1-2Configuring a default route for network hosts facilitates your configuration, but also requires highperformance stability of the device acting as the gateway. Using more egress gateways is a commonway to improve system reliability, introducing the problem of routing among the multiple egresses.Virtual Router Redundancy Protocol (VRRP) is designed to address this problem. VRRP adds a groupof routers that can act as network gateways to a VRRP group, which forms a virtual router. Routers inthe VRRP group elect a master through the VRRP election mechanism to take the responsibility of agateway, and hosts on a LAN only need to configure the virtual router as their default network gateway.VRRP is an error-tolerant protocol, which improves the network reliability and simplifies configurationson hosts. Deploying VRRP on multicast and broadcast LANs such as Ethernet, you can ensure that thesystem can still provide highly reliable default links without changing configurations (such as dynamicrouting protocols, route discovery protocols) when a router fails, and prevent network interruption due tofailure of a single link.VRRP works in one of the following two modes:z Standard protocol mode: Includes two versions based on RFCs: VRRPv2 and VRRPv3. VRRPv2is based on IPv4, and VRRPv3 is based on IPv6. The two versions implement the same functionsbut are applied in different network environments. Refer to VRRP Standard Protocol Mode fordetails.z Load balancing mode: Extends the standard protocol mode and realizes load balancing. Refer toVRRP Load Balancing Mode for details.VRRP Standard Protocol ModeIntroduction to VRRP GroupVRRP combines a group of routers (including a master and multiple backups) on a LAN into a virtualrouter called VRRP group.A VRRP group has the following features:z A virtual router has a virtual IP address. A host on the LAN only needs to know the IP address of thevirtual router and uses the IP address as the next hop of the default route.z Every host on the LAN communicates with external networks through the virtual router.z Routers in the VRRP group elect the master acting as the gateway according to their priorities. Theother routers function as the backups. When the master fails, to ensure that the hosts in thenetwork segment can communicate with the external networks uninterruptedly, the backups in theVRRP group elect a new gateway to undertake the responsibility of the failed master.
