VRRP overview

In many networks, edge devices are often configured to send packets to a statically configured default router. If this router becomes unavailable, the devices that use it as their first-hop router become isolated from the network. Virtual Router Redundancy Protocol (VRRP) uses dynamic failover to ensure the availability of an end node's default router. This is done by assigning the IP address used as the default route to a "virtual router" or VR. The VR includes:
  • An owner router assigned to forward traffic designated for the virtual router (If the owner is forwarding traffic for the VR, it is the master router for that VR.)

  • One or more prioritized backup routers (If a backup is forwarding traffic for the VR, it has replaced the owner as the master router for that VR.)

This redundancy provides a backup for gateway IP addresses (first-hop routers) so that if a VR's master router becomes unavailable, the traffic it supports will be transferred to a backup router without major delays or operator intervention. This operation can eliminate single-point-of-failure problems and provide dynamic failover (and failback) support. As long as one physical router in a VR configuration is available, the IP addresses assigned to the VR are always available, and the edge devices can send packets to these IP addresses without interruption.

Advantages to using VRRP include:
  • Minimizing failover time and bandwidth overhead if a primary router becomes unavailable.

  • Minimizing service disruptions during a failover.

  • Providing backup for a load-balanced routing solution.

  • Addressing failover problems at the router level instead of on the network edge.

  • Avoiding the need to make configuration changes in the end nodes if a gateway router fails.

  • Eliminating the need for router discovery protocols to support failover operation.

Both VRRPv2 and VRRPv3 are supported. IPv4 VRs can be configured for both version 2 and version 3. IPv6 VRs can only be configured for version 3.

For more information, see General operation.