Ubigate iBG2016 Configuration Guide© SAMSUNG Electronics Co., Ltd. 141CHAPTER 8. VRRPIn statically routed networks, when a router fails, all the network devicesconnected to this router are unable to have traffic routed. Typically this meansthese devices cannot reach the Internet or other networks.IPv4’s Virtual Router Redundancy Protocol(VRRP) eliminates this singlepoint of failure by dynamically assigning virtual routers that can providenetwork connectivity in the event the primary router fails. One virtual router isdesignated as the Master which is assigned the IP addresses of connecteddevices. The Master router can manage multiple primary and secondary IPaddresses.Alternate virtual routers(up to 254) are designated as backup virtual routers inthe event the Master fails. Each backup is configured with a priority settingthat determines the order in which backup routers take over in the event theMaster fails. When the Master router fails, the backup router with the smallestpriority number will preempt all other backup routers in assuming the dutiesof the Master router. If you disable the preempt feature(using the no vrrppreempt command), the backup virtual router that is configured as the Mastervirtual router will remain such until the original Master virtual router recovers.The mechanism by which virtual routers in the same network communicatestatus and priority is through VRRP advertisements from the Master virtualrouter. VRRP uses the assigned multicast address 224.0.0.18. By default, theseadvertisements are sent every second, but you can configure the interval.In addition to maintaining network connectivity when a router fails, VRRPallows network administrators to share routing duties with multiple routersthereby reducing the impact of heavy traffic loads.
