RIPng
Routing Information Protocol - Next Generation (RIPng) is specified for use with IPv6 in RFC 2080. Like the IPv4 version of RIP, this routing protocol is based on a Distance Vector algorithm. RIPng routers compare information for various routes through an IPv6 network, especially the information related to the RIPng metric. Due to the limited number of allowed hops, this protocol is used in small- to moderate-sized networks. The valid metric range is from 1 to 15 (hops). The metric values of 16 and above are defined as `infinity' and are considered unreachable.
An RIPng router is assumed to have interfaces to one or more directly-connected networks. Each router maintains a routing table, with one entry for every reachable destination in the RIPng network. Each routing table entry contains a minimum of:
- IPv6 destination prefix(es)
- total metric cost for the path to the destination(s)
- IPv6 address of the next hop router
- a `route change flag'
- timers
As a UDP-based protocol, the RIPng routing process functions on UDP well-known port number 521 (the `RIPng port'), on which datagrams are sent and received. The RIPng port supports the following:
- Receives all communications received from another router's RIPng process.
- Sends all RIPng routing update messages.
- Unsolicited routing update messages specify this port as the source and destination.
- Responses to request messages are sent to the originating UDP port.
- Specific requests need not come from the RIPng port, but the destination on the targeted device must be the RIPng port.