These rules have been defined to determine which unit within a stack is chosen as the master. When switches are added or stacks are merged, the master will be chosen based on these rules, in the order specified:

  1. The switch that is currently the stack master

    Note: When stacks merge, the elected stack master would have been the master of one of the merged stacks.

    Note: When stacks partition, the stack master of the original stack will be the master of its partition.

  2. The switch with the highest stack member priority value

    Note: Cisco recommends that you assign the highest priority value to the switch that you prefer to be the stack master. This ensures that the switch is re-elected as stack master if a re-election occurs.

  3. The switch that uses the non-default interface-level configuration
  4. The switch with the higher Hardware/Software priority. These switch software versions are listed from highest to lowest priority:
    1. Cryptographic IP services image software
    2. Noncryptographic IP services image software
    3. Cryptographic IP base image software
    4. Noncryptographic IP base image software

    Note: Switches that run Cryptographic or IP services image will take a longer time to load than Non-Cryptographic or IP base image. When you power on or reset an entire switch stack, some stack members will not participate in the stack master election. This is because stack members that are powered on within the same 20-second time frame participate in the stack master election and have a chance to become the stack master. Stack members that are powered on after the 20-second time frame do not participate in this initial election and only become stack members. At times, switches with lower software priority can become the stack master, but all stack members will participate in the stack master re-election.

  5. The switch with the longest system up-time
  6. The switch with the lowest MAC address

Note: Data forwarding will not be affected within the stack master election.

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