1-3
Figure 1-3
IPv6 prefix RTE format
IPv6 prefix (16 octets)
Route tag
Prefix length
Metric
0
7
15
31
z
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 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:
z
A response to a request
z
An update periodically
z
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 and whether the port
number is correct. The response packet that failed the check will be discarded.
Protocols and Standards
z
RFC 2080: RIPng for IPv6
z
RFC 2081: RIPng Protocol Applicability Statement
Configuring RIPng Basic Functions
This 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 related
interface configurations, such as assigning an IPv6 address.
Configuration Prerequisites
Before the configuration, accomplish the following tasks first:
z
Enable IPv6 packet forwarding.
