Configuring the router mac address assignment – Cisco 6500 User Manual

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Cisco IOS Software Configuration Guide, Release 12.2SX

OL-13013-06

Chapter 4 Configuring Virtual Switching Systems

Configuring a VSS

Configuring the Router MAC Address Assignment

When the VSS is started for the first time, the initial VSS active supervisor engine assigns a router MAC
address for the VSS. By default, the supervisor engine assigns a MAC address from its own chassis.
After a switchover to the second chassis, the VSS continues to use the MAC address from the previously
VSS active chassis as the router MAC address.

In the rare case where both chassis later become inactive, and then they start up with the second
supervisor engine becoming the initial VSS active supervisor engine, the VSS will start up with a router
MAC address from the second chassis. Other Layer 2 hosts that do not respond to GARP and are not
directly connected to the VSS will retain the earlier router MAC address of the VSS, and will not be able
to communicate with the VSS. To avoid this possibility, you can configure the VSS to assign a router
MAC address from a reserved pool of addresses with the domain ID encoded in the last octet of the MAC
address, or you can specify a MAC address.

Note

If you change the router MAC address, you must reload the virtual switch for the new router MAC
address to take effect.

To specify that the router MAC address is assigned from a reserved pool of domain-based addresses,
perform this task:

To specify a router MAC address, perform this task:

This example shows how to configure router MAC address assignment from a reserved pool of
domain-based addresses:

Router(config)# switch virtual domain 255

Router(config-vs-domain)# mac-address use-virtual

The following example shows how to specify the router MAC address in hexadecimal format:

Router(config)# switch virtual domain 255

Router(config-vs-domain)# mac-address 0123.4567.89ab

Command

Purpose

Step 1

Router(config)# switch virtual domain domain_id

Enters VSS configuration mode.

Step 2

Router(config-vs-domain)# mac-address use-virtual

The router MAC address is assigned from a reserved
pool of domain-based addresses.