Election of the master router
VRRP dynamically elects the router that is to be the master. In most cases, the master router is simply the router with the interface that has the highest configured priority. If two interfaces have identical priorities, the router with the interface that has the higher IP address is elected master.
If the master interface fails, the interface with the next-highest priority is elected master and assumes the virtual address of the group. If the system is configured to comply with RFC 3768 and RFC 5798, the network continues to use the well-defined MAC address to locate the device that is using the VIP. The new master also ensures that all network devices are notified of the change by sending a gratuitous ARP message.
The priority of the master interface is typically set to 50 greater than the other routers in the set. The backup interface can be left with the default priority; however, if more than one interface is acting as a backup, they could be configured with different priorities.
The purpose of the modifications to the VRRP state and priority is to adjust which router is the VRRP Master. Care should be taken so that initial priorities across routers are within the adjustment range. If Router A has a base priority of 200 and an adjustment of 10 while Router B has a priority of 150 and an adjustment of 10, then Router A will become master with an effective priority of 210 when it's tracked monitor/path pair is compliant. If Router A's tracked monitor/path becomes noncompliant then it will remain as master, as it's base priority is higher than Router B's effective priority