3Com Switch 8800 Advanced Software V5 Configuration Guide

290 CHAPTER 29: IPV6 RIPNG CONFIGURATION

RIPng supports Split Horizon and Poison Reverse to prevent routing loops, and

route redistribution.

Each RIPng router maintains a routing database, including 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 that 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 routing policy to control routing

information.

RIPng Packet Format Basic format

A RIPng packet consists of a header and multiple Route Table Entries (RTEs). The

maximum number of RTEs in a packet depends on the MTU of the sending

interface.

Figure 79 shows the packet format of RIPng.

Figure 79 RIPng basic packet format

■ Command: Type of message. 0x01 indicates Request, 0x02 indicates Response.

■ Version: Version of RIPng. It can only be 0x01 currently.

■ RTE: Route table entry, 20 bytes for each entry.

RTE format

There are two types of RTE in RIPng.

■ Next hop RTE: Defines the IPv6 address of a next hop

■ IPv6 prefix RTE: Describes the destination IPv6 address, route tag, prefix length

and metric in the RIPng routing table.

Figure 80 shows the format of the next hop RTE:

Command

Route table entry 1 (20 octets)

Version Must be zero

Route table entry n (20 octets)

0 7 15 31