VRRP supports router redundancy through a prioritized election process
among routers configured as members of the same virtual router (VR).
On a given VLAN, a VR includes two or more member routers configured with
a virtual IP address that is also configured as a real IP address on one of the
routers, plus a virtual router MAC address. The router that owns the IP
address is configured to operate as the Owner of the VR for traffic-forwarding
purposes, and by default has the highest VRRP priority in the VR. The other
router(s) in the VR have a lower priority and are configured to operate as
Backups in case the Owner router becomes unavailable.
The Owner normally operates as the Master for a VR. But if it becomes
unavailable, then a failover to a Backup router belonging to the same VR
occurs, and this Backup becomes the current Master. If the Owner recovers,
a failback occurs, and "Master" status reverts to the Owner. (Note that using
more than one Backup provides additional redundancy, meaning that if both
the Owner and the highest-priority Backup fail, then another, lower-priority
Backup can take over as Master.)
The virtual IP address used by all VRRP routers in a VR instance is a
real IP address that is also configured on the applicable VLAN inter-
face on the VR's Owner router.
The same MAC and virtual IP addresses are included in the VRRP
configuration for the Owner and all Backup routers belonging to the
same VR, and are used as the source addresses for all traffic
forwarded by the VR.
Virtual Router Redundancy Protocol (VRRP)