Switch Stack Bridge ID and MAC Address A switch stack is identified in the network by its bridge ID and, if it is operating as a Layer 3 device, its router MAC address. The bridge ID and router MAC address are determined by the MAC address of the active switch. If the active switch changes, the MAC address of the new active switch determines the new bridge ID and router MAC address. If the entire switch stack reloads, the switch stack uses the MAC address of the active switch. Persistent MAC Address on the Switch Stack You can use the persistent MAC address feature to set a time delay before the stack MAC address changes.
During this time period, if the previous active switch 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 an active switch. If the previous active switch does not rejoin the stack during this period, the switch stack takes the MAC address of the new active switch as the stack MAC address. By default, the stack MAC address will be the MAC address of the first active switch, even if a new active switch takes over. You can also configure stack MAC persistency so that the stack MAC address never changes to the new active switch MAC address, by using the stack-mac persistent timer 0 command.
Note Active 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. The active switch is elected or reelected based on one of these factors and in the order listed: 1. The switch that is currently the active switch. 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 switch. This ensures that the switch is reelected as active switch if a reelection occurs. Note 3. The switch with the shortest start-up time. Managing Switch Stacks Switch Stack Bridge ID and MAC Address Managing Switch Stacks 5