Virtual Router Redundancy Protocol (VRRP)

Virtual Router Redundancy Protocol (VRRP)
The Virtual Router Redundancy Protocol (VRRP) is designed to eliminate the single point of failure inherent in the static default routed environment by automatically providing alternate router paths. As specified by RFC 2338, VRRP uses an election protocol that dynamically assigns responsibility for a virtual router to one of the VRRP routers on a LAN. The VRRP router controlling the IP address(es) associated with a virtual router is called the Master, and forwards packets sent to these IP addresses.

The election process provides dynamic failover of the forwarding responsibility should the Master become unavailable. The Virtual Router associated with a given alternate path supported by VRRP uses the same IP address and MAC address as the routers for other paths. As a result, the host's gateway information does not change, no matter what path is used. Because of this, VRRP-based redundancy significantly reduces administrative overhead when compared to redundancy schemes that require hosts to be configured with multiple default gateways.

Why VRRP?
With increasingly commoditized products and pricing among service providers, service level agreements and general service availability have assumed a greater role in the marketplace. Once only a domain of the largest Tier 1 providers, many small- and midsize service providers deploy Internet traffic control devices such as routers and switches in redundant configurations.

In today’s service provider market, customers hold providers to a high standard. It is not uncommon to find IP data and telephony services with reliability figures over 99.999%. In a highly-competitive environment, device and link failures are unacceptable. Repeated surveys show that when choosing a service provider, customers value "availability" over every other criteria. "Network reliability" has ranked #1 in each of the last 5 years of eWeek's annual ISP surveys, and “Network performance” has ranked in the top 3. In the 2001 survey, 95% ranked reliability as extremely or very important,
making it by far the leading customer concern.