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Stack Master/Standby Switchover
Many factors may cause master/standby switchovers in a stack. This section describes the master/standby switchovers triggered by MPU failures or commands.
Master/Standby Switchover Triggered by an MPU Failure
Roles in a stack may change if an MPU in the stack fails.
The system master MPU fails.
Figure 1-23 shows the changes of roles in a stack after the system master MPU fails.
- The original standby switch becomes the master switch, and the original system standby MPU becomes the system master MPU.
- The original master switch becomes the standby switch.
- The standby MPU of the original master switch becomes the system standby MPU and synchronizes data with the system master MPU.
The system standby MPU fails.
Figure 1-24 shows the changes of roles in a stack after the system standby MPU fails.
- The master and standby switches retain their roles.
- The standby MPU of the standby switch becomes the system standby MPU and synchronizes data with the system master MPU.
A system candidate standby MPU fails.
Failures of candidate standby MPUs do not cause any change of roles in the stack.
Master/Standby Switchover Triggered by Commands
Figure 1-25 shows the changes of roles in a stack after a master/standby switchover is triggered by a command.
- The original standby switch becomes the master switch, and the original system standby MPU becomes the system master MPU.
- The original system master MPU becomes a candidate system standby MPU, and the original master switch becomes the standby switch.
- The standby MPU of the original master switch becomes the system standby MPU and synchronizes data with the system master MPU.