33 IPV6 RIPNG C ONFIGURATIONn ■ The term “router” in this document refers to a Layer 3 switch running routingprotocols.■ The Switch 4800G only support single RIPng process.Introduction to RIPng RIP next generation (RIPng) is an extension of RIP-2 for IPv4. Most RIP concepts areapplicable in RIPng.RIPng for IPv6 made the following changes to RIP:■ UDP port number: RIPng uses UDP port 521 for sending and receiving routinginformation.■ Multicast address: RIPng uses FF02:9 as the link-local multicast address.■ Destination Prefix: 128-bit destination address prefix.■ Next hop: 128-bit IPv6 address.■ Source address: RIPng uses FE80::/10 as the link-local source addressRIPng WorkingMechanismRIPng is a routing protocol based on the distance vector (D-V) algorithm. RIPnguses UDP packets to exchange routing information through port 521.RIPng uses a hop count to measure the distance to a destination. The hop count isreferred to as metric or cost. The hop count from a router to a directly connectednetwork is 0. The hop count between two directly connected routers is 1. Whenthe hop count is greater than or equal to 16, the destination network or host isunreachable.By default, the routing update is sent every 30 seconds. If the router receives norouting updates from a neighbor after 180 seconds, the routes learned from theneighbor are considered as unreachable. After another 240 seconds, if no routingupdate is received, the router will remove these routes from the routing table.RIPng supports Split Horizon and Poison Reverse to prevent routing loops, androute redistribution.Each RIPng router maintains a routing database, including route entries of allreachable destinations. A route entry contains the following information:■ Destination address: IPv6 address of a host or a network.■ Next hop address: IPv6 address of a neighbor along the path to the destination.■ Egress interface: Outbound interface that forwards IPv6 packets.■ Metric: Cost from the local router to the destination.
