RIP

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When RIP routers advertise updates, they tell the pre-calculate the metric for that router by adding 1 to the routes current metric. If multiple equal cost paths exist, RIP will install up to 4 of these routes into the routing table. This can be changed to 6 with the //**#ip maximum-paths**// command.

=Convergence and Loop Prevention=



In RIP, the network command can only take a classful network as an argument. You can disable by by issuing the //**#no auto-summary**// command from within the RIP configuration. Since RIP cannot be enabled per interface, you may enable RIP for an undesired interface. There are a few ways to disable the sending and receiving of RIP information.



If you have an interface to which multiple hosts are connected and you only want to advertise to a specific host, you can use the **passive-interface** command followed by the **neighbor** command, which is force RIP to send only unicast updates.

=Authentication=

RIP, like other routing protocols, uses keys. These keys can be group into a keychain and associated with the RIP configuration via //**#ip authentication key-chain **//. The method of authentication can be configured with //**#ip rip authentication mode {text|md5}**//. The default is text.

The following is an example of a key chain configuration: code code
 * 1) key chain test
 * 2) key 1
 * 3) key-string fred
 * 4) accept-lifetime
 * 5) send-lifetime
 * 6) key 2
 * 7) key-string wilma
 * 8) accept-lifetime
 * 9) send-lifetime

=Next-hop and Split Horizon=

Split horizon can be configured per interface with the //**#ip split-horizon**// command. RIP can also change the next-hop of routes when advertising them out.

=Offset Lists=

Offset lists allow RIP to add to a routes metric before advertising it out. Offset lists match based on an access list and are configured with the command //**#offset list   .**// The offset is added to that of the original metric. = = =Route Filtering=

Routes can be filtered inbound, outbound or for the entire RIP process. To filter with a distribute list, the #distribute-list command is used under the RIP configuration, with an associated ACL. Any routes matching the permit clause are allowed and deny routes are rejected.

//**#distrbute-list  **//

A prefix list can also be used in place of an ACL.

//**#distribute-list prefix  **//