26.1.1 Overview

(1) Message Type

RIPng uses two types of messages: request messages and response messages. A response message is used to reply to a request from another router. Response messages are also used to notify other routers of Switch's routing information, either periodically or when there is a change in the network topology.

(2) Operation processing

At startup, the Switch sends all of its request messages to neighboring routers, and requests neighboring routers to send all of their routing information. After startup, the Switch sends responses for the following purposes:

• To send relevant routing information in response to a request from a neighboring router

• To periodically report routing information. At 30-second intervals the Switch sends all of its routing information as responses to neighboring routers.

• To report a detected route change. The Switch sends routing information regarding a changed route as a response to neighboring routers.

On receipt of a response from a neighboring router, the Switch updates its routing information if a route change has been detected. Responses are also used to check the transmission status to a neighboring router. If no response is received for 180 seconds or longer, the neighboring router is deemed unreachable and the routing table is updated with an alternate route, if available. Otherwise, the unreachable route is deleted.

(3) Suppressing Routing Loops

The Switch use split horizon logic to prevent loops in forwarding routes. Split horizon processing stops received information from being forwarded to the interface from which the information originated.

(4) Functional difference between RIPng(IPv6) and RIP(IPv4)

The following table describes the functional differences between RIPng (IPv6) and RIP (IPv4).