Configuring Layer 3 Redundancy with Virtual Router Redundancy Protocol – VRRP and Gateway Load Balancing Protocol – GLBP
What is VRRP?

Like HSRP, Virtual Router Redundancy Protocol (VRRP) allows a group of routers to form a single virtual router. The LAN workstations are then configured with the address of the virtual router as their default gateway. VRRP differs from HSRP in the following ways:

  • VRRP is an IEEE standard for router redundancy, HSRP is a Cisco proprietary
  • The virtual router, representing a group of routers, is known as a VRRP group.
  • The active router is referred to as the master virtual router.
  • The master virtual router may have the same IP address of the virtual router group.
  • Multiple routers can function as backup routers.

In the example, routers A, B, and C are members of a VRRP group. The IP address of the virtual router is the same as that of the LAN interface of router A (10.0.0.1). Router A is responsible for forwarding packets sent to this IP address.

The clients have a gateway address of 10.0.0.1. Routers B and C are backup routers. If the master router fails, the backup router with the highest priority becomes the master router. When router A recovers, it resumes the role of master router.

VRRP offers these redundancy features:

  • VRRP provides redundancy for the real IP address of a router, or for a virtual IP address shared among the VRRP group members.
  • If a real IP address is used, the owning router becomes the master. If a virtual IP address is used, the master is the router with the highest priority.
  • A VRRP group has one master router and one or more backup routers. The master router uses VRRP messages to inform group members of the IP addresses of the backup routers.