Nokia Network Voyager for IPSO 4.0 Reference Guide 1834 Virtual Router Redundancy Protocol(VRRP)This chapter describes the Nokia IPSO implementation of VRRP and how to configure it onyour system.VRRP OverviewVirtual Router Redundancy Protocol (VRRP) provides dynamic failover of IP addresses fromone router to another in the event of failure. VRRP is defined in RFC 3768. The Nokiaimplementation of VRRP includes all of the features described in RFC 3768, plus the additionalfeature of monitored circuit, described below.Nokia supports VRRP for IPv6. For more information about the Nokia implementation and howto configure VRRP for IPv6 interfaces, see “Configuring VRRP for IPv6.”VRRP allows you to provide alternate router paths for end hosts that are configured with staticdefault routes. Using static default routes minimizes configuration and processing overhead onend hosts. When end hosts are configured with static routes, normally the failure of the masterrouter results in a catastrophic event, isolating all hosts that are unable to detect availablealternate paths to their gateway. You can implement VRRP to provide a higher availabilitydefault path to the gateway without needing to configure dynamic routing or router discoveryprotocols on every end host.How VRRP WorksVRRP uses a virtual router to allow end hosts to use an IP address that is part of the virtual routeras the default first-hop router. A virtual router is defined as a unique virtual router ID (VRID)and the router IP addresses of the default route on a LAN, and is comprised of a master routerand at least one backup router. If the master platform fails, VRRP specifies an election protocolthat dynamically assigns responsibility to a backup platform for forwarding IP traffic sent to theIP address of the virtual router.A virtual router, or VRID, consists of a master platform and one or more backups. The mastersends periodic VRRP advertisements (also known as hello messages). To minimize networktraffic, backups do not send VRRP advertisements.
