HP VPN Firewall Appliances Appendix Protocol Reference

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• Prefix length—Length of the IPv6 address prefix
• Metric—Cost of a route
RIPng packet processing procedure
Request packet
When a RIPng router first starts or must update entries in its routing table, it usually sends a multicast
request packet to ask for needed routes from neighbors.
The receiving RIPng router processes RTEs in the request. If only one RTE exists with the IPv6 prefix and
prefix length both being 0 and with a metric value of 16, the RIPng router responds with the entire routing
table information in response messages. If multiple RTEs exist in the request message, the RIPng router
examines 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 follows:
• 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 and whether the port
number is correct. The response packet that failed the check is discarded.
Protocols and standards
• RFC 2080, RIPng for IPv6
• RFC 2081, RIPng Protocol Applicability Statement