Preempt mode is a true or false configured value that controls whether a specific backup virtual router preempts a lower-priority master. The IP address owner always becomes master when available. Preempt mode cannot be set to false on the owner virtual router. The default value for preempt mode is true.
When the preempt mode is true, a master non-owner virtual router only allows itself to be preempted when the incoming VRRP advertisement message priority field value is one of the following:
Greater than the virtual router in-use priority value
Equal to the in-use priority value, and the source IP address (primary IP address) is greater than the virtual router instance primary IP address
A backup router only attempts to become the master router if the preempt mode is true and the received VRRP advertisement priority field is less than the virtual router in-use priority value.