• Homogeneous stack
  • Mixed stack
    • mixed hadrware
    • mixed software
    • mixed hard and soft

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 stack master. Every stack member is identified by its own stack member number .
The system-level features supported on the stack master are supported on the entire switch stack.

Master election:

  1. current master
  2. highest stack member priority value (1-15; def 15)
  3. switch that is not using the default interface-level configuration
  4. switch with the higher priority feature set and software image combination
    1. IP services crypto
    2. IP services non crtypto
    3. IP base crypto
    4. IP Base non crypto
  5. Longest up-time.
  6. lowest MAC

A stack master retains its role unless one of these events occurs:

  • The switch stack is reset. 
  • The stack master is removed from the switch stack.
  • The stack master is reset or powered off.
  • The stack master fails.
  • The switch stack membership is increased by adding powered-on standalone switches or switch stacks.

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 become stack members. All stack members participate in re-elections.

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