RIP Version 1 and 2 Comptability

[turbo_engine26]

Hello all,

As per the uploaded topology, i configured 3 routers to run RIP v2 and 1 router to run RIP v1. As you see, RTA and RTB  are connected to the same subnet as RTC. If i configure RTA and RTB to send and receive RIP v1 with RTC, the result is that both RTA and RTB are talking version 1 as well.

Then, i tried to configure RTA and RTB to just send only RIP v1 but they won't listen anything from RTC and they will learn the routes via RTD instead of RTC. For exampe, RTB will learn 192.168.2.96 subnet from RTD with 2 hop metric then RTA will learn that route from RTB with 3 hop metric. This is of course is not desirable. No problems in RTD and RTB, they talk RIP v2 and RTD talk RIP v1 with RTC because RTD and RTC in a point to point link.

How can i make RTA and RTB to communicate with RTC properly?

Another question please.

Since RTD has 2 paths to 192.168.2.64/28 (via RTB and RTC), which path should RIP choose? .... In static routes, you can drive the routes more freely than in dynamic routes.

Appreciate your valuable response.

[Peter Paluch]

Hello,

With respect to your first query, can you please issue the debug ip rip on both RTA and RTC and post the results here? Perhaps there is the information we are looking for that prevents RTA from learning paths through RTC.

Since RTD has 2 paths to 192.168.2.64/28 (via RTB and RTC), which path should RIP choose?

Both, of course, as they are both best routes. They should both be placed into the RTD's routing table and RTD will use them for load balancing purposes.

Best regards,

Peter

[turbo_engine26]

Hello Peter,

Thanks for the reply and glad to have you back.

I attached them as requested

[Peter Paluch]

Hello,

Thank you - I am glad as well

The RTA seems to suggest that it does not like the RIPv1 messages simply because of their version. It looks as if RTA was not really prepared to receive RIPv1 packets. How exactly did you configure the RTA and RTC with respect to RIP and versions? Posting the RIP and interface configuration sections from both routers would be most helpful. Also please include the show ip protocols output from both RTA and RTC.

Thanks!

Best regards,

Peter

[turbo_engine26]

Ok no problem ... i attached the config of the 3 routers.

But wait, i am not actually complaining about RTA can't communicate with RTC as i know the reason. I am complaining about how can RTA and RTB talk v1 with RTC without RTA and RTB talk v1 with each other? ... I mean is it possible to make RTA and RTB talk v2 with each other and v1 with RTC only? ... However, i tried to configure both RTA and RTB to send and receive v1 in order to talk to RTC but both routers (RTA and RTB) ended up they talk to each other in v1 as well as with RTC

[Peter Paluch · Accepted solution]

Hello,

Oh, I see. Sorry for the misunderstanding.

Well, as RIP is not configured in a per-neighbor fashion, what you are trying to achieve is quite difficult. You want:

• bidirectional RIPv1 communication between RTA/RTC and RTB/RTC
• bidirectional RIPv2 communication between RTA/RTB

This means the following:

• RTA and RTB must send their packets in RIPv1 so that RTC can understand those
• RTA and RTB must also send their packets in RIPv2 so they can speak to each other
• RTA and RTB must accept both RIPv1 and RIPv2 to accept packets from each other and from RTC

This will, quite understandably, cause the RTA and RTB to exchange information over RIPv1 as well as RIPv2.

My only solution at the moment is to force the RTA and RTB to send all their packets both in RIPv1 and RIPv2 using the interface-level configuration command ip rip send-version 1 2 and additionally, use an ACL to prevent mutual exchange in RIPv1. So for example, on RTA and RTB:

access-list 100 permit udp host 192.168.2.67 host 255.255.255.255 eq 520
access-list 100 deny udp any host 255.255.255.255 eq 520
access-list 100 permit ip any any
interface FastEthernet0/1
 ip rip send-version 1 2
 ip access-group 100 in

This way, you will allow RTC to understand your RIPv1 packets while at the same time, prevent RTA and RTB from communicating via RIPv1.

Best regards,

Peter

[turbo_engine26]

Hmmm, access list? .... I am sure it will work but please let me know if is there any other way using the only ip rip send/receive command. The problem with access list is it adds more processing overhead on the router every 30 seconds whenever an update is triggered but of course thank for your effort.

Just a curious question

Is there any issue if i run both RIP v1 and RIPv2 on RTA and RTB? ... I mean let's weight the overhead on the router when i use access list or when i use both versions on RTA and RTB. i am sure that both versions will create more update traffic on the links. On the other hand, access lists will create more processing time.

So, More processing Vs. More traffic on slow links

What do you think? ..

Thanks a lot

[turbo_engine26]

By the way, all of the topologies that i posted here are from an official CCIE book. I just want your opinion about this book and tell me if it is slightly misleading. I said misleading because whenever i post a topology i get feedbacks that it is unlogic or difficult topology.

The book name is : Routing TCP/IP volume 1 , second edition.

Please let me know if it is good book to prepare for CCIE lab.

Thx

[cadet alain · Accepted solution]

Hi,

This book is indeed a very good book to read  for CCIE RS but it is not a best practice or design guide so the topologies are used to demonstrate concepts not to be used in real life.

Furthermore the CCIE lab is not about real life nor simplicity but it is designed so you can demonstrate your knowledge of rhe protocols so the questions and/or topology might seem unlogic or overly complicated but that's the game.

Regards.

Alain.

[Peter Paluch]

Hello,

I take Alain's word for granted I haven't read the book

Nevertheless, can you post the exact assignment from the book about the RIPv1/RIPv2 cooperation? I need to understand what the requirements and the limitations are. Thanks!

Best regards,

Peter

[turbo_engine26]

Sorry for the late reply.

The assignment says the following:

Configure the four routers in the figure (the topology attached) to run RIP. RTC is running IOS 10.3 and for corporate reasons cannot be upgraded, therefore can only run RIP v1.

That's all

The trick in this book that when you examin the "Case Study: RIP Comptability", the topology is much simpler than the topology in the exercise. In the case study's topology, there is only one router can talk RIP v1 to another router. However, in the exercise, there are two routers should speak RIP v1 to another router.

BTW, i tried the access list solution and it is working as expected but what if in the CCIE lab access list is prohibited to be used in this scenario? ...

Thanks a lot for your help.

[er.vansh17091]

Hi,
I know its old thread but I have a question like can you please let me know, can we run RIP V1 & RIP V2 on the same router? If yes then how? if not then why not?

It is true that properties are different both of them..!

[xei292929]

Hi er.vansh17091,

Yes you can. 

Whatever version of rip your router is configured. 

You can still cahnge the behavior of rip on a per-interface basis.

Just issue the command: 

ip rip send version X

ip rip receive version x

Replace X by the version you want to be enabled on the interface.

You can run both version 1 and 2 also. Hit the question mark at the end of the command.

You can also see what version you are running on each interfaces with the show ip protocols command.

hope it helps.