Preempt mode is a true or false configured value which controls whether a specific backup virtual router preempts a lower priority master. The IP address owner will always become master when available. Preempt mode cannot be set to false on the owner virtual router. The default value for preempt mode is true.
When preempt mode is true, the advertised priority from the incoming VRRP advertisement message from the current master is compared to the local configured priority. If the local priority is higher, the received VRRP advertisement message is discarded. This will result in the eventual expiration of the master down timer causing a transition to the master state. If the received priority is equal to the local priority, the message is not discarded and the current master will not be discarded. Note that when in the backup state, the received primary IP address is not part of the decision to preempt and is not used as a tie breaker when the received and local priorities are equal.
When preempt is enabled, the virtual router instance overrides any non-owner master with an in-use message priority value less than the virtual router instance in-use priority value. If preempt is disabled, the virtual router only becomes master if the master down timer expires before a VRRP advertisement message is received from another virtual router.