3Com Switch 8800 Advanced Software V5 Configuration Guide

Introduction to RIPng 291
Figure 80 Next hop RTE format
IPv6 next hop address is the IPv6 address of the next hop.
Figure 81 shows the format of the IPv6 prefix RTE.
Figure 81 IPv6 prefix RTE format
■ IPv6 prefix: Destination IPv6 address prefix.
■ Route tag: Route tag.
■ Prefix len: Length of the IPv6 address prefix.
■ Metric: Cost of a route.
RIPng Packet Processing
Procedure
Request packet
When a RIPng router first starts or needs to update some entries in its routing
table, generally a multicast 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 prefix and prefix length both being 0, and with a metric value of 16,
the RIPng router will respond with the entire routing table information in response
messages. If there are multiple RTEs in the request message, the RIPng router will
examine each RTE, update its metric, and send the requested routing information
to the requesting router in the response packet.
Response packet
The response packet containing the local routing table information is generated
as:
■ A response to a request
■ An update periodically
■ A trigged update caused by route change
After receiving a response, a router checks the validity of the response before
adding the route to its routing table, such as whether the source IPv6 address is
the link-local address, whether the port number is correct. The response packet
failed the check will be discarded.
Protocols and Standards ■ RFC2080: RIPng for IPv6
IPv6 next hop address (16 octets)
Must be zero Must be zero 0xFF
0715 31
IPv6 prefix (16 octets)
Route tag Prefix length Metric
0 7 15 31