612 G8264 Application Guide for ENOS 8.4VRRP OverviewIn a high‐availability network topology, no device can create a singlepoint‐of‐failure for the network or force a single point‐of‐failure to any other partof the network. This means that your network will remain in service despite thefailure of any single device. To achieve this usually requires redundancy for allvital network components.VRRP enables redundant router configurations within a LAN, providing alternaterouter paths for a host to eliminate single points‐of‐failure within a network. Eachparticipating VRRP‐capable routing device is configured with the same virtualrouter IPv4 address and ID number. One of the virtual routers is elected as themaster, based on a number of priority criteria, and assumes control of the sharedvirtual router IPv4 address. If the master fails, one of the backup virtual routerswill take control of the virtual router IPv4 address and actively process trafficaddressed to it.With VRRP, Virtual Interface Routers (VIR) allow two VRRP routers to share an IPinterface across the routers. VIRs provide a single Destination IPv4 (DIP) addressfor upstream routers to reach various servers, and provide a virtual defaultGateway for the servers.VRRP ComponentsEach physical router running VRRP is known as a VRRP router.Virtual RouterTwo or more VRRP routers can be configured to form a virtual router (RFC 2338).Each VRRP router may participate in one or more virtual routers. Each virtualrouter consists of a user‐configured virtual router identifier (VRID) and an IPv4address.Virtual Router MAC AddressThe VRID is used to build the virtual router MAC Address. The five highest‐orderoctets of the virtual router MAC Address are the standard MAC prefix(00‐00‐5E‐00‐01) defined in RFC 2338. The VRID is used to form the lowest‐orderoctet.Owners and RentersOnly one of the VRRP routers in a virtual router may be configured as the IPv4address owner. This router has the virtual router’s IPv4 address as its real interfaceaddress. This router responds to packets addressed to the virtual router’s IPv4address for ICMP pings, TCP connections, and so on.There is no requirement for any VRRP router to be the IPv4 address owner. MostVRRP installations choose not to implement an IPv4 address owner. For thepurposes of this chapter, VRRP routers that are not the IPv4 address owner arecalled renters.
