RIP Functionality

[admin_2]

Hi

I have the following scenario.

10.10.10.0/24-----RtrA---192.168.10.0/24---RtrB---10.10.20.0/24----RtrC---10.10.30.0/16

Question?

What is the routing table for routerC.Will RouterC learn the network 10.10.10.0/24?If yes,why and if no..why?

All the routers are running RIPv1.

As to my level of understanding,Router C will not learn the network 10.10.10.0/24 since the routerA will act as classful boundary for 10.10.10.0/24 network and will advertise route as 10.0.0.0/8.Since Router C is connected direclty for 10.10.20.0/24 network it will assume that network and will not update the routing table for the advertised route.

Please provide me your inputs??

Regards

[Richard Burts]

You are correct. If the routing protocol is RIPv1 then part of the behavior of RIP is automatic summarization at network boundaries. rtrA will advertise to rtrB the summary 10.0.0.0 (on the interface for 192.168.10.0). rtrB does not learn 10.10.10.0 and certainly can not advertise it to rtrC.

If the protocol were RIPv2 there is an option to turn off automatic summarization which would make this network workable.

[rais]

If routerA had'en 10.X.10.0/24, where X is not = 10, you would have seen the traffic move between A and C.

Regards.

[Harold Ritter]

you would have the same issue no matter subnet you would use in that same major net.

[Harold Ritter · Accepted solution]

Your understanding is correct. Router A will be sending 10.10.10.0 as classfull network (10/8) since it is crossing a major net boundary. So B will not see 10.10.10.0/24. One way to fix that is to either replace the ip address between router A and B by and address that would allow 10.10.10.0/24 to be sent as such or to configure a secondary address who would play the same role.

Hope this helps,

[#6]

Hi

Thanks very much for the information.It certainly did not work.Rtr C did not receive any updates from rtr A.However,after configuring a secondary address with 10.x.x.x/24 between rtrA and rtrB,the updates were received by rtrC and traffic was moving accross the routers.

My general understanding for RIPv1 is that,there should be uniformity in subnet mask and major class network for RIPv1 to receive updates.

Thanks very much.

Regards

[rais]

I agree with hritter.

Thanks.

[dmitchell1975]

Along with the summarization along classful boundaries idea there is another rule that will apply. The rule is that the interface will apply the subnet mask configured of the interface which received the network information update from RTR A. If you had configured a mask of /24 on the receiving interface of RTR C (and all of interfaces if you knew what you were doing), then the network would be interpeted as 10.10.10.0/24. This however is the only case in which the intended mask would be applied.