RIP and IGRP

geezer

Hi

Working my way through the Todd Lammle Certified Network Associate Study Guide: Exam 640-801, 5th Edition book and a little confused on pages 266 - 267 when he is talking about Routing for Networks (using RIP) and believe that this is for routing physically attached networks but he states networks 192.168.10, 20 and 30.0, but .10.0 isn't a directly attached network but is instead an ethernet segment attached via one neighbour link. Hopefully it is a typo but the Sybex website Errata doesn't say this.

I am 99.9% sure of this as the (config-router)#network x.x.x.x command is to tell RIP which directly connected network(s) to advertise and RIP will find remote networks for the rest of the table.

Getting there slowly but surely..... me hopes!

Thanks

dtlokee

The network command really does 3 things:

1. Tell the routing process what networks to advertise into the protocol
2. Tell the router what interfaces to send updates for the process
3. Tell the router what interfaces to receive updates on

So in the rip example you would only need to add network statements for directly connected networks and would have no effect on any networks that are not directly connected.

Slowhand

Yup, he probably meant that you should only include the .20.0 and .30.0 networks. Usually, RIP is demonstrated with a 10.x.x.x network, and they show you the example of simply doing (config-router)#network 10.0.0.0 to encompass all connected networks on the routers. My guess, is that Todd probably still had his head in the 10.0.0.0 network mindstate, and forgot to exclude the 192.168.10.0 address for the current class C example. (Those class A addresses makes the examples a lot easier to configure, that's why a lot of RIP examples use them.) Send off an email and explain the confusion, you might end up creating an entry on the errata page.

geezer

Thanks for the prompt replies folks!

Thought so but nice to have some clear thinking. He should then have put 192.168.40.0 as this was the serial link between LAB B and C rather than the ethernet I/F which had 192.168.10.0.

What would happen if you added RIP networks NOT on the local interfaces?

Slowhand

geezer wrote:

What would happen if you added RIP networks NOT on the local interfaces?

Nothing, really. All the existing routes would be advertised, the non-existing one(s) would be ignored. Although, if more than one router is advertising the same network and one of them doesn't actually have that network connected, there may be traffic problems down the road. I'm not 100% certain if this would cause an issue with RIP and IGRP or not, but I'm sure one of the Cisco heavy-hitters on the forum here can answer that one for us. The best policy is to only explicitly advertise routes that exist on the router.