VRRP (Virtual Router Redundancy Protocol, referred to as VRRP), is an IP protocol suite, we know the IP protocol suite, which has a ICMP, OSPF, VRRP also IP protocol suite, protocol number 112. In VRRP, the apparatus has two roles (Master, Backup), in which the Master is responsible for running the business flow, while Backup responsible for backing up, hang up when the Master, Backup automatically preempt Master, then go all the data from the Master. VRRP is mainly used for redundant backup exit link, you can have more than one backup gateway device to join the group, but only one Master device, hang up when the Master device, other devices automatically preempt Master Backup Device reliability of safety nets.
There are three VRRP state machine, init, backup, master, master when the election time, each device to send its own priority to the adjacent device, when the other device is received over the priority is greater than he is, Backup automatically becomes the Master, when the election is completed, Backup devices within a certain period of time have not received the Master range of equipment sent by priority information, it becomes a Backup Master device. VRRP priority election by Master of priority, is represented by 0 0--254 not participate in the elections, is 254, expressed as a Master, when the priority is the same, relatively IP address, ip address large as Master. VRRP has a checking mechanism, when the line Master of broken equipment, checking mechanism to query took off after the line is automatically reduced to the lower priority than the highest priority Backup, so you can prevent because after Master device hang, traffic Master device is lost.
Fixed VRRP multicast addresses to use for 224.0.0.18, we know ospf multicast address used for the 224.0.0.5,6 (DR, BDR sent to the DD DROTHER, LSA Request or LSA Update the target address is AllSPFRouter224.0.0.5, ,, 224.0.0.6 on the contrary), and rip multicast address used is 224.0.0.9.
In business, most of the internal network are divided into a number of vlan, many people will think of these vlanif VRRP Master of the device is the same device, another device to do a backup, do not run data. In fact not the case, experienced engineers will make these devices work together, that is, choose one of the devices as part of the Master VRRP vlan, and other equipment as the rest of the vlan of the VRRP Master. Doing so will not allow a device in which the load is high, while the other devices but the idle state.
Ado, let's do an experiment it!
In eNSP, we take a vlan2 to experiment, create vrrp on vlanif interface. sw1, sw2, sw3, Create sw4 Vlan2, adding good interface information, SW1 and SW2 E / 0/1, E0 / 0/2 interface TRUNK, by allowing VLAN2, SW3 and SW4 of E0 / 0/1, E0 / 0/2 interface TRUNK interface to allow through vlan2, E0 / 0/3 interface access interface default vlan 2. SW1 wherein the interface vlan ip address as 192.168.1.1 24, SW2 of the interface vlan 2de ipdiz wei 192.168.1.2 24. virtual-ip is 192.168.1.254.