make sure that the current RCP username is the one that you want to use for the RCP  
download. You can enter the show users privileged EXEC command to view the valid username. If  
you do not want to use this username, create a new RCP username by using the ip rcmd  
remote-username username global configuration command to be used during all copy operations.  
The new username is stored in NVRAM. If you are accessing the switch through a Telnet session  
and you have a valid username, this username is used, and you do not need to set the RCP username.  
Include the username in the copy command if you want to specify a username for only that copy  
operation.  
•
When you upload a file to the RCP server, it must be properly configured to accept the RCP write  
request from the user on the switch. For UNIX systems, you must add an entry to the .rhosts file for  
the remote user on the RCP server. For example, suppose that the switch contains these  
configuration lines:  
hostname Switch1  
ip rcmd remote-username User0  
If the switch IP address translates to Switch1.company.com, the .rhosts file for User0 on the RCP  
server should contain this line:  
Switch1.company.com Switch1  
For more information, see the documentation for your RCP server.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
Downloading a Configuration File By Using RCP  
Beginning in privileged EXEC mode, follow these steps to download a configuration file by using RCP:  
Command  
Purpose  
Step 1  
Verify that the RCP server is properly configured by  
referring to the “Preparing to Download or Upload a  
Configuration File By Using RCP” section on page B-16.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
configure terminal  
Enter global configuration mode.  
This step is required only if you override the default remote  
username (see Steps 4 and 5).  
Step 4  
Step 5  
Step 6  
ip rcmd remote-username username  
(Optional) Specify the remote username.  
Return to privileged EXEC mode.  
end  
copy  
Using RCP, copy the configuration file from a network  
rcp:[[[//[username@]location]/directory]/filename] server to the running configuration or to the startup  
system:running-config  
configuration file.  
or  
copy  
rcp:[[[//[username@]location]/directory]/filename]  
nvram:startup-config  
This example shows how to copy a configuration file named host1-confg from the netadmin1 directory  
on the remote server with an IP address of 172.16.101.101 and load and run those commands on the  
switch:  
Switch# copy rcp://[email protected]/host1-confg system:running-config  
Configure using host1-confg from 172.16.101.101? [confirm]  
Connected to 172.16.101.101  
Loading 1112 byte file host1-confg:![OK]  
Switch#  
%SYS-5-CONFIG: Configured from host1-config by rcp from 172.16.101.101  
This example shows how to specify a remote username of netadmin1. Then it copies the configuration  
file host2-confg from the netadmin1 directory on the remote server with an IP address of 172.16.101.101  
to the startup configuration:  
Switch# configure terminal  
Switch(config)# ip rcmd remote-username netadmin1  
Switch(config)# end  
Switch# copy rcp: nvram:startup-config  
Address of remote host [255.255.255.255]? 172.16.101.101  
Name of configuration file[rtr2-confg]? host2-confg  
Configure using host2-confg from 172.16.101.101?[confirm]  
Connected to 172.16.101.101  
Loading 1112 byte file host2-confg:![OK]  
[OK]  
Switch#  
%SYS-5-CONFIG_NV:Non-volatile store configured from host2-config by rcp from  
172.16.101.101  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Configuration Files  
Uploading a Configuration File By Using RCP  
Beginning in privileged EXEC mode, follow these steps to upload a configuration file by using RCP:  
Command  
Purpose  
Step 1  
Verify that the RCP server is properly configured by  
referring to the “Preparing to Download or Upload a  
Configuration File By Using RCP” section on page B-16.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
Enter global configuration mode.  
configure terminal  
This step is required only if you override the default remote  
username (see Steps 4 and 5).  
Step 4  
Step 5  
Step 6  
ip rcmd remote-username username  
end  
(Optional) Specify the remote username.  
Return to privileged EXEC mode.  
copy system:running-config  
Using RCP, copy the configuration file from a switch running  
rcp:[[[//[username@]location]/directory]/filename] or startup configuration file to a network server.  
or  
copy nvram:startup-config  
rcp:[[[//[username@]location]/directory]/filename]  
This example shows how to copy the running configuration file named switch2-confg to the netadmin1  
directory on the remote host with an IP address of 172.16.101.101:  
Switch# copy system:running-config rcp://[email protected]/switch2-confg  
Write file switch-confg on host 172.16.101.101?[confirm]  
Building configuration...[OK]  
Connected to 172.16.101.101  
Switch#  
This example shows how to store a startup configuration file on a server:  
Switch# configure terminal  
Switch(config)# ip rcmd remote-username netadmin2  
Switch(config)# end  
Switch# copy nvram:startup-config rcp:  
Remote host[]? 172.16.101.101  
Name of configuration file to write [switch2-confg]?  
Write file switch2-confg on host 172.16.101.101?[confirm]  
![OK]  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
Clearing Configuration Information  
You can clear the configuration information from the startup configuration.  
Clearing the Startup Configuration File  
To clear the contents of your startup configuration, use the erase nvram: or the erase startup-config  
privileged EXEC command.  
Caution  
You cannot restore the startup configuration file after it has been deleted.  
Deleting a Stored Configuration File  
To delete a saved configuration from flash memory, use the delete flash:filename privileged EXEC  
command. Depending on the setting of the file prompt global configuration command, you might be  
prompted for confirmation before you delete a file. By default, the switch prompts for confirmation on  
destructive file operations. For more information about the file prompt command, see the Cisco IOS  
Command Reference for Release 12.1.  
Caution  
You cannot restore a file after it has been deleted.  
Working with Software Images  
This section describes how to archive (download and upload) software image files, which contain the  
system software, Cisco IOS code, and the embedded device manager software.  
You can download a switch image file from a TFTP, FTP, or RCP server to upgrade the switch software.  
You can replace the current image with the new one or keep the current image in flash memory after a  
download.  
You upload a switch image file to a TFTP, FTP, or RCP server for backup purposes. You can use this  
uploaded image for future downloads to the same switch or another of the same type.  
The protocol that you use depends on which type of server that you are using. The FTP and RCP  
transport mechanisms provide faster performance and more reliable delivery of data than TFTP. These  
improvements are possible because FTP and RCP are built on and use the TCP/IP stack, which is  
connection-oriented.  
This section includes this information:  
•
•
•
•
•
Image Location on the Switch, page B-20  
tar File Format of Images on a Server or IBM.com, page B-20  
Copying Image Files By Using TFTP, page B-21  
Copying Image Files By Using FTP, page B-24  
Copying Image Files By Using RCP, page B-28  
Note  
For a list of software images and the supported upgrade paths, see the release notes.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
Image Location on the Switch  
The software image is stored as a .bin file in a directory that shows the version number. A subdirectory  
contains the HTML files needed for web management. The image is stored on the system board flash  
memory (flash:).  
You can use the show version privileged EXEC command to see the software version that is currently  
running on your switch. In the display, check the line that begins with System image file is.... It  
shows the directory name in flash memory where the image is stored.  
You can also use the dir filesystem: privileged EXEC command to see the directory names of other  
software images you might have stored in flash memory.  
tar File Format of Images on a Server or IBM.com  
Software images located on a server or downloaded from ibm.com are provided in a tar file format,  
which contains these files:  
•
info file  
The info file is always at the beginning of the tar file and has information about the files within it.  
•
•
•
Cisco IOS image  
Web management files needed by the HTTP server on the switch  
info.ver file  
The info.ver file is always at the end of the tar file and has the same information as the info file.  
Because it is the last file in the tar file, its existence means that all files in the image have been  
downloaded.  
This example shows the information in the info and info.ver files:  
version_suffix:i6q4l2-121-0.0.42.EA1  
version_directory:cigesm-i6q4l2-mz.121-0.0.42.EA1  
image_name:cigesm-i6q4l2-mz.121-0.0.42.EA1.bin  
ios_image_file_size:3038720  
total_image_file_size:5404672  
image_feature:LAYER_2|MIN_DRAM_MEG=32  
image_family:CIGESM  
image_min_dram:32  
info_end:  
Table B-3  
info and info.ver File Description  
Field  
Description  
version_suffix  
version_directory  
image_name  
Specifies the software image version string suffix  
Specifies the directory where the software image and the HTML subdirectory are installed  
Specifies the name of the software image within the tar file  
ios_image_file_size  
total_image_file_size  
image_feature  
Specifies the software image size in the tar file, which is an approximate measure of how much  
flash space is required to hold just the software image  
Specifies the size of all the images (the software image and the HTML files) in the tar file,  
which is an approximate measure of how much flash space is required to hold them  
Describes the core functionality of the image  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
Table B-3  
info and info.ver File Description (continued)  
Field  
Description  
image_family  
image_min_dram  
Describes the family of products on which the software can be installed  
Specifies the minimum amount of DRAM needed to run this image  
Copying Image Files By Using TFTP  
You can download a switch image from a TFTP server or upload the image from the switch to a TFTP  
server.  
You download a switch image file from a server to upgrade the switch software. You can overwrite the  
current image with the new one or keep the current image after a download.  
You upload a switch image file to a server for backup purposes; this uploaded image can be used for  
future downloads to the same or another switch of the same type.  
This section includes this information:  
•
•
•
Preparing to Download or Upload an Image File By Using TFTP, page B-21  
Downloading an Image File By Using TFTP, page B-22  
Uploading an Image File By Using TFTP, page B-23  
Preparing to Download or Upload an Image File By Using TFTP  
Before you begin downloading or uploading an image file by using TFTP, do these tasks:  
•
Ensure that the workstation acting as the TFTP server is properly configured. On a Sun workstation,  
make sure that the /etc/inetd.conf file contains this line:  
tftp dgram udp wait root /usr/etc/in.tftpd in.tftpd -p -s /tftpboot  
Make sure that the /etc/services file contains this line:  
tftp 69/udp  
Note  
You must restart the inetd daemon after modifying the /etc/inetd.conf and /etc/services files.  
To restart the daemon, either stop the inetd process and restart it, or enter a fastboot  
command (on the SunOS 4.x) or a reboot command (on Solaris 2.x or SunOS 5.x). For more  
information on the TFTP daemon, see the documentation for your workstation.  
•
Ensure that the switch has a route to the TFTP server. The switch and the TFTP server must be in  
the same subnetwork if you do not have a router to route traffic between subnets. Check connectivity  
to the TFTP server by using the ping command.  
•
•
Ensure that the image to be downloaded is in the correct directory on the TFTP server (usually  
/tftpboot on a UNIX workstation).  
For download operations, ensure that the permissions on the file are set correctly. The permission  
on the file should be world-read.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
•
•
Before uploading the image file, you might need to create an empty file on the TFTP server. To  
create an empty file, enter the touch filename command, where filename is the name of the file you  
will use when uploading the image to the server.  
During upload operations, if you are overwriting an existing file (including an empty file, if you had  
to create one) on the server, ensure that the permissions on the file are set correctly. Permissions on  
the file should be world-write.  
Downloading an Image File By Using TFTP  
You can download a new image file and replace the current image or keep the current image.  
Beginning in privileged EXEC mode, follow Steps 1 through 3 to download a new image from a TFTP  
server and overwrite the existing image. To keep the current image, omit Step 3.  
Command  
Purpose  
Step 1  
Copy the image to the appropriate TFTP directory on the  
workstation. Make sure that the TFTP server is properly  
configured; see the “Preparing to Download or Upload an Image  
File By Using TFTP” section on page B-21.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
archive download-sw /overwrite /reload  
tftp:[[//location]/directory]/image-name.tar  
Download the image file from the TFTP server to the switch, and  
overwrite the current image.  
•
The /overwrite option overwrites the software image in flash  
with the downloaded image only if the version of the image  
being downloaded is the same as the existing copy in flash  
memory.  
•
The /reload option reloads the system after downloading the  
image unless the configuration has been changed and not been  
saved.  
•
•
For //location, specify the IP address of the TFTP server.  
For /directory/image-name.tar, specify the directory  
(optional) and the image to download. Directory and image  
names are case sensitive.  
Step 4  
archive download-sw /leave-old-sw /reload  
tftp:[[//location]/directory]/image-name.tar  
Download the image file from the TFTP server to the switch, and  
keep the current image.  
•
The /leave-old-sw option keeps the old software version after  
a download.  
•
The /reload option reloads the system after downloading the  
image unless the configuration has been changed and not been  
saved.  
•
•
For //location, specify the IP address of the TFTP server.  
For /directory/image-name.tar, specify the directory  
(optional) and the image to download. Directory and image  
names are case sensitive.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
The download algorithm verifies that the image is appropriate for the switch model and that enough  
DRAM is present, or it stops the process and reports an error. If you specify the /overwrite option, the  
download algorithm removes the existing image on the flash device whether or not it is the same as the  
new one, downloads the new image, and then reloads the software.  
Note  
If the flash device has sufficient space to hold two images and you want to overwrite one of these images  
with the same version, you must specify the /overwrite option.  
If you specify the /leave-old-sw, the existing files are not removed. If there is not enough space to install  
the new image and keep the current running image, the download process stops, and an error message  
appears.  
The algorithm installs the downloaded image on the system board flash device (flash:). The image is  
placed into a new directory named with the software version string, and the BOOT environment variable  
is updated to point to the newly installed image.  
If you kept the old image during the download process (you specified the /leave-old-sw keyword), you  
can remove it by entering the delete /force /recursive filesystem:/file-url privileged EXEC command.  
For filesystem, use flash: for the system board flash device. For file-url, enter the directory name of the  
old image. All the files in the directory and the directory are removed.  
Caution  
For the download and upload algorithms to operate properly, do not rename image names.  
Uploading an Image File By Using TFTP  
You can upload an image from the switch to a TFTP server. You can later download this image to the  
switch or to another switch of the same type.  
Use the upload feature only if the HTML pages associated with the device manager have been installed  
with the existing image.  
Beginning in privileged EXEC mode, follow these steps to upload an image to a TFTP server:  
Command  
Purpose  
Step 1  
Make sure that the TFTP server is properly configured; see the  
“Preparing to Download or Upload an Image File By Using TFTP”  
section on page B-21.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
archive upload-sw  
Upload the currently running switch image to the TFTP server.  
tftp:[[//location]/directory]/image-name.tar  
•
•
For //location, specify the IP address of the TFTP server.  
For /directory/image-name.tar, specify the directory (optional)  
and the name of the software image to be uploaded. Directory  
and image names are case sensitive. The image-name.tar is the  
name of the software image to be stored on the server.  
The archive upload-sw privileged EXEC command builds an image file on the server by uploading  
these files in order: info, the Cisco IOS image, the HTML files, and info.ver. After these files are  
uploaded, the upload algorithm creates the tar file format.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
Caution  
For the download and upload algorithms to operate properly, do not rename image names.  
Copying Image Files By Using FTP  
You can download a switch image from an FTP server or upload the image from the switch to an FTP  
server.  
You download a switch image file from a server to upgrade the switch software. You can overwrite the  
current image with the new one or keep the current image after a download.  
You upload a switch image file to a server for backup purposes. You can use this uploaded image for  
future downloads to the switch or another switch of the same type.  
This section includes this information:  
•
•
•
Preparing to Download or Upload an Image File By Using FTP, page B-24  
Downloading an Image File By Using FTP, page B-25  
Uploading an Image File By Using FTP, page B-27  
Preparing to Download or Upload an Image File By Using FTP  
You can copy images files to or from an FTP server.  
The FTP protocol requires a client to send a remote username and password on each FTP request to a  
server. When you copy an image file from the switch to a server by using FTP, the software sends the  
first valid username in this list:  
•
•
•
The username specified in the archive download-sw or archive upload-sw privileged EXEC  
command if a username is specified.  
The username set by the ip ftp username username global configuration command if the command  
is configured.  
Anonymous.  
The switch sends the first valid password in this list:  
•
•
•
The password specified in the archive download-sw or archive upload-sw privileged EXEC  
command if a password is specified.  
The password set by the ip ftp password password global configuration command if the command  
is configured.  
The switch forms a password named [email protected]. The variable username is the  
username associated with the current session, switchname is the configured host name, and domain  
is the domain of the switch.  
The username and password must be associated with an account on the FTP server. If you are writing to  
the server, the FTP server must be properly configured to accept the FTP write request from you.  
Use the ip ftp username and ip ftp password commands to specify a username and password for all  
copies. Include the username in the archive download-sw or archive upload-sw privileged EXEC  
command if you want to specify a username only for that operation.  
If the server has a directory structure, the image file is written to or copied from the directory associated  
with the username on the server. For example, if the image file resides in the home directory of a user  
on the server, specify that user's name as the remote username.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
Before you begin downloading or uploading an image file by using FTP, do these tasks:  
•
Ensure that the switch has a route to the FTP server. The switch and the FTP server must be in the  
same subnetwork if you do not have a router to route traffic between subnets. Check connectivity to  
the FTP server by using the ping command.  
•
If you are accessing the switch through the console or a Telnet session and you do not have a valid  
username, make sure that the current FTP username is the one that you want to use for the FTP  
download. You can enter the show users privileged EXEC command to view the valid username. If  
you do not want to use this username, create a new FTP username by using the ip ftp username  
username global configuration command. This new name will be used during all archive operations.  
The new username is stored in NVRAM. If you are accessing the switch through a Telnet session  
and you have a valid username, this username is used, and you do not need to set the FTP username.  
Include the username in the archive download-sw or archive upload-sw privileged EXEC  
command if you want to specify a username for that operation only.  
•
When you upload an image file to the FTP server, it must be properly configured to accept the write  
request from the user on the switch.  
For more information, see the documentation for your FTP server.  
Downloading an Image File By Using FTP  
You can download a new image file and overwrite the current image or keep the current image.  
Beginning in privileged EXEC mode, follow Steps 1 through 7 to download a new image from an FTP  
server and overwrite the existing image. To keep the current image, omit Step 7.  
Command  
Purpose  
Step 1  
Verify that the FTP server is properly configured by referring  
to the “Preparing to Download or Upload an Image File By  
Using FTP” section on page B-24.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
configure terminal  
Enter global configuration mode.  
This step is required only if you override the default remote  
username or password (see Steps 4, 5, and 6).  
Step 4  
Step 5  
Step 6  
ip ftp username username  
ip ftp password password  
end  
(Optional) Change the default remote username.  
(Optional) Change the default password.  
Return to privileged EXEC mode.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
Command  
Purpose  
Step 7  
archive download-sw /overwrite /reload  
Download the image file from the FTP server to the switch,  
ftp:[[//username[:password]@location]/directory] and overwrite the current image.  
/image-name.tar  
•
•
The /overwrite option overwrites the software image in  
flash with the downloaded image.  
The /reload option reloads the system after downloading  
the image unless the configuration has been changed and  
not been saved.  
•
For //username[:password], specify the username and  
password; these must be associated with an account on the  
FTP server. For more information, see the “Preparing to  
Download or Upload an Image File By Using FTP”  
section on page B-24.  
•
•
For @location, specify the IP address of the FTP server.  
For directory/image-name.tar, specify the directory  
(optional) and the image to download. Directory and  
image names are case sensitive.  
Step 8  
archive download-sw /leave-old-sw /reload  
Download the image file from the FTP server to the switch,  
ftp:[[//username[:password]@location]/directory] and keep the current image.  
/image-name.tar  
•
•
The /leave-old-sw option keeps the old software version  
after a download.  
The /reload option reloads the system after downloading  
the image unless the configuration has been changed and  
not been saved.  
•
For //username[:password], specify the username and  
password. These must be associated with an account on  
the FTP server. For more information, see the “Preparing  
to Download or Upload an Image File By Using FTP”  
section on page B-24.  
•
•
For @location, specify the IP address of the FTP server.  
For directory/image-name.tar, specify the directory  
(optional) and the image to download. Directory and  
image names are case sensitive.  
The download algorithm verifies that the image is appropriate for the switch model and that enough  
DRAM is present, or it stops the process and reports an error. If you specify the /overwrite option, the  
download algorithm removes the existing image on the flash device, whether or not it is the same as the  
new one, downloads the new image, and then reloads the software.  
Note  
If the flash device has sufficient space to hold two images and you want to overwrite one of these images  
with the same version, you must specify the /overwrite option.  
If you specify the /leave-old-sw, the existing files are not removed. If there is not enough space to install  
the new image and keep the running image, the download process stops, and an error message appears.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
The algorithm installs the downloaded image onto the system board flash device (flash:). The image is  
placed into a new directory named with the software version string, and the BOOT environment variable  
is updated to point to the newly installed image.  
If you kept the old image during the download process (you specified the /leave-old-sw keyword), you  
can remove it by entering the delete /force /recursive filesystem:/file-url privileged EXEC command.  
For filesystem, use flash: for the system board flash device. For file-url, enter the directory name of the  
old software image. All the files in the directory and the directory are removed.  
Caution  
For the download and upload algorithms to operate properly, do not rename image names.  
Uploading an Image File By Using FTP  
You can upload an image from the switch to an FTP server. You can later download this image to the  
same switch or to another switch of the same type.  
Use the upload feature only if the HTML pages associated with the device manager have been installed  
with the existing image.  
Beginning in privileged EXEC mode, follow these steps to upload an image to an FTP server:  
Command  
Purpose  
Step 1  
Verify that the FTP server is properly configured by referring  
to the “Preparing to Download or Upload a Configuration  
File By Using FTP” section on page B-13.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
configure terminal  
Enter global configuration mode.  
This step is required only if you override the default remote  
username or password (see Steps 4, 5, and 6).  
Step 4  
Step 5  
Step 6  
Step 7  
ip ftp username username  
ip ftp password password  
end  
(Optional) Change the default remote username.  
(Optional) Change the default password.  
Return to privileged EXEC mode.  
archive upload-sw  
Upload the currently running switch image to the FTP server.  
ftp:[[//[username[:password]@]location]/directory]/  
image-name.tar  
•
For //username:password, specify the username and  
password. These must be associated with an account on  
the FTP server. For more information, see the “Preparing  
to Download or Upload an Image File By Using FTP”  
section on page B-24.  
•
•
For @location, specify the IP address of the FTP server.  
For /directory/image-name.tar, specify the directory  
(optional) and the name of the software image to be  
uploaded. Directory and image names are case sensitive.  
The image-name.tar is the name of the software image  
to be stored on the server.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
The archive upload-sw command builds an image file on the server by uploading these files in order:  
info, the Cisco IOS image, the HTML files, and info.ver. After these files are uploaded, the upload  
algorithm creates the tar file format.  
Caution  
For the download and upload algorithms to operate properly, do not rename image names.  
Copying Image Files By Using RCP  
You can download a switch image from an RCP server or upload the image from the switch to an RCP  
server.  
You download a switch image file from a server to upgrade the switch software. You can overwrite the  
current image with the new one or keep the current image after a download.  
You upload a switch image file to a server for backup purposes. You can use this uploaded image for  
future downloads to the same switch or another of the same type.  
This section includes this information:  
•
•
•
Preparing to Download or Upload an Image File By Using RCP, page B-28  
Downloading an Image File By Using RCP, page B-29  
Uploading an Image File By Using RCP, page B-31  
Preparing to Download or Upload an Image File By Using RCP  
RCP provides another method of downloading and uploading image files between remote hosts and the  
switch. Unlike TFTP, which uses User Datagram Protocol (UDP), a connectionless protocol, RCP uses  
TCP, which is connection-oriented.  
To use RCP to copy files, the server from or to which you will be copying files must support RCP. The  
RCP copy commands rely on the rsh server (or daemon) on the remote system. To copy files by using  
RCP, you do not need to create a server for file distribution as you do with TFTP. You only need to have  
access to a server that supports the remote shell (rsh). (Most UNIX systems support rsh.) Because you  
are copying a file from one place to another, you must have read permission on the source file and write  
permission on the destination file. If the destination file does not exist, RCP creates it for you.  
RCP requires a client to send a remote username on each RCP request to a server. When you copy an  
image from the switch to a server by using RCP, the software sends the first valid username in this list:  
•
•
•
The username specified in the archive download-sw or archive upload-sw privileged EXEC  
command if a username is specified.  
The username set by the ip rcmd remote-username username global configuration command if the  
command is entered.  
The remote username associated with the current TTY (terminal) process. For example, if the user  
is connected to the router through Telnet and was authenticated through the username command,  
the switch software sends the Telnet username as the remote username.  
•
The switch host name.  
For the RCP copy request to execute successfully, an account must be defined on the network server for  
the remote username. If the server has a directory structure, the image file is written to or copied from  
the directory associated with the remote username on the server. For example, if the image file resides  
in the home directory of a user on the server, specify that user’s name as the remote username.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
Before you begin downloading or uploading an image file by using RCP, do these tasks:  
•
•
Ensure that the workstation acting as the RCP server supports the remote shell (rsh).  
Ensure that the switch has a route to the RCP server. The switch and the server must be in the same  
subnetwork if you do not have a router to route traffic between subnets. Check connectivity to the  
RCP server by using the ping command.  
•
If you are accessing the switch through the console or a Telnet session and you do not have a valid  
username, make sure that the current RCP username is the one that you want to use for the RCP  
download. You can enter the show users privileged EXEC command to view the valid username. If  
you do not want to use this username, create a new RCP username by using the ip rcmd  
remote-username username global configuration command to be used during all archive  
operations. The new username is stored in NVRAM. If you are accessing the switch through a Telnet  
session and you have a valid username, this username is used, and there is no need to set the RCP  
username. Include the username in the archive download-sw or archive upload-sw privileged  
EXEC command if you want to specify a username only for that operation.  
•
When you upload an image to the RCP to the server, it must be properly configured to accept the  
RCP write request from the user on the switch. For UNIX systems, you must add an entry to the  
.rhosts file for the remote user on the RCP server. For example, suppose the switch contains these  
configuration lines:  
hostname Switch1  
ip rcmd remote-username User0  
If the switch IP address translates to Switch1.company.com, the .rhosts file for User0 on the RCP  
server should contain this line:  
Switch1.company.com Switch1  
For more information, see the documentation for your RCP server.  
Downloading an Image File By Using RCP  
You can download a new image file and replace or keep the current image.  
Beginning in privileged EXEC mode, follow Steps 1 through 6 to download a new image from an RCP  
server and overwrite the existing image. To keep the current image, omit Step 6.  
Command  
Purpose  
Step 1  
Verify that the RCP server is properly configured by  
referring to the “Preparing to Download or Upload an Image  
File By Using RCP” section on page B-28.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
configure terminal  
Enter global configuration mode.  
This step is required only if you override the default remote  
username (see Steps 4 and 5).  
Step 4  
Step 5  
ip rcmd remote-username username  
(Optional) Specify the remote username.  
Return to privileged EXEC mode.  
end  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
Command  
Purpose  
Step 6  
archive download-sw /overwrite /reload  
Download the image file from the RCP server to the switch,  
rcp:[[[//[username@]location]/directory]/image-na and overwrite the current image.  
me.tar]  
•
•
The /overwrite option overwrites the software image in  
flash with the downloaded image.  
The /reload option reloads the system after  
downloading the image unless the configuration has  
been changed and not been saved.  
•
For //username, specify the username. For the RCP copy  
request to execute successfully, an account must be  
defined on the network server for the remote username.  
For more information, see the “Preparing to Download  
or Upload an Image File By Using RCP” section on  
page B-28.  
•
•
For @location, specify the IP address of the RCP server.  
For /directory/image-name.tar, specify the directory  
(optional) and the image to download. Directory and  
image names are case sensitive.  
Step 7  
archive download-sw /leave-old-sw /reload  
Download the image file from the RCP server to the switch,  
rcp:[[[//[username@]location]/directory]/image-na and keep the current image.  
me.tar]  
•
•
The /leave-old-sw option keeps the old software version  
after a download.  
The /reload option reloads the system after  
downloading the image unless the configuration has  
been changed and not been saved.  
•
For //username, specify the username. For the RCP copy  
request to execute, an account must be defined on the  
network server for the remote username. For more  
information, see the “Preparing to Download or Upload  
an Image File By Using RCP” section on page B-28.  
•
•
For @location, specify the IP address of the RCP server.  
For /directory]/image-name.tar, specify the directory  
(optional) and the image to download. Directory and  
image names are case sensitive.  
The download algorithm verifies that the image is appropriate for the switch model and that enough  
DRAM is present, or it stops the process and reports an error. If you specify the /overwrite option, the  
download algorithm removes the existing image on the flash device whether or not it is the same as the  
new one, downloads the new image, and then reloads the software.  
Note  
If the flash device has sufficient space to hold two images and you want to overwrite one of these images  
with the same version, you must specify the /overwrite option.  
If you specify the /leave-old-sw, the existing files are not removed. If there is not enough room to install  
the new image an keep the running image, the download process stops, and an error message appears.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
The algorithm installs the downloaded image onto the system board flash device (flash:). The image is  
placed in a new directory named with the software version string, and the BOOT environment variable  
is updated to point to the newly installed image.  
If you kept the old software during the download process (you specified the /leave-old-sw keyword),  
you can remove it by entering the delete /force /recursive filesystem:/file-url privileged EXEC  
command. For filesystem, use flash: for the system board flash device. For file-url, enter the directory  
name of the old software image. All the files in the directory and the directory are removed.  
Caution  
For the download and upload algorithms to operate properly, do not rename image names.  
Uploading an Image File By Using RCP  
You can upload an image from the switch to an RCP server. You can later download this image to the  
same switch or to another switch of the same type.  
The upload feature should be used only if the HTML pages associated with the device manager have  
been installed with the existing image.  
Beginning in privileged EXEC mode, follow these steps to upload an image to an RCP server:  
Command  
Purpose  
Step 1  
Verify that the RCP server is properly configured by  
referring to the “Preparing to Download or Upload an Image  
File By Using RCP” section on page B-28.  
Step 2  
Step 3  
Log into the switch through a Telnet session.  
configure terminal  
Enter global configuration mode.  
This step is required only if you override the default remote  
username (see Steps 4 and 5).  
Step 4  
Step 5  
Step 6  
ip rcmd remote-username username  
(Optional) Specify the remote username.  
Return to privileged EXEC mode.  
end  
archive upload-sw  
Upload the currently running switch image to the RCP  
rcp:[[[//[username@]location]/directory]/image-na server.  
me.tar]  
•
For //username, specify the username; for the RCP copy  
request to execute, an account must be defined on the  
network server for the remote username. For more  
information, see the “Preparing to Download or Upload  
an Image File By Using RCP” section on page B-28.  
•
•
For @location, specify the IP address of the RCP server.  
For /directory]/image-name.tar, specify the directory  
(optional) and the name of the software image to be  
uploaded. Directory and image names are case sensitive.  
•
The image-name.tar is the name of software image to be  
stored on the server.  
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Appendix B Working with the Cisco IOS File System, Configuration Files, and Software Images  
Working with Software Images  
The archive upload-sw privileged EXEC command builds an image file on the server by uploading  
these files in order: info, the Cisco IOS image, the HTML files, and info.ver. After these files are  
uploaded, the upload algorithm creates the tar file format.  
Caution  
For the download and upload algorithms to operate properly, do not rename image names.  
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A P P E N D I X  
C
Getting Help and Technical Assistance  
If you need help, service, or technical assistance or just want more information about IBM products, you  
will find a wide variety of sources available from IBM to assist you. This appendix contains information  
about where to go for additional information about IBM and IBM products, what to do if you experience  
a problem with your BladeCenter system, and whom to call for service, if it is necessary.  
Before You Call  
Before you call, make sure that you have taken these steps to try to solve the problem yourself:  
•
•
•
Check all cables to make sure that they are connected.  
Check the power switches to make sure that the system is turned on.  
Use the troubleshooting information in your system documentation, and use the diagnostic tools that  
come with your system. Information about diagnostic tools is in the Hardware Maintenance Manual  
and Troubleshooting Guide on the IBM BladeCenter Documentation CD or at the IBM Support Web  
site.  
•
Go to the IBM Support Web site at http://www.ibm.com/pc/support/ to check for technical  
information, hints, tips, and new device drivers.  
You can solve many problems without outside assistance by following the troubleshooting procedures  
that IBM provides in the online help or in the publications that are provided with your system and  
software. The information that comes with your system also describes the diagnostic tests that you can  
perform. Most xSeries and IntelliStation® systems, operating systems, and programs come with  
information that contains troubleshooting procedures and explanations of error messages and error  
codes. If you suspect a software problem, see the information for the operating system or program.  
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Appendix C Getting Help and Technical Assistance  
Using the Documentation  
Using the Documentation  
Information about your IBM BladeCenter, xSeries, or IntelliStation system and preinstalled software, if  
any, is available in the documentation that comes with your system. That documentation includes printed  
books, online books, readme files, and help files. See the troubleshooting information in your system  
documentation for instructions for using the diagnostic programs. The troubleshooting information or  
the diagnostic programs might tell you that you need additional or updated device drivers or other  
software. IBM maintains pages on the World Wide Web where you can get the latest technical  
information and download device drivers and updates. To access these pages, go to  
http://www.ibm.com/pc/support/ and follow the instructions. Also, you can order publications through  
the IBM Publications Ordering System at  
http://www.elink.ibmlink.ibm.com/public/applications/publications/cgibin/pbi.cgi.  
Getting Help and Information from the World Wide Web  
On the World Wide Web, the IBM Web site has up-to-date information about IBM BladeCenter, xSeries,  
and IntelliStation products, services, and support. The address for IBM BladeCenter and xSeries  
information is http://www.ibm.com/xseries/. The address for IBM IntelliStation information is  
http://www.ibm.com/pc/intellistation/.  
You can find service information for your IBM products, including supported options, at  
http://www.ibm.com/pc/support/.  
Software Service and Support  
Through IBM Support Line, you can get telephone assistance, for a fee, with usage, configuration, and  
software problems with BladeCenter and xSeries servers, IntelliStation workstations, and appliances.  
For information about which products are supported by Support Line in your country or region, go to  
http://www.ibm.com/services/sl/products/.  
For more information about Support Line and other IBM services, go to http://www.ibm.com/services/,  
or go to http://www.ibm.com/planetwide/ for support telephone numbers. In the U.S. and Canada, call  
1-800-IBM-SERV (1-800-426-7378).  
Hardware Service and Support  
You can receive hardware service through IBM Integrated Technology Services or through your IBM  
reseller, if your reseller is authorized by IBM to provide warranty service. Go to  
http://www.ibm.com/planetwide/ for support telephone numbers, or in the U.S. and Canada, call  
1-800-IBM-SERV (1-800-426-7378).  
In the U.S. and Canada, hardware service and support is available 24 hours a day, 7 days a week. In the  
U.K., these services are available Monday through Friday, from 9 a.m. to 6 p.m.  
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A P P E N D I X  
D
Notices  
This information was developed for products and services offered in the U.S.A.  
IBM may not offer the products, services, or features discussed in this document in other countries.  
Consult your local IBM representative for information on the products and services currently available  
in your area. Any reference to an IBM product, program, or service is not intended to state or imply that  
only that IBM product, program, or service may be used. Any functionally equivalent product, program,  
or service that does not infringe any IBM intellectual property right may be used instead. However, it is  
the user’s responsibility to evaluate and verify the operation of any non-IBM product, program, or  
service.  
IBM may have patents or pending patent applications covering subject matter described in this  
document. The furnishing of this document does not give you any license to these patents. You can send  
license inquiries, in writing, to:  
IBM Director of Licensing  
IBM Corporation  
North Castle Drive  
Armonk, NY 10504-1785  
U.S.A.  
INTERNATIONAL BUSINESS MACHINES CORPORATION PROVIDES THIS PUBLICATION  
“AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING,  
BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF NON-INFRINGEMENT,  
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Some states do not allow  
disclaimer of express or implied warranties in certain transactions, therefore, this statement may not  
apply to you.  
This information could include technical inaccuracies or typographical errors. Changes are periodically  
made to the information herein; these changes will be incorporated in new editions of the publication.  
IBM may make improvements and/or changes in the product(s) and/or the program(s) described in this  
publication at any time without notice.  
Any references in this information to non-IBM Web sites are provided for convenience only and do not  
in any manner serve as an endorsement of those Web sites. The materials at those Web sites are not part  
of the materials for this IBM product, and use of those Web sites is at your own risk.  
IBM may use or distribute any of the information you supply in any way it believes appropriate without  
incurring any obligation to you.  
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Appendix D Notices  
Edition Notice  
Edition Notice  
© Copyright International Business Machines Corporation 2004. All rights reserved.  
U.S. Government Users Restricted Rights — Use, duplication, or disclosure restricted by GSA ADP  
Schedule Contract with IBM Corp.  
Trademarks  
The following terms are trademarks of International Business Machines Corporation in the United  
States, other countries, or both:  
Active Memory  
Active PCI  
Active PCI-X  
Alert on LAN  
BladeCenter  
C2T Interconnect  
Chipkill  
Predictive Failure Analysis  
PS/2  
ServeRAID  
ServerGuide  
ServerProven  
TechConnect  
ThinkPad  
EtherJet  
Tivoli  
e-business logo  
Eserver  
Tivoli Enterprise  
Update Connector  
Wake on LAN  
XA-32  
FlashCopy  
IBM  
IBM (logo)  
IntelliStation  
NetBAY  
XA-64  
X-Architecture  
XceL4  
Netfinity  
XpandOnDemand  
xSeries  
NetView  
OS/2 WARP  
Cisco, Cisco IOS, Cisco Systems, the Cisco Systems logo, Catalyst, EtherChannel, IOS, IP/TV, Packet,  
and SwitchProbe are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United  
States and certain other countries.  
Intel, MMX, and Pentium are trademarks of Intel Corporation in the United States, other countries, or  
both.  
Microsoft, Windows, and Windows NT are trademarks of Microsoft Corporation in the United States,  
other countries, or both.  
Red Hat, the Red Hat “Shadow Man” logo, and all Red Hat-based trademarks and logos are trademarks  
or registered trademarks of Red Hat, Inc., in the United States and other countries.  
UNIX is a registered trademark of The Open Group in the United States and other countries.  
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Appendix D Notices  
Trademarks  
Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun  
Microsystems, Inc. in the United States, other countries, or both.  
Other company, product, or service names may be trademarks or service marks of others.  
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Appendix D Notices  
Trademarks  
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I N D E X  
any keyword 22-8  
Numerics  
applying  
802.1Q  
time ranges to 22-14  
to management interfaces 22-18  
to physical interfaces 22-19  
to QoS 23-5  
and trunk ports 7-2  
encapsulation 12-14  
to terminal lines 22-19  
classifying traffic for QoS 23-23  
comments in 22-16  
A
abbreviating commands 2-4  
access-class command 22-19  
access control entries  
See ACEs  
compiling 22-22  
configuration guidelines  
management interfaces, applying to 22-6  
physical interfaces, applying to 22-5  
defined 22-2  
access control lists  
See ACLs  
access control parameter  
See ACP  
displaying interface 22-21  
examples of 22-22  
access-denied response, VMPS 12-26  
access groups, viewing 22-21  
access lists  
extended IP  
configuring for QoS classification 23-25  
creating 22-9  
See ACLs  
matching criteria 22-7  
host keyword 22-8  
access ports defined 7-2  
accounting  
IP  
with IEEE 802.1x 6-5, 6-24  
with RADIUS 5-27  
with TACACS+ 5-10, 5-16  
ACEs  
creating 22-7  
implicit deny 22-9, 22-12, 22-14  
implicit masks 22-9  
management interfaces, applying to 22-18  
matching criteria 22-2, 22-7  
named 22-12  
defined 22-2  
Ethernet 22-2  
IP 22-2  
physical interfaces, applying to 22-19  
undefined 22-18, 22-20  
virtual terminal lines, setting on 22-19  
MAC extended 22-17  
Layer 3 parameters 22-9  
Layer 4 parameters 22-10  
ACLs  
ACEs 22-2  
matching 22-7  
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Index  
monitoring 22-20  
MAC address table 4-20  
maximum  
named 22-12  
numbers 22-7  
for MSTP 10-20  
protocol parameters 22-9  
standard IP  
for STP 9-22  
alarms, RMON 19-3  
allowed-VLAN list 12-19  
ARP table  
configuring for QoS classification 23-23  
creating 22-8  
matching criteria 22-7  
time ranges 22-14  
address resolution 4-24  
managing 4-24  
unsupported features 22-6  
attributes, RADIUS  
vendor-proprietary 5-29  
vendor-specific 5-28  
audience xxiii  
ACP  
system-defined mask 22-4  
understanding 22-4  
user-defined mask 22-4  
addresses  
authentication  
local mode with AAA 5-31  
NTP associations 4-4  
RADIUS  
displaying the MAC address table 4-24  
dynamic  
accelerated aging 9-8  
changing the aging time 4-20  
default aging 9-8  
defined 4-18  
defined 5-17  
key 5-20  
login 5-22  
TACACS+  
learning 4-19  
defined 5-10  
removing 4-20  
key 5-12  
MAC, discovering 4-24  
multicast STP address management 9-8  
static  
login 5-13  
See also port-based authentication  
authoritative time source, described 4-2  
authorization  
adding and removing 4-23  
defined 4-18  
with RADIUS 5-26  
with TACACS+ 5-10, 5-15  
authorized ports with IEEE 802.1x 6-4  
automatic QoS  
address resolution 4-24  
Address Resolution Protocol  
See ARP table  
advertisements  
See QoS  
CDP 17-1  
autonegotiation  
VTP 12-17, 13-3  
interface configuration guidelines 7-11  
mismatches 25-7  
aging, accelerating 9-8  
aging time  
accelerated  
for MSTP 10-19  
for STP 9-8, 9-22  
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Index  
B
C
BackboneFast  
cables, monitoring for unidirectional links 16-1  
caution, described xxiv  
CDP  
described 11-5  
enabling 11-14  
support for 1-3  
banners  
and trusted boundary 23-20  
configuring 17-2  
configuring  
default configuration 17-2  
described 17-1  
login 4-18  
message-of-the-day login 4-16  
default configuration 4-16  
when displayed 4-16  
booting  
disabling for routing device 17-3, 17-4  
enabling and disabling  
on an interface 17-4  
on a switch 17-3  
boot loader, function of 3-2  
boot process 3-1  
specific image 3-8  
boot loader  
monitoring 17-5  
overview 17-1  
transmission timer and holdtime, setting 17-2  
updates 17-2  
accessing 3-8  
Cisco Discovery Protocol  
See CDP  
described 3-2  
environment variables 3-8  
prompt 3-8  
CiscoWorks 2000 1-6, 21-4  
class maps for QoS  
configuring 23-27  
trap-door mechanism 3-2  
BPDU  
described 23-6  
error-disabled state 11-3  
filtering 11-3  
displaying 23-36  
class of service  
RSTP format 10-8  
BPDU filtering  
See CoS  
clearing interfaces 7-15  
CLI  
described 11-3  
enabling 11-12  
support for 1-3  
BPDU guard  
abbreviating commands 2-4  
command modes 2-1  
described 1-6  
described 11-3  
enabling 11-11  
support for 1-3  
broadcast storm control  
See storm control  
editing features  
enabling and disabling 2-6  
keystroke editing 2-7  
wrapped lines 2-8  
error messages 2-5  
getting help 2-3  
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Index  
CLI (continued)  
history  
uploading  
preparing B-10, B-13, B-16  
reasons for B-8  
changing the buffer size 2-5  
described 2-5  
using FTP B-14  
disabling 2-6  
using RCP B-18  
recalling commands 2-6  
no and default forms of commands 2-4  
client mode, VTP 13-3  
clock  
using TFTP B-12  
VMPS database 12-27  
configuration settings, saving 3-6  
configure terminal command 7-5  
config-vlan mode 2-2, 12-6  
connections, secure remote 5-32  
connectivity problems 25-7  
See system clock  
command-line interface  
See CLI  
command modes 2-1  
commands  
considerations, Cisco Systems Intelligent Gigabit Ethernet  
Switch Module 9-11  
consistency checks in VTP version 2 13-4  
console port, connecting to 2-9  
conventions  
abbreviating 2-4  
no and default 2-4  
setting privilege levels 5-7  
community strings  
command xxiv  
for examples xxiv  
configuring 21-7  
publication xxiv  
overview 21-4  
text xxiv  
config.text 3-7  
CoS  
configurable leave timer, IGMP 14-6  
configuration files  
configuring 23-7  
configuring priority queues 23-34  
defining 23-8  
clearing the startup configuration B-19  
creating using a text editor B-10  
default name 3-7  
described 1-5  
CoS-to-DSCP map for QoS 23-32  
counters, clearing interface 7-15  
crashinfo file 25-13  
deleting a stored configuration B-19  
downloading  
preparing B-10, B-13, B-16  
reasons for B-8  
using FTP B-13  
D
using RCP B-17  
daylight saving time 4-12  
debugging  
using TFTP B-11  
guidelines for creating and using B-9  
invalid combinations when copying B-5  
limiting TFTP server access 21-13  
specifying the filename 3-7  
system contact and location information 21-13  
types and location B-10  
enabling all system diagnostics 25-12  
enabling for a specific feature 25-11  
redirecting error message output 25-12  
using commands 25-11  
default commands 2-4  
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Index  
default configuration  
auto-QoS 23-9  
destination addresses, in ACLs 22-11  
destination-IP address-based forwarding,  
EtherChannel 24-7  
banners 4-16  
detecting indirect link failures, STP 11-6  
device discovery protocol 17-1  
device manager described 1-1, 1-6  
Differentiated Services architecture, QoS 23-2  
Differentiated Services Code Point 23-2  
directories  
booting 3-7  
CDP 17-2  
DNS 4-15  
EtherChannel 24-8  
IEEE 802.1x 6-11  
IGMP filtering 14-22  
IGMP snooping 14-8  
IGMP throttling 14-22  
initial switch information 3-2  
Layer 2 interfaces 7-9  
MAC address table 4-20  
MSTP 10-11  
changing B-4  
creating and removing B-4  
displaying the working B-4  
DNS  
default configuration 4-15  
displaying the configuration 4-16  
overview 4-14  
MVR 14-18  
setting up 4-15  
NTP 4-4  
documentation, related xxv  
document conventions xxiv  
domain names  
optional spanning-tree features 11-10  
password and privilege level 5-2  
port security 15-6  
QoS 23-16  
DNS 4-14  
VTP 13-8  
RADIUS 5-19  
Domain Name System  
See DNS  
RMON 19-3  
RSPAN 18-7  
downloading  
SNMP 21-5  
configuration files  
SPAN 18-7  
preparing B-10, B-13, B-16  
reasons for B-8  
storm control 15-2  
STP 9-12  
using FTP B-13  
system message logging 20-3  
system name and prompt 4-14  
TACACS+ 5-12  
using RCP B-17  
using TFTP B-11  
image files  
UDLD 16-4  
deleting old image B-23  
preparing B-21, B-24, B-28  
reasons for B-19  
VLAN, Layer 2 Ethernet interfaces 12-17  
VLANs 12-7  
VMPS 12-27  
using FTP B-25  
VTP 13-6  
using RCP B-29  
deleting VLANs 12-10  
denial-of-service attack 15-1  
description command 7-12  
using TFTP B-22  
using the device manager B-19  
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Index  
DSCP 1-5, 23-2  
EtherChannel  
DSCP-to-CoS map for QoS 23-33  
DTP 1-4, 12-15  
automatic creation of 24-3  
configuration guidelines 24-8  
default configuration 24-8  
destination MAC address forwarding 24-6  
displaying status 24-15  
forwarding methods 24-11  
interaction with STP 24-9  
Layer 2 interfaces, configuring 24-9  
load balancing 24-6, 24-11  
overview 24-1  
dynamic access ports  
characteristics 12-3  
configuring 12-28  
defined 7-2  
dynamic addresses  
See addresses  
dynamic desirable trunking mode 12-15  
dynamic port VLAN membership  
described 12-26  
PAgP  
reconfirming 12-29, 12-30  
troubleshooting 12-31  
types of connections 12-28  
VMPS database configuration file 12-27  
Dynamic Trunking Protocol  
See DTP  
aggregate-port learners 24-5  
compatibility with Catalyst 1900 24-12  
displaying status 24-15  
interaction with other features 24-5  
learn method and priority configuration 24-12  
modes 24-4  
overview 24-3  
silent mode 24-4  
E
support for 1-2  
port-channel interfaces  
described 24-2  
editing features  
enabling and disabling 2-6  
keystrokes used 2-7  
numbering of 24-2  
port groups 7-3  
wrapped lines 2-8  
source MAC address forwarding 24-6  
EtherChannel guard  
egress port scheduling 23-8  
enable password 5-4  
described 11-8  
enable secret password 5-4  
encapsulation 23-7  
enabling 11-15  
Ethernet VLANs  
encryption for passwords 5-4  
environment variables  
function of 3-10  
adding 12-8  
defaults and ranges 12-7  
modifying 12-8  
location in Flash 3-8  
events, RMON 19-3  
error messages  
examples  
during command entry 2-5  
setting the display destination device 20-4  
severity levels 20-8  
conventions for xxiv  
expedite queue, QoS 23-8  
extended-range VLANs  
configuration guidelines 12-12  
system message format 20-2  
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extended-range VLANs (continued)  
configuring 12-11  
forward-delay time  
MSTP 10-19  
creating 12-12  
STP 9-5, 9-22  
extended system ID  
forwarding  
MSTP 10-13  
See storm control  
FTP  
STP 9-4, 9-15  
Extensible Authentication Protocol over LAN 6-1  
accessing MIB files A-3  
configuration files  
downloading B-13  
overview B-12  
F
preparing the server B-13  
uploading B-14  
image files  
fallback VLAN name 12-27  
features, Cisco IOS 1-1  
fiber-optic, detecting unidirectional links 16-1  
files  
deleting old image B-27  
downloading B-25  
preparing the server B-24  
uploading B-27  
copying B-5  
deleting B-6  
displaying the contents of B-8  
tar  
creating B-6  
G
displaying the contents of B-7  
extracting B-7  
GBICs  
image file format B-20  
files, crashinfo  
security and identification 25-7  
get-bulk-request operation 21-3  
get-next-request operation 21-3, 21-4  
get-request operation 21-3, 21-4  
get-response operation 21-3  
global configuration mode 2-2  
guide  
description 25-13  
displaying the contents of 25-13  
location 25-13  
file system  
displaying available file systems B-2  
displaying file information B-3  
local file system names B-1  
network file system names B-5  
setting the default B-3  
filtering show and more command output 2-9  
filters, IP  
audience xxiii  
purpose of xxiii  
GUIs  
See device manager 1-6  
H
See ACLs, IP  
flash device, number of B-1  
flow-based packet classification 1-5  
hello time  
MSTP 10-18  
STP 9-21  
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help, for the command line 2-3  
history  
IGMP configurable leave timer, described 14-6  
IGMP filtering  
changing the buffer size 2-5  
described 2-5  
configuring 14-23  
default configuration 14-22  
described 14-22  
disabling 2-6  
recalling commands 2-6  
history table, level and number of syslog messages 20-10  
hosts, limit on dynamic ports 12-31  
HP OpenView 1-6  
monitoring 14-27  
IGMP groups  
configuring the throttling action 14-25  
setting the maximum number 14-25  
IGMP profile  
applying 14-24  
I
configuration mode 14-23  
configuring 14-23  
ICMP ping  
IGMP snooping  
executing 25-8  
configuring 14-7  
overview 25-8  
default configuration 14-8  
definition 14-2  
IDS, using with SPAN and RSPAN 18-2  
IEEE 802.1D  
enabling and disabling 14-8  
global configuration 14-8  
Immediate Leave 14-6  
method 14-9  
See STP  
IEEE 802.1Q  
configuration limitations 12-16  
native VLAN for untagged traffic 12-21  
IEEE 802.1s  
monitoring 14-14  
VLAN configuration 14-8  
IGMP throttling  
See MSTP  
IEEE 802.1w  
configuring 14-25  
See RSTP  
default configuration 14-22  
described 14-22  
IEEE 802.1x  
See port-based authentication  
IGMP  
displaying action 14-27  
Immediate-Leave, IGMP 14-6  
ingress port scheduling 23-8  
interface  
configurable leave timer, procedures 14-12  
joining multicast group 14-3  
join messages 14-3  
leave processing, enabling 14-11  
leaving multicast group 14-5  
queries 14-4  
number 7-4  
range macros 7-7  
interface command 7-4, 7-5  
interface configuration mode 2-3  
interfaces  
report suppression  
described 14-6  
Cisco IOS supported 1-6  
configuration guidelines 7-11  
configuring 7-5  
disabling 14-13  
throttling action 14-22  
IGMP, joining multicast group 14-3  
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interfaces (continued)  
configuring speed 7-11  
counters, clearing 7-15  
described 7-12  
IP addresses  
discovering 4-24  
ip igmp profile command 14-23  
IP information  
descriptive name, adding 7-12  
displaying information about 7-13  
monitoring 7-13  
assigned  
manually 3-3  
default configuration 3-2  
naming 7-12  
IP multicast routing and IGMP snooping 14-2, 14-7  
IP phones  
physical, identifying 7-4  
range of 7-6  
and IEEE 802.1x authentication 6-8  
automatic classification and queueing 23-9  
trusted boundary for QoS 23-20  
IP protocols in ACLs 22-11  
IPv4 1-1  
restarting 7-15  
shutting down 7-15  
supported 7-9  
types of 7-1  
interfaces range macro command 7-7  
Intrusion Detection System  
See IDS  
IPv6 1-1  
IP version 4 1-1  
IP version 6 1-1  
IOS command-line interface  
See CLI  
J
IP  
named extended ACL 22-13  
named standard ACL 22-13  
numbered extended ACL 22-9  
numbered standard ACL 22-8  
IP ACLs  
join messages, IGMP 14-3  
L
LACP  
applying to  
See EtherChannel  
management interfaces 22-18  
physical interfaces 22-19  
extended, creating 22-9  
for QoS classification 23-23  
implicit deny 22-9, 22-12, 22-14  
implicit masks 22-9  
Layer 2 frames, classification with CoS 23-2  
Layer 2 interfaces, default configuration 7-9  
Layer 2 traceroute  
and ARP 25-10  
and CDP 25-9  
described 25-9  
management interfaces, applying to 22-18  
named 22-12  
IP addresses and subnets 25-10  
MAC addresses and VLANs 25-10  
multicast traffic 25-10  
multiple devices on a port 25-10  
unicast traffic 25-9  
physical interfaces, applying to 22-19  
standard, creating 22-8  
undefined 22-18, 22-20  
virtual terminal lines, setting on 22-19  
usage guidelines 25-9  
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Layer 2 trunk failover  
configuration guidelines 24-17  
configuring 24-17  
static  
adding 4-23  
characteristics of 4-23  
removing 4-23  
default configuration 24-16  
described 24-15  
sticky secure, adding 15-5  
MAC address multicast entries, monitoring 14-15  
MAC address-to-VLAN mapping 12-26  
MAC extended access lists 22-17  
macros  
displaying status 24-18  
Layer 3 packets, classification methods 23-2  
Layer 3 parameters of ACEs 22-9  
Layer 4 parameters of ACEs 22-10  
leave processing, IGMP 14-11  
line configuration mode 2-3  
Link Aggregation Control Protocol  
See EtherChannel  
See Smartports macros  
magic packet 6-10  
management options  
CLI 2-1  
links, unidirectional 16-1  
login authentication  
overview 1-6  
mapping tables for QoS  
configuring  
with RADIUS 5-22  
with TACACS+ 5-13  
login banners 4-16  
DSCP 23-31  
DSCP-to-CoS 23-33  
described 23-5  
log messages  
See system message logging  
loop guard  
matching, ACLs 22-7  
maximum aging time  
MSTP 10-20  
described 11-9  
enabling 11-16  
STP 9-22  
support for 1-3  
maximum hop count, MSTP 10-20  
membership mode, VLAN port 12-3  
messages to users through banners 4-16  
MIBs  
M
accessing files with FTP A-3  
location of files A-3  
overview 21-1  
MAC addresses  
aging time 4-20  
and VLAN association 4-19  
building the address table 4-19  
default configuration 4-20  
discovering 4-24  
displaying 4-24  
SNMP interaction with 21-4  
supported A-1  
mirroring traffic for analysis 18-1  
mismatches, autonegotiation 25-7  
monitoring  
dynamic  
access groups 22-21  
ACLs 22-20  
learning 4-19  
removing 4-20  
cables for unidirectional links 16-1  
CDP 17-5  
in ACLs 22-17  
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monitoring (continued)  
IGMP  
CST defined 10-3  
default configuration 10-11  
default optional feature configuration 11-10  
described 10-2  
filters 14-27  
snooping 14-14  
interfaces 7-13  
displaying status 10-22  
enabling the mode 10-12  
EtherChannel guard  
multicast router ports 14-15  
MVR 14-21  
network traffic for analysis with probe 18-1  
port protection 15-11  
speed and duplex mode 7-12  
traffic flowing among switches 19-1  
traffic suppression 15-11  
VLANs 12-13  
described 11-8  
enabling 11-15  
extended system ID  
effects on root switch 10-13  
effects on secondary root switch 10-15  
unexpected behavior 10-14  
instances supported 9-9  
interface state, blocking to forwarding 11-2  
VMPS 12-30  
VTP 13-15  
MSTP  
interoperability and compatibility among modes 9-10  
interoperability with IEEE 802.1D  
described 10-4  
boundary ports  
configuration guidelines 10-12  
BPDU filtering  
restarting migration process 10-21  
IST  
described 11-3  
enabling 11-12  
defined 10-2  
BPDU guard  
operations within a region 10-3  
loop guard  
described 11-3  
enabling 11-11  
described 11-9  
CIST, described 10-3  
configuration guidelines 10-11, 11-10  
configuring  
enabling 11-16  
mapping VLANs to MST instance 10-12  
MST region  
forward-delay time 10-19  
hello time 10-18  
described 10-2  
hop-count mechanism 10-4  
supported spanning-tree instances 10-2  
Port Fast  
link type for rapid convergence 10-21  
maximum aging time 10-20  
maximum hop count 10-20  
MST region 10-12  
path cost 10-17  
described 11-2  
enabling 11-10  
preventing root switch selection 11-8  
root guard  
port priority 10-15  
root switch 10-13  
described 11-8  
secondary root switch 10-15  
switch priority 10-18  
enabling 11-15  
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MSTP (continued)  
Network Time Protocol  
See NTP  
root switch  
configuring 10-14  
no commands 2-4  
nontrunking mode 12-15  
normal-range VLANs  
configuration modes 12-6  
defined 12-1  
effects of extended system ID 10-13  
unexpected behavior 10-14  
shutdown Port Fast-enabled port 11-3  
multicast groups  
and IGMP snooping 14-7  
Immediate Leave 14-6  
joining 14-3  
note, described xxiv  
NTP  
associations  
leaving 14-5  
authenticating 4-4  
defined 4-2  
static joins 14-10  
multicast router ports  
adding 14-10  
enabling broadcast messages 4-6  
peer 4-5  
monitoring 14-15  
server 4-5  
multicast storm control  
See storm control  
default configuration 4-4  
displaying the configuration 4-10  
overview 4-2  
Multicast VLAN Registration  
See MVR  
restricting access  
Multiple Spanning Tree Protocol  
See MSTP  
creating an access group 4-8  
disabling NTP services per interface 4-9  
source IP address, configuring 4-9  
stratum 4-2  
MVR  
configuring interfaces 14-20  
default configuration 14-18  
described 14-15  
synchronizing devices 4-5  
time  
modes 14-19  
services 4-2  
monitoring 14-21  
synchronizing 4-2  
setting global parameters 14-18  
O
N
out-of-profile markdown 1-5  
named IP ACLs 22-12  
native VLAN  
P
configuring 12-21  
default 12-21  
PAgP  
network management  
CDP 17-1  
See EtherChannel  
pass-through mode 23-22  
RMON 19-1  
SNMP 21-1  
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passwords  
defined 6-2  
default configuration 5-2  
encrypting 5-4  
RADIUS server 6-2  
client, defined 6-2  
overview 5-1  
configuration guidelines 6-12  
configuring  
recovery of 25-2  
setting  
guest VLAN 6-20  
enable 5-3  
host mode 6-20  
enable secret 5-4  
Telnet 5-5  
IEEE 802.1x accounting 6-24  
IEEE 802.1x authentication 6-13, 6-22  
manual re-authentication of a client 6-17  
periodic re-authentication 6-16  
quiet period 6-17  
with usernames 5-6  
VTP domain 13-8  
path cost  
MSTP 10-17  
RADIUS server 6-15  
STP 9-19  
RADIUS server parameters on the switch 6-14  
switch-to-client frame-retransmission number 6-19  
switch-to-client retransmission time 6-18  
default configuration 6-11  
described 6-1  
per-VLAN spanning-tree plus  
See PVST+  
physical ports 7-1  
PIM-DVMRP, as snooping method 14-9  
ping  
device roles 6-2  
character output description 25-9  
executing 25-8  
displaying statistics 6-25  
EAPOL-start frame 6-3  
overview 25-8  
EAP-request/identity frame 6-3  
EAP-response/identity frame 6-3  
enabling  
policers  
configuring for each matched traffic class 23-28  
described 23-3  
IEEE 802.1x with guest VLAN 6-9  
IEEE 802.1x with port security 6-7  
IEEE 802.1x with VLAN assignment 6-8, 6-13  
IEEE 802.1x with voice VLAN 6-8  
encapsulation 6-3  
number of 1-5, 23-6  
types of 23-6  
policing 1-5, 23-3  
policy maps for QoS  
characteristics of 23-28  
configuring 23-28  
described 23-6  
guest VLAN  
configuration guidelines 6-10  
host mode 6-6  
displaying 23-36  
Port Aggregation Protocol  
See EtherChannel  
port-based authentication  
accounting 6-5  
initiation and message exchange 6-3  
magic packet 6-10  
method lists 6-13, 6-22  
multiple-hosts mode, described 6-6  
accounting services 1-4  
authentication server  
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port-based authentication (continued)  
ports  
displaying 15-11  
sticky learning 15-5  
violations 15-5  
authorization state and dot1x port-control  
command 6-4  
with other features 15-6  
port-shutdown response, VMPS 12-26  
preferential treatment of traffic  
See QoS  
authorized and unauthorized 6-4  
port security, multiple-hosts mode 6-6  
resetting to default values 6-22  
switch  
preventing unauthorized access 5-1  
priority  
as proxy 6-2  
RADIUS client 6-3  
VLAN assignment, AAA authorization 6-22  
wake-on-LAN, described 6-10  
port-channel  
port, described 23-7  
private VLAN edge ports  
See protected ports  
privileged EXEC mode 2-2  
privilege levels  
See EtherChannel  
Port Fast  
changing the default for lines 5-8  
exiting 5-8  
described 11-2  
enabling 11-10  
logging into 5-8  
mode, spanning tree 12-27  
support for 1-3  
overview 5-2, 5-6  
setting a command with 5-7  
protected ports 1-2, 15-3  
pruning, VTP  
port membership modes, VLAN 12-3  
port priority  
MSTP 10-15  
enabling 13-13  
STP 9-17  
enabling on a port 12-20  
examples 13-5  
ports  
dynamic access 12-3  
priority 23-7  
overview 13-4  
pruning-eligible list  
changing 12-20  
protected 15-3  
secure 15-4  
for VTP pruning 13-5  
VLANs 13-13  
static-access 12-3, 12-10  
switch 7-1, 7-5  
publications, related xxv  
PVST+  
trunks 12-14  
VLAN assignments 12-10  
port scheduling 23-8  
port security  
described 9-9  
IEEE 802.1Q trunking interoperability 9-10  
instances supported 9-9  
aging 15-9  
configuration guidelines 15-6  
configuring 15-7  
default configuration 15-6  
described 15-4  
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auto-QoS 23-9  
Q
class maps 23-27  
QoS  
CoS and WRR 23-34  
default port CoS value 23-19  
egress queues 23-34  
IP extended ACLs 23-25  
IP standard ACLs 23-23  
MAC ACLs 23-26  
and MQC commands 23-1  
auto-QoS  
categorizing traffic 23-9  
configuration and defaults display 23-13  
configuration guidelines 23-11  
described 23-9  
policy maps 23-28  
displaying 23-13  
port trust states within the domain 23-18  
QoS policy 23-23  
effects on NVRAM configuration 23-11  
egress queue defaults 23-10  
enabling for VoIP 23-12  
example, configuration 23-14  
generated commands 23-10  
basic model 23-3  
trusted boundary 23-21  
default auto configuration 23-9  
default configuration 23-16  
described 23-2  
displaying statistics 23-36  
egress port scheduling 23-8  
enabling expedite queue 23-35  
expedite queue  
classification  
class maps, described 23-6  
defined 23-3  
in frames and packets 23-3  
IP ACLs, described 23-5  
MAC ACLs, described 23-5  
pass-through mode, described 23-22  
policy maps, described 23-6  
port default, described 23-4  
trust DSCP, described 23-4  
trusted boundary, described 23-20  
trusted CoS, described 23-4  
types for IP traffic 23-5  
types for non-IP traffic 23-4  
class maps  
described 23-8  
enabling 23-35  
ingress port scheduling 23-8  
IP phones  
automatic classification and queueing 23-9  
detection and trusted settings 23-9, 23-20  
mapping tables  
CoS-to-DSCP 23-32  
displaying 23-36  
DSCP-to-CoS 23-33  
types of 23-5  
marked-down actions 23-30  
marking, described 23-3, 23-6  
pass-through mode 23-22  
policers  
configuring 23-27  
displaying 23-36  
configuration examples  
auto-QoS 23-14  
configuring 23-30  
common wiring closet 23-37  
intelligent wiring closet 23-38  
configuration guidelines 23-16  
configuring  
described 23-6  
number of 23-6  
types of 23-6  
policing, described 23-3, 23-6  
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QoS (continued)  
policy maps  
range  
macro 7-7  
characteristics of 23-28  
of interfaces 7-6  
rapid convergence 10-6  
rapid per-VLAN spanning-tree plus  
See rapid PVST+  
configuring 23-28  
displaying 23-36  
queueing, defined 23-4  
scheduling, defined 23-4  
support for 1-5  
rapid PVST+  
described 9-9  
trusted boundary 23-20  
trust states 23-4  
IEEE 802.1Q trunking interoperability 9-10  
instances supported 9-9  
rapid-PVST+ 12-2  
Rapid Spanning Tree Protocol  
See RSTP  
understanding 23-2  
quality of service  
See QoS  
queries, IGMP 14-4  
RCP  
configuration files  
downloading B-17  
overview B-15  
R
preparing the server B-16  
uploading B-18  
RADIUS  
attributes  
image files  
vendor-proprietary 5-29  
vendor-specific 5-28  
deleting old image B-31  
downloading B-29  
preparing the server B-28  
uploading B-31  
configuring  
accounting 5-27  
authentication 5-22  
reconfirmation interval, VMPS, changing 12-30  
recovery procedures 25-1  
redundancy  
authorization 5-26  
communication, global 5-20, 5-28  
communication, per-server 5-19, 5-20  
multiple UDP ports 5-20  
default configuration 5-19  
defining AAA server groups 5-24  
described 5-17  
EtherChannel 24-2  
STP  
backbone 9-8  
path cost 12-24  
port priority 12-22  
displaying the configuration 5-30  
identifying the server 5-19  
limiting the services to the user 5-26  
method list, defined 5-19  
operation of 5-18  
redundant links and UplinkFast 11-13  
reloading software 3-11  
Remote Authentication Dial-In User Service  
See RADIUS  
Remote Copy Protocol  
See RCP  
suggested network environments 5-17  
tracking services accessed by user 5-27  
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remote monitoring  
root switch  
see RMON  
MSTP 10-13  
Remote Network Monitoring  
See RMON  
STP 9-15  
RSPAN  
report suppression, IGMP  
described 14-6  
configuration guidelines 18-12  
default configuration 18-7  
destination ports 18-4  
displaying status 18-17  
IDS 18-2  
disabling 14-13  
resetting a UDLD-shutdown interface 16-6  
restricting access  
NTP services 4-7  
interaction with other features 18-6  
monitored ports 18-4  
monitoring ports 18-4  
overview 1-5, 18-1  
overview 5-1  
passwords and privilege levels 5-2  
RADIUS 5-16  
TACACS+ 5-9  
received traffic 18-3  
reflector port 18-5  
retry count, VMPS, changing 12-30  
RFC  
session limits 18-7  
sessions  
1112, IP multicast and IGMP 14-2  
1157, SNMPv1 21-2  
1305, NTP 4-2  
creating 18-13  
defined 18-3  
1757, RMON 19-2  
1901, SNMPv2C 21-2  
1902 to 1907, SNMPv2 21-2  
2236, IP multicast and IGMP 14-2  
2273-2275, SNMPv3 21-2  
RMON  
removing source (monitored) ports 18-16  
specifying monitored ports 18-13  
source ports 18-4  
transmitted traffic 18-3  
RSTP  
active topology, determining 10-5  
BPDU  
default configuration 19-3  
displaying status 19-6  
enabling alarms and events 19-3  
groups supported 19-2  
overview 19-1  
format 10-8  
processing 10-9  
designated port, defined 10-5  
designated switch, defined 10-5  
interoperability with IEEE 802.1D  
described 10-4  
statistics  
collecting group Ethernet 19-5  
collecting group history 19-5  
root guard  
restarting migration process 10-21  
topology changes 10-9  
overview 10-5  
described 11-8  
enabling 11-15  
port roles  
support for 1-3  
described 10-5  
synchronized 10-7  
proposal-agreement handshake process 10-6  
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RSTP (continued)  
creating 8-4  
rapid convergence  
default configuration 8-2  
defined 8-1  
described 10-6  
edge ports and Port Fast 10-6  
point-to-point links 10-6, 10-21  
root ports 10-6  
displaying 8-8  
tracing 8-3  
website 8-2  
root port, defined 10-5  
See also MSTP  
SNAP 17-1  
SNMP  
running configuration, saving 3-4  
accessing MIB variables with 21-4  
agent  
described 21-3  
S
disabling 21-6  
community strings  
configuring 21-7  
scheduled reloads 3-11  
secure ports, configuring 15-4  
secure remote connections 5-32  
Secure Shell  
overview 21-4  
configuration examples 21-14  
default configuration 21-5  
groups 21-8  
See SSH  
security, port 15-4  
informs  
sequence numbers in log messages 20-8  
server mode, VTP 13-3  
and trap keyword 21-10  
described 21-4  
service-provider network, MSTP and RSTP 10-1  
set-request operation 21-4  
differences from traps 21-5  
enabling 21-12  
severity levels, defining in system messages 20-8  
show and more command output, filtering 2-9  
show cdp traffic command 17-5  
show configuration command 7-12  
show interfaces command 7-12  
show running-config command  
displaying ACLs 22-18, 22-19, 22-20  
interface description in 7-12  
shutdown command on interfaces 7-15  
Simple Network Management Protocol  
See SNMP  
limiting access by TFTP servers 21-13  
limiting system log messages to NMS 20-10  
manager functions 21-3  
MIBs  
location of A-3  
supported A-1  
notifications 21-4  
overview 21-1, 21-4  
status, displaying 21-15  
system contact and location 21-13  
trap manager, configuring 21-11  
traps  
Smartports macros  
applying Cisco-default macros 8-6  
applying global parameter values 8-5, 8-6  
applying macros 8-5  
described 21-3, 21-4  
differences from informs 21-5  
enabling 21-10  
applying parameter values 8-5, 8-7  
configuration guidelines 8-2  
enabling MAC address notification 4-21  
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SNMP (continued)  
spanning tree and native VLANs 12-16  
Spanning Tree Protocol  
See STP  
overview 21-1, 21-4  
types of 21-10  
users 21-8  
speed  
versions supported 21-2  
snooping, IGMP 14-2  
software images  
configuring on interfaces 7-11  
SSH  
configuring 5-33  
location in flash B-20  
recovery procedures 25-1  
scheduling reloads 3-11  
tar file format, described B-20  
See also downloading and uploading  
source addresses, in ACLs 22-11  
cryptographic software image 5-32  
described 5-32  
encryption methods 5-32  
user authentication methods, supported 5-33  
startup configuration  
booting  
source-and-destination-IP address based forwarding,  
specific image 3-8  
clearing B-19  
EtherChannel 24-7  
source-and-destination MAC address forwarding,  
configuration file  
EtherChannel 24-7  
specifying the filename 3-7  
default boot configuration 3-7  
static access ports  
source-IP address based forwarding, EtherChannel 24-7  
SPAN  
configuration guidelines 18-7  
default configuration 18-7  
destination ports 18-4  
displaying status 18-17  
IDS 18-2  
assigning to VLAN 12-10  
defined 7-2, 12-3  
static addresses  
See addresses  
static VLAN membership 12-2  
statistics  
interaction with other features 18-6  
monitored ports 18-4  
CDP 17-5  
monitoring ports 18-4  
overview 1-5, 18-1  
IEEE 802.1x 6-25  
interface 7-13  
ports, restrictions 15-7  
received traffic 18-3  
QoS ingress and egress 23-36  
RMON group Ethernet 19-5  
RMON group history 19-5  
SNMP input and output 21-15  
VTP 13-15  
session limits 18-7  
sessions  
creating 18-8  
defined 18-3  
sticky learning  
removing destination (monitoring) ports 18-11  
removing source (monitored) ports 18-11  
specifying monitored ports 18-8  
source ports 18-4  
configuration file 15-5  
defined 15-5  
disabling 15-5  
enabling 15-5  
transmitted traffic 18-3  
saving addresses 15-5  
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storm control  
EtherChannel guard  
configuring 15-2  
described 11-8  
default configuration 15-2  
described 15-1  
enabling 11-15  
extended system ID  
disabling 15-3  
affects on root switch 9-15  
affects on the secondary root switch 9-17  
overview 9-4  
displaying 15-11  
STP  
accelerating root port selection 11-4  
BackboneFast  
unexpected behavior 9-15  
features supported 1-3  
inferior BPDU 9-3  
described 11-5  
enabling 11-14  
instances supported 9-9  
interface state, blocking to forwarding 11-2  
interface states  
BPDU filtering  
described 11-3  
enabling 11-12  
blocking 9-5  
BPDU guard  
disabled 9-7  
described 11-3  
forwarding 9-5, 9-6  
enabling 11-11  
learning 9-6  
BPDU message exchange 9-3  
configuration guidelines 9-12, 11-10  
configuring  
listening 9-6  
overview 9-4  
interoperability and compatibility among modes 9-10  
limitations with IEEE 802.1Q trunks 9-10  
load sharing  
forward-delay time 9-22  
hello time 9-21  
maximum aging time 9-22  
path cost 9-19  
overview 12-22  
using path costs 12-24  
using port priorities 12-22  
loop guard  
port priority 9-17  
root switch 9-15  
secondary root switch 9-17  
spanning-tree mode 9-13  
switch priority 9-20  
counters, clearing 9-23  
default configuration 9-12  
default optional feature configuration 11-10  
designated port, defined 9-3  
designated switch, defined 9-3  
detecting indirect link failures 11-6  
disabling 9-14  
described 11-9  
enabling 11-16  
modes supported 9-9  
multicast addresses, affect of 9-8  
overview 9-2  
path costs 12-24  
Port Fast  
described 11-2  
enabling 11-10  
port priorities 12-23  
preventing root switch selection 11-8  
protocols supported 9-9  
redundant connectivity 9-8  
displaying status 9-23  
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STP (continued)  
disabling 20-4  
root guard  
displaying the configuration 20-12  
enabling 20-4  
described 11-8  
enabling 11-15  
facility keywords, described 20-12  
level keywords, described 20-9  
limiting messages 20-10  
message format 20-2  
root port, defined 9-3  
root switch  
affects of extended system ID 9-4, 9-15  
configuring 9-15  
overview 20-1  
election 9-3  
sequence numbers, enabling and disabling 20-8  
setting the display destination device 20-4  
synchronizing log messages 20-6  
timestamps, enabling and disabling 20-7  
UNIX syslog servers  
unexpected behavior 9-15  
shutdown Port Fast-enabled port 11-3  
superior BPDU 9-3  
timers, described 9-21  
UplinkFast  
configuring the daemon 20-11  
configuring the logging facility 20-11  
facilities supported 20-12  
system name  
described 11-4  
enabling 11-13  
stratum, NTP 4-2  
summer time 4-12  
SunNet Manager 1-6  
switched ports 7-1  
switchport protected command 15-4  
switch ports 7-5  
default configuration 4-14  
default setting 4-14  
manual configuration 4-14  
See also DNS  
system prompt  
switch priority  
default setting 4-13, 4-14  
MSTP 10-18  
STP 9-20  
T
syslog  
See system message logging  
system clock  
TACACS+  
accounting, defined 5-10  
authentication, defined 5-10  
authorization, defined 5-10  
configuring  
configuring  
daylight saving time 4-12  
manually 4-10  
summer time 4-12  
time zones 4-11  
accounting 5-16  
authentication key 5-12  
authorization 5-15  
displaying the time and date 4-11  
overview 4-1  
login authentication 5-13  
default configuration 5-12  
displaying the configuration 5-16  
identifying the server 5-12  
limiting the services to the user 5-15  
See also NTP  
system message logging  
default configuration 20-3  
defining error message severity levels 20-8  
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operation of 5-11  
described 25-9  
overview 5-9  
IP addresses and subnets 25-10  
MAC addresses and VLANs 25-10  
multicast traffic 25-10  
multiple devices on a port 25-10  
unicast traffic 25-9  
tracking services accessed by user 5-16  
tar files  
creating B-6  
displaying the contents of B-7  
extracting B-7  
usage guidelines 25-9  
trademarks D-2  
image file format B-20  
Telnet  
traffic  
accessing management interfaces 2-9  
accessing the CLI 1-6  
setting a password 5-5  
Terminal Access Controller Access Control System Plus  
See TACACS+  
fragmented 22-3  
unfragmented 22-3  
traffic policing 1-5  
transparent mode, VTP 13-3, 13-11  
trap-door mechanism 3-2  
traps  
terminal lines, setting a password 5-5  
TFTP  
configuring MAC address notification 4-21  
configuring managers 21-10  
defined 21-3  
configuration files  
downloading B-11  
preparing the server B-10  
uploading B-12  
enabling 4-21, 21-10  
notification types 21-10  
overview 21-1, 21-4  
image files  
deleting B-23  
troubleshooting  
downloading B-22  
connectivity problems 25-7  
detecting unidirectional links 16-1  
displaying crash information 25-13  
GBIC security and identification 25-7  
with CiscoWorks 21-4  
with debug commands 25-11  
with ping 25-8  
preparing the server B-21  
uploading B-23  
limiting access by servers 21-13  
time  
See NTP and system clock  
time-range command 22-14  
time ranges in ACLs 22-14  
timestamps in log messages 20-7  
time zones 4-11  
with system message logging 20-1  
trunk ports  
configuring 12-18  
Token Ring VLANs  
support for 12-5  
defined 7-2  
trunks  
VTP support 13-4  
allowed-VLAN list 12-19  
load sharing  
TOS 1-5  
traceroute, Layer 2  
setting STP path costs 12-24  
using STP port priorities 12-22, 12-23  
native VLAN for untagged traffic 12-21  
and ARP 25-10  
and CDP 25-9  
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trunks (continued)  
uploading  
parallel 12-24  
configuration files  
preparing B-10, B-13, B-16  
reasons for B-8  
pruning-eligible list 12-20  
to non-DTP device 12-15  
VLAN 1 minimization 12-19  
trusted boundary 23-20  
twisted-pair Ethernet, detecting unidirectional links 16-1  
type-of-service  
using FTP B-14  
using RCP B-18  
using TFTP B-12  
image files  
See TOS  
preparing B-21, B-24, B-28  
reasons for B-19  
using FTP B-27  
U
using RCP B-31  
using TFTP B-23  
user EXEC mode 2-2  
username-based authentication 5-6  
UDLD  
default configuration 16-4  
echoing detection mechanism 16-3  
enabling  
globally 16-5  
V
per interface 16-6  
link-detection mechanism 16-1  
neighbor database 16-2  
overview 16-1  
version-dependent transparent mode 13-4  
vlan.dat file 12-4  
VLAN 1 minimization, support for 1-4  
VLAN configuration  
resetting an interface 16-6  
status, displaying 16-7  
unauthorized ports with IEEE 802.1x 6-4  
unicast storm control  
at bootup 12-7  
saving 12-7  
VLAN configuration mode 2-2, 12-6  
VLAN database  
See storm control  
UniDirectional Link Detection protocol  
See UDLD  
and startup configuration file 12-7  
and VTP 13-1  
UNIX syslog servers  
VLAN configuration saved in 12-7  
VLANs saved in 12-4  
daemon configuration 20-11  
facilities supported 20-12  
message logging configuration 20-11  
unrecognized Type-Length-Value (TLV) support 13-4  
upgrading software images  
See downloading  
vlan database command 12-6  
vlan global configuration command 12-6  
VLAN ID, discovering 4-24  
VLAN management domain 13-2  
VLAN Management Policy Server  
See VMPS  
UplinkFast  
described 11-4  
VLAN membership  
enabling 11-13  
confirming 12-29  
support for 1-3  
modes 12-3  
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VLAN Query Protocol  
See VQP  
description 12-25  
dynamic port membership  
described 12-26  
VLANs  
adding 12-8  
reconfirming 12-30  
adding to VLAN database 12-8  
aging dynamic addresses 9-9  
allowed on trunk 12-19  
and spanning-tree instances 12-2, 12-6, 12-12  
configuration guidelines, normal-range VLANs 12-5  
configuration options 12-6  
configuring 12-1  
troubleshooting 12-31  
mapping MAC addresses to VLANs 12-26  
monitoring 12-30  
reconfirmation interval, changing 12-30  
reconfirming membership 12-29  
retry count, changing 12-30  
VQP 12-25  
configuring IDs 1006 to 4094 12-12  
creating in config-vlan mode 12-8  
creating in VLAN configuration mode 12-9  
default configuration 12-7  
deleting 12-10  
VTP  
adding a client to a domain 13-14  
advertisements 12-17, 13-3  
and extended-range VLANs 13-1  
and normal-range VLANs 13-1  
client mode, configuring 13-10  
configuration  
described 7-3, 12-1  
displaying 12-13  
extended-range 12-11  
illustrated 12-2  
global configuration mode 13-7  
guidelines 13-8  
modifying 12-8  
privileged EXEC mode 13-7  
requirements 13-9  
native, configuring 12-21  
normal-range 12-1, 12-4  
parameters 12-4  
saving 13-7  
VLAN configuration mode 13-7  
configuration mode options 13-7  
configuration requirements 13-9  
configuration revision number  
guideline 13-14  
port membership modes 12-3  
static-access ports 12-10  
STP and IEEE 802.1Q trunks 9-10  
supported 12-2  
Token Ring 12-5  
resetting 13-14  
trunks, VLAN 1 minimization 12-19  
VTP modes 13-3  
configuring  
client mode 13-10  
VLAN Trunking Protocol  
See VTP  
server mode 13-9  
transparent mode 13-11  
consistency checks 13-4  
default configuration 13-6  
described 13-1  
VLAN trunks 12-14  
VMPS  
administering 12-30  
configuration example 12-31  
configuration guidelines 12-27  
default configuration 12-27  
disabling 13-11  
domain names 13-8  
domains 13-2  
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VTP (continued)  
modes  
X
Xmodem protocol 25-1  
client 13-3, 13-10  
server 13-3, 13-9  
transitions 13-3  
transparent 13-3, 13-11  
monitoring 13-15  
passwords 13-8  
pruning  
disabling 13-13  
enabling 13-13  
examples 13-5  
overview 13-4  
pruning-eligible list, changing 12-20  
server mode, configuring 13-9  
statistics 13-15  
Token Ring support 13-4  
transparent mode, configuring 13-11  
using 13-1  
version, guidelines 13-8  
version 1 13-4  
version 2  
configuration guidelines 13-8  
disabling 13-13  
enabling 13-12  
overview 13-4  
W
Weighted Round Robin  
See WRR  
WRR  
configuring 23-35  
defining 23-8  
description 23-8  
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