Standby Controller Election

Candidates for standby controller must meet the following criteria:

  • The unit is operational, and the image and module configuration match those of the active controller.
  • The runtime configuration matches that of the active controller.

If more than one unit in the stack meets these criteria, the standby controller is chosen according to the following criteria, in the order shown:

  • Priority - The unit with the highest priority value.
  • Current standby - The unit that is currently the standby controller.
  • Bootup master - The unit that was the active controller before the stack was reloaded.
  • Bootup standby - The unit that was the standby controller before the stack was reloaded.

Once the standby controller is identified, the following internal events take place.

  1. The standby controller is assigned by the active controller 30 to 60 seconds after election (60 seconds if the active controller boots up in less than 120 seconds).
  2. The standby controller receives and processes the runtime configuration sent by the active controller.
  3. The standby controller learns the protocols within 70 seconds.

    When the standby controller is fully synchronized, the system is ready for a switchover or failover.

Parent topic: Standby Controller Role in Hitless Stacking