Cisco Catalyst 2960 Series, Configuration Manual

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You can use the persistent MAC address feature to set a time delay before the stack MAC address changes
to the MAC address of the new stack master. When this feature is enabled, the stack MAC address changes
in approximately 4 minutes. During this time, if the previous stack master rejoins the stack, the stack continues
to use its MAC address as the stack MAC address, even if the switch is now a stack member and not a stack
master. If the previous stack master does not rejoin the stack during this period, the switch stack takes the
MAC address of the new stack master as the stack MAC address.
You can also configure stack MAC persistency so that the stack MAC address never changes to the new active
switchstack master MAC address.
Stack MasterActive and Standby Switch Election and Reelection
All stack members are eligible to be the active switch or the standby switch. If the active switch becomes
unavailable, the standby switch becomes the active switch.
An active switch retains its role unless one of these events occurs:
• The switch stack is reset.
• The active switch is removed from the switch stack.
• The active switch is reset or powered off.
• The active switch fails.
• The switch stack membership is increased by adding powered-on standalone switches or switch stacks.
All stack members are eligible stack masters. If the stack master becomes unavailable, the remaining members
elect a new stack master from among themselves.
The active switchstack master is elected or reelected based on one of these factors and in the order listed:
1 The switch that is currently the active switchstack master.
2 The switch with the highest stack member priority value.
We recommend assigning the highest priority value to the switch that you prefer to be the active switchstack
master. This ensures that the switch is reelected as active switchstack master if a reelection occurs.
Note
3 The switch with the shortest start-up time.
4 The switch that has the configuration file.
5
The switch with the lowest MAC address.
The factors for electing or reelecting a new standby switch are same as those for the active switch election
or reelection, and are applied to all participating switches except the active switch.
Note
After election, the new active switch becomes available after a few seconds. In the meantime, the switch stack
uses the forwarding tables in memory to minimize network disruption. The physical interfaces on the other
available stack members are not affected during a new active switch election and reset.
When the previous active switch becomes available, it does not resume its role as the active switch.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
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Information About Switch Stacks