RIP Overview 975Figure 297 RIP-2 Authentication Message■ Authentication Type: 2 represents plain text authentication, while 3 representsMD5.■ Authentication: Authentication data, including password information whenplain text authentication is adopted or including key ID, MD5 authenticationdata length and sequence number when MD5 authentication is adopted.n ■ RFC 1723 only defines plain text authentication. For information about MD5authentication, refer to RFC2082 “RIP-2 MD5 Authentication”.■ With RIPv1, you can configure the authentication mode in interface view.However, the configuration will not take effect because RIPv1 does not supportauthentication.TRIP Triggered RIP (TRIP), a RIP extension on WAN, is mainly used in dial-up network.Working mechanismRouting information is sent in triggered updates rather than periodic broadcasts toreduce the routing management cost the WAN.■ Only when data in the routing table changes or the next hop is unreachable, arouting update message is sent.■ Since the periodic update delivery is canceled, an acknowledgement andretransmission mechanism is required to guarantee successful updatestransmission on WAN.Message typesRIP use three new types of message which are identified by the value of theCommand filed.■ Update Request (type value 9): Requests needed routes from the peer.■ Update Response (type value 10): Contains the routes requested by the peer.■ Update Acknowledge (type value 11): Acknowledges received UpdateResponse messages.TRIP retransmission mechanism■ If receiving no Update Responses after sending an Update Request, a routersends the request again after a specified interval. If still receiving no UpdateResponse after the upper limit for sending requests is reached, the routerconsiders the neighbor unreachable.■ If receiving no Update Acknowledge after sending an Update Response, arouter sends the Update Response again after a specified interval. If stillCommand0xFFFFAuthentication (16 octets)Version UnusedAuthentication type0 7 15 31
