The Virtual Router Redundancy Protocol (VRRP) for IPv4 is defined in the IETF RFC 3768, Virtual Router Redundancy Protocol. VRRP for IPv6 is specified in draft-ietf-vrrp-unified-spec-02.txt and only applies to the 7750 SR and 7950 XRS. VRRP describes a method of implementing a redundant IP interface shared between two or more routers on a common LAN segment, allowing a group of routers to function as one virtual router. When this IP interface is specified as a default gateway on hosts directly attached to this LAN, the routers sharing the IP interface prevent a single point of failure by limiting access to this gateway address. VRRP can be implemented on IES service interfaces and on core network IP interfaces.
The VRRP standard RFC 3768 uses the term ‟master” state to denote the virtual router that is currently acting as the active forwarding router for the VRRP instance. This guide uses the term "active" as much as possible.
If the virtual router in master state fails, the backup router configured with the highest acceptable priority becomes the active virtual router. The new active router assumes the normal packet forwarding for the local hosts.
Figure: VRRP Configuration shows an example of a VRRP configuration.
