1721 How to setup IGRP

[john.mccarthy]

My router does not show IGRP but ISO-IGRP as a option. My IOS is like 12.7 or 12.3 I think. Just got the router new last week.

[Richard Burts]

Cisco has dropped IGRP support from the IOS. There are other protocols available that do the same things (and do it better) that you could configure. If you really want a Distance Vector like IGRP was then run RIP (or RIP2). If you want Cisco proprietary like IGRP was then run EIGRP.

Is there a particular reason that you wanted IGRP?

HTH

Rick

[john.mccarthy]

I just used IGRP on my old 1601 and first few 1700 models. I noticed somthing called OSI-IGRP but after I iniated the command it said the software module was not loaded. Do you or anyone else no if OSI-IGRP replaced the IGRP? If I see it but the software is not loaded do you know how I can obtian it and load it on the server?

Thanks Sir... John McCarthy

[Richard Burts]

John

You do not want OSI-IGRP. If you really want to run IGRP to be compatible with your 1601 then you should load an old IOS on your new router.

As I said, I think that you should consider running a protocol that still has support from Cisco. Cisco has stopped including IGRP as a supported protocol. It will still run ok if you get an IOS version that is old enough, but why not look to the future instead of back to the past?

HTH

Rick

[john.mccarthy]

I agree. I plan to continue to use RIP and will stop using IGRP. What is you feeling on EIGRP as a substitue?

[Richard Burts]

In general I think that EIGRP is an excellent substitute. EIGRP is very much an improvement over IGRP. The choice of what is the best routing protocol depends very much on your local situation and on what are your criteria for measuring. I believe that in most situations EIGRP is a better choice than RIP.

There are a few situations I have seen where RIP was the best choice. Mostly these have been situations where there was some device in the network which needed to participate in routing and RIP was the protocol it ran (in the early days of the IP stack on the IBM mainframe that was the case, on some servers with dual NICs and Windows operating system it was the case, and there are others). I saw a situation where the customer wanted to keep one part of the Enterprise network somewhat separated and be able to control very carefully what was advertised to and from the rest of the network. The solution was to run RIP in this small part of the network and EIGRP in the rest of the network and redistribute between them.

In comparing RIP and EIGRP I would say that RIP is very easy, is well documented (there are RFCs describing RIP but not EIGRP since it is Cisco proprietary), and does very well with interoperability with other vendors gear. But it does use more bandwidth than EIGRP, is much slower to converge than EIGRP, does not give you as much flexibility in doing summarization, and its hop count limit of 15 makes it much less scalable than EIGRP.

For a simple lab environment RIP is good, but for almost all production networks I would choose EIGRP.

HTH

Rick

[vcjones]

As long as you mean RIP version 2 when you say RIP, there is no problem with using RIPv2 in a simple network. It works well and the efficiency difference compared to EIGRP or OSPF won't matter in a small network (up to a few dozen subnets being routed).

If your network is large (hundreds of subnets or many parallel/redundant paths) you will want to use a modern routing protocol, either EIGRP (if a Cisco only network and you don't have the time or energy to work out an efficient hierarchical design) or OSPF. Each has significant advantages and potentially critical limitations that you need to be aware of or you will have problems as your network grows. Either can handle a small network without much thought.

Good luck and have fun!

Vincent C Jones

www.networkingunlimited.com