Once RIP is up and running, it can largely be left alone. However, there are a number of commands that you should be familiar with in order to gain information about the status of RIP, or for troubleshooting purposes.
Of these commands, the most basic and useful is the show ip protocols command. The command will provide you with information about the interfaces on which RIP is configured, the sources of routing information, and the timer values configured.
RouterA#sh ip protocols
Routing Protocol is "rip"
Sending updates every 30 seconds, next due in 26 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Outgoing update filter list for all interfaces is
Incoming update filter list for all interfaces is
Redistributing: rip
Default version control: send version 1, receive any version
Interface Send Recv Key-chain
Ethernet0 1 1 2
Serial0 1 1 2
Routing for Networks:
10.0.0.0
Routing Information Sources:
Gateway Distance Last Update
10.0.20.2 120 00:00:19
Distance: (default is 120)
Notice that this router is receiving updates from address 10.0.20.2, the near interface on Router B.
In order to gain more information about the actual contents of the RIP traffic moving between systems, use the debug ip rip command. This particular command is like a toggle switch – debugging information that shows the contents of RIP updates sent and received will continue to appear on-screen until you turn it off with the no debug ip rip command.
RouterA#debug ip rip
RIP protocol debugging is on
22:48:34: RIP: received v1 update from 10.0.20.2 on Serial0
22:48:34: 10.0.30.0 in 1 hops
22:48:38: RIP: sending v1 update to 255.255.255.255 via Ethernet0 (10.0.10.1)
22:48:38: subnet 10.0.20.0, metric 1
22:48:38: RIP: sending v1 update to 255.255.255.255 via Serial0 (10.0.20.1)
22:48:38: subnet 10.0.20.0, metric 1
RouterA#no debug ip rip
Note that the debug ip rip command shows the RIP updates both sent and received on a particular interface, along with associated subnet and metric information. Remember than a metric of 16 suggests an unreachable network in RIP.
Although you don’t need to know how to do this for the exam, it’s always nice to know how to change the default timers used by a protocol. The command to do so is timers basic, and is issued from the routing protocol configuration level. One important note here – if you do decide to change the timers on one router, you should also change the timers on every router. Otherwise, you’ll be dealing with one very unpredictable network potentially susceptible to routing loops.
RouterA(config)#router rip
RouterA(config-router)#timers basic ?
<0-4294967295> Interval between updates
RouterA(config-router)#timers basic 30 ?
<1-4294967295> Invalid
RouterA(config-router)#timers basic 30 180 ?
<0-4294967295> Holddown
RouterA(config-router)#timers basic 30 180 180 ?
<1-4294967295> Flush
RouterA(config-router)#timers basic 30 180 180 240
I used the help function to walk through the timers basic command step by step to show you the order of the entries – update, invalid, holddown, and flush. Ultimately, the same command can be used to set IGRP timers.
