Cisco catalyst 3750 Command Reference Manual page 844

stack-mac persistent timer
You can set the time period to be from 0 to 60 minutes.
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Note When you enter the stack-mac persistent timer command with or without keywords, a message appears
warning that traffic might be lost if the old master MAC address appears elsewhere in the network
domain. You should use this feature cautiously.
If you enter the no stack-mac persistent timer command after a switchover, before the time expires,
the switch stack moves to the current stack master MAC address.
If the whole stack reloads, when it comes back up, the MAC address of the stack master is the stack MAC
address.
Examples This example shows how to configure the persistent MAC address feature, with the warning messages
for each configuration. It also shows how to verify the configuration:
Switch(config)# stack-mac persistent timer
WARNING: Use of an explicit timer value with the command is recommended
WARNING: Default value of 4 minutes is being used.
WARNING: The stack continues to use the base MAC of the old Master
WARNING: as the stack MAC after a master switchover until the MAC
WARNING: persistency timer expires. During this time the Network
WARNING: Administrators must make sure that the old stack-mac does
WARNING: not appear elsewhere in this network domain. If it does,
WARNING: user traffic may be blackholed.
Switch(config)# stack-mac persistent timer 0
WARNING: Stack MAC persistency timer value of 0 means that, after a
WARNING: master switchover, the current stack-mac will continue
WARNING: to be used indefinitely.
WARNING: The Network Administrators must make sure that the old
WARNING: stack-mac does not appear elsewhere in this network
WARNING: domain. If it does, user traffic may be blackholed.
Switch(config)# stack-mac persistent timer 7
WARNING: The stack continues to use the base MAC of the old Master
WARNING: as the stack MAC after a master switchover until the MAC
WARNING: persistency timer expires. During this time the Network
WARNING: Administrators must make sure that the old stack-mac does
WARNING: not appear elsewhere in this network domain. If it does,
WARNING: user traffic may be blackholed.
Switch(config)# end
Switch# show switch
Switch/Stack Mac Address : 0016.4727.a900
Mac persistency wait time: 7 mins
Switch#
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Catalyst 3750 Switch Command Reference
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If you enter the command with no value, the default delay is 4 minutes.
If you enter 0, the stack continues to use the current stack MAC address until you enter the no
stack-mac persistent timer command.
If you enter a time delay of 1 to 60 minutes, the stack MAC address of the previous stack master is
used until the configured time period expires or until you enter the no stack-mac persistent timer
command.
Role Mac Address
Master 0016.4727.a900
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
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