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.