1-2Each RIPng router maintains a routing database, including route entries of all reachable destinations. Aroute entry contains the following information:z Destination address: IPv6 address of a host or a network.z Next hop address: IPv6 address of a neighbor along the path to the destination.z Egress interface: Outbound interface that forwards IPv6 packets.z Metric: Cost from the local router to the destination.z Route time: Time that elapsed since a route entry is last changed. Each time a route entry ismodified, the routing time is set to 0.z Route tag: Identifies the route, used in a routing policy to control routing information. Forinformation about routing policy, refer to Routing Policy Configuration in the IP Routing Volume.RIPng Packet FormatBasic formatA RIPng packet consists of a header and multiple route table entries (RTEs). The maximum number ofRTEs in a packet depends on the IPv6 MTU of the sending interface.Figure 1-1 shows the packet format of RIPng.Figure 1-1 RIPng basic packet format…z Command: Type of message. 0x01 indicates Request, 0x02 indicates Response.z Version: Version of RIPng. It can only be 0x01 currently.z RTE: Route table entry, 20 bytes for each entry.RTE formatThere are two types of RTEs in RIPng.z Next hop RTE: Defines the IPv6 address of a next hopz IPv6 prefix RTE: Describes the destination IPv6 address, route tag, prefix length and metric in theRIPng routing table.Figure 1-2 shows the format of the next hop RTE:Figure 1-2 Next hop RTE formatIPv6 next hop address is the IPv6 address of the next hop.Figure 1-3 shows the format of the IPv6 prefix RTE.
