VRRP (Virtual Routing Redundancy Protocol): routing equipment by several coalition of a virtual routing equipment, the ip address of the virtual routing device as the default gateway address for the user to achieve communication with the outside. When the gateway fails, VRRP protocol to quickly elect a new gateway device to assume the data traffic to ensure reliable communication network. Ip using VRRP packets as the transport protocol packets, the protocol number 112, fixed transmitting multicast address 224.0.0.18 through the election protocol packets at a router acts as master, and other devices as Backup, backup gateway to achieve . VRRP advertisement to only use this kind of message.
master election: first compares the priority of each router priority becomes the master large, the same priority, then, is more an interface ip address, ip address large become master. master will periodically send advertisement packets, in fact, is one second sent once every 3 seconds if the backup master did not receive the message sent by the advertisement is considered master down, it will be a new round of elections.