1-3Figure 1-3 IPv6 prefix RTE formatIPv6 prefix (16 octets)Route tag Prefix length Metric0 7 15 31z IPv6 prefix: Destination IPv6 address prefix.z Route tag: Route tag.z Prefix len: Length of the IPv6 address prefix.z Metric: Cost of a route.RIPng Packet Processing ProcedureRequest packetWhen a RIPng router first starts or needs to update some entries in its routing table, generally amulticast request packet is sent to ask for needed routes from neighbors.The receiving RIPng router processes RTEs in the request. If there is only one RTE with the IPv6 prefixand prefix length both being 0, and with a metric value of 16, the RIPng router will respond with theentire routing table information in response messages. If there are multiple RTEs in the requestmessage, the RIPng router will examine each RTE, update its metric, and send the requested routinginformation to the requesting router in the response packet.Response packetThe response packet containing the local routing table information is generated as:z A response to a requestz An update periodicallyz A trigged update caused by route changeAfter receiving a response, a router checks the validity of the response before adding the route to itsrouting table, such as whether the source IPv6 address is the link-local address and whether the portnumber is correct. The response packet that failed the check will be discarded.Protocols and Standardsz RFC 2080: RIPng for IPv6z RFC 2081: RIPng Protocol Applicability StatementConfiguring RIPng Basic FunctionsThis section presents the information to configure the basic RIPng features.You need to enable RIPng first before configuring other tasks, but it is not necessary for RIPng relatedinterface configurations, such as assigning an IPv6 address.Configuration PrerequisitesBefore the configuration, accomplish the following tasks first:z Enable IPv6 packet forwarding.
