The Virtual Router Redundancy Protocol (VRRP) eliminates the single point of failure inherent in the static default-routed environment. VRRP describes a method of implementing a redundant IP interface that provides dynamic failover if the VRRP master router (MR) becomes unavailable.
VRRP provides information about the state of a router. However, PIM operates independently of VRRP group states. The PIM DR and the VRRP MR may not be the same router and IP multicast traffic may not necessarily follow the same path as elected by VRRP.
To leverage the redundancy capabilities of VRRP that are lacking in PIM, the VRRP Aware PIM mechanism allows PIM to monitor and react to changes in the VRRP MR. This ensures that the multicast traffic follows the unicast traffic through the same gateway as the VRRP MR, providing consistent IP multicast forwarding in a redundant network.