VRRP Master Preemption

VRRP master preemption is a feature that allows a VRRP backup router with a higher VRRP priority to take control from a lower priority backup that is acting as the master.

VRRP election occurs as described in ESRP Master Election. VRRP preemption occurs when a VRRP backup router is added to the network or recovers, and that backup router has a higher priority than the current backup VRRP that is operating as the master.

Note

The VRRP router IP address owner always preempts, independent of the VRRP preemption setting.

When a VRRP backup router preempts the master, it does so in one of the following ways:

If the preempt delay timer is configured for between 1 and 3600 seconds and the lower-priority master is still operating, the router preempts the master when the timer expires.
If the preempt delay timer is configured for 0, the router preempts the master after three times length of the hello interval.
If the higher priority router stops receiving advertisements from the current master for three times the length of the hello interval, it takes over mastership immediately.

The preempt delay timer provides time for a recovering router to complete start up before preempting a lower-priority router. If the preempt delay timer is configured too low, traffic is lost between the time the preempting router takes control and the time when it has completed startup.