Master election
Routers in a VRRP group determine their roles by priority. When a router joins a VRRP group, it has a backup role. The router role changes according to the following situations:
If the backup does not receive any VRRP advertisement when the timer (3 × advertisement interval + Skew_Time) expires, it becomes the master.
If the backup receives a VRRP advertisement with a greater or the same priority within the timer (3 × advertisement interval + Skew_Time), it remains a backup.
If the backup receives a VRRP advertisement with a smaller priority within the timer (3 × advertisement interval + Skew_Time), it remains a backup when operating in non-preemptive mode, or becomes the master when operating in preemptive mode.
The elected master starts a VRRP advertisement interval to periodically send VRRP advertisements to notify the backups that it is operating correctly. Each of the backups starts a timer to wait for advertisements from the master.
After a backup receives a VRRP advertisement, it compares only the priority in the packet with its own priority.
When multiple routers in a VRRP group declare that they are the master because of network problems, the one with the highest priority becomes the master. If two routers have the same priority, the one with the highest IP address becomes the master.