VRRP operation

VRRP supports router redundancy through a prioritized election process among routers configured as members of the same virtual router (VR).

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

  • 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. By default, this router has the highest VRRP priority in the VR. Any other routers in the VR have a lower priority and are configured to operate as Backups if the Owner router becomes unavailable.
The Owner normally operates as the Master for a VR. If the Owner becomes unavailable, a failover to a Backup router belonging to the same VR occurs. This Backup becomes the Master. If the Owner recovers, a failback occurs, and Master status reverts to the Owner.
NOTE:

Using more than one Backup provides additional redundancy. If the Owner and the highest-priority Backup fail, another lower-priority Backup can take over as Master.

The image shown here depicts a basic VLAN topology. In this example, Routers 1, 2 and 3 form a VRRP group. The IP address of the group is the same address configured for the SVI interface of R1 (10.10.100.1).

Because the virtual IP address uses the IP address of the SVI interface of Router R1, Router R1 is the master (also known as IP address Owner).
  • As the master, R1 owns the virtual IP address of the VRRP group and forwards packets sent to this IP address.

  • Clients 1 through 3 are configured with the default gateway IP address of 10.10.100.1.

  • Routers R2 and R3 function as backups. If the master fails, the backup router with highest priority becomes the master and takes over the virtual IP address to provide uninterrupted service for the clients connected to L2 Switch. When Router R1 recovers, it becomes master again.