EIGRP/IGRP backward compatible??? 1

[fluid11]

I read that EIGRP and IGRP are backward compatible with each other, and I was wondering if it was true or not? I have a subnet where all of the routers are running IGRP. I brought up a new router running EIGRP using the same autonomous system number as the IGRP routers, and they did not exchange routes. Is it possible to run a mix of EIGRP and IGRP or do I need to run IGRP on all of the routers?

Chris

 

[ccie9545]

they are compatible under certain conditions. first, you must ensure that all subnet mask are consistent throughout the network, cause IGRP does not support Variable Length Subnet Masks. That would probably be the most likely culprit. My suggestion would be to run EIGRP throughout teh network rather than IGRP..... Erik Rudnick, CCIE No. 9545
mailto:erik@kuriosity.com

 

[fluid11]

I'm trying to run IGRP and EIGRP on the same networks with the same masks...

192.168.x.0
172.16.x.0

All subnets are 255.255.255.0.


Chris

 

[Piass]

If you ask me, you're asking for trouble trying to run both. Try a proper protocol like OSPF OR IS-IS.

 

[fluid11]

I know all about that. I just need to figure out how to run them both on the same network.

Here's a very simple scenario...

RouterA - IGRP for 192.168.1.0/24 and 172.16.1.0/24
RouterB - EIGRP for 192.168.1.0/24 and 172.16.1.0/24

Will the above routers exchange routes with each other?

Chris

 

[ccie9545]

no, they will not share routing updates. you need to have both routing protocols running on a single router so that they can be redistributed.....if they are running on the same router and have the same AS number they will automatically redistribute. If teh AS number is different you will have to use the redistribute Erik Rudnick, CCIE No. 9545
mailto:erik@kuriosity.com