RIPng working mechanism
RIPng is a routing protocol based on the distance vector (D-V) algorithm. RIPng uses UDP packets to exchange routing information through port 521.
RIPng uses a hop count to measure the distance to a destination. The hop count is the metric or cost. The hop count from a router to a directly connected network is 0. The hop count between two directly connected routers is 1. When the hop count is greater than or equal to 16, the destination network or host is unreachable.
By default, the routing update is sent every 30 seconds. If the router receives no routing updates from a neighbor within 180 seconds, the routes learned from the neighbor are considered unreachable. If no routing update is received within another 240 seconds, the router removes these routes from the routing table.
RIPng supports split horizon and poison reverse to prevent routing loops and route redistribution.
Each RIPng router maintains a routing database, which includes route entries of all reachable 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.
Route time—Time elapsed since a route entry is last changed. Each time a route entry is modified, the routing time is set to 0.
Route tag—Identifies the route used in a routing policy to control routing information. For more information about routing policy, see "Configuring routing policies."