54Virtual Router Redundancy Protocol(VRRP)Virtual router redundancy protocol (VRRP) is supported on the Z9000 platform.VRRP OverviewVRRP is designed to eliminate a single point of failure in a statically routed network.VRRP specifies a MASTER router that owns the next hop IP and MAC address for end stations on a localarea network (LAN). The MASTER router is chosen from the virtual routers by an election process andforwards packets sent to the next hop IP address. If the MASTER router fails, VRRP begins the electionprocess to choose a new MASTER router and that new MASTER continues routing traffic.VRRP uses the virtual router identifier (VRID) to identify each virtual router configured. The IP address ofthe MASTER router is used as the next hop address for all end stations on the LAN. The other routers theIP addresses represent are BACKUP routers.VRRP packets are transmitted with the virtual router MAC address as the source MAC address. The MACaddress is in the following format: 00-00-5E-00-01-{VRID}. The first three octets are unchangeable. Thenext two octets (00-01) indicate the address block assigned to the VRRP protocol, and are unchangeable.The final octet changes depending on the VRRP virtual router identifier and allows for up to 255 VRRProuters on a network.The following example shows a typical network configuration using VRRP. Instead of configuring thehosts on the network 10.10.10.0 with the IP address of either Router A or Router B as their default router;their default router is the IP address configured on the virtual router. When any host on the LAN segmentwants to access the Internet, it sends packets to the IP address of the virtual router.In the following example, Router A is configured as the MASTER router. It is configured with the IPaddress of the virtual router and sends any packets addressed to the virtual router through interfaceGigabitEthernet 1/1 to the Internet. As the BACKUP router, Router B is also configured with the IP addressof the virtual router. If, for any reason, Router A becomes unavailable, VRRP elects a new MASTER Router.Router B assumes the duties of Router A and becomes the MASTER router. At that time, Router Bresponds to the packets sent to the virtual IP address.All workstations continue to use the IP address of the virtual router to address packets destined to theInternet. Router B receives and forwards them on interface GigabitEthernet 10/1. Until Router A resumesoperation, VRRP allows Router B to provide uninterrupted service to the users on the LAN segmentaccessing the Internet.For more detailed information about VRRP, refer to RFC 2338, Virtual Router Redundancy Protocol.Virtual Router Redundancy Protocol (VRRP) 875
