65 IPV6 RIPNG C ONFIGURATIONWhen configuring RIPng, go to these sections for information you are interestedin:■ “Introduction to RIPng” on page 1069■ “Configuring RIPng Basic Functions” on page 1071■ “Configuring RIPng Advanced Functions” on page 1072■ “Optimizing the RIPng Network” on page 1074■ “Displaying and Maintaining RIPng” on page 1076■ “RIPng Configuration Example” on page 1077Introduction 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: IPv6 address in 128-bit.■ 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.
