Two router interfaces in same EIGRP AS

[Paul]

Hello - I am curious if it is okay/best practice to configure two interfaces on the same router (two different ISP circuits) in the same EIGRP AS?

Will EIGRP manage the routes for both interfaces just fine? Reading online I've come across this FAQ:

http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/13681-eigrpfaq.html

where it mentions to not have the same interface in two different EIGRP AS, however I'm trying the opposite. Logically I believe it to work, however i wanted to discuss this setup.

TIA

[rasmus.elmholt]

Hi

Often you have more interfaces in the same EIGRP AS, when you a routing with EIGRP. So this is a valid solution in your case.

The FAQ says you shouldn't have the multiple AS'es on the same interface, where you ask for the same AS on multiple interfaces

.

[Richard Burts · Accepted solution]

You are correct that what you are trying to do is pretty much the inverse of what that link was talking about. In general it is no problem at all to have two (or more) router interfaces in the same AS. In fact it is the most common practice for a router to have a single AS and to activate multiple interfaces in that AS.

However there is a potential issue in what you describe which you should consider. From the EIGRP perspective it is no problem. But the fact that these are ISP interfaces raises several questions that you should consider:

- will the first ISP run EIGRP with you? Will the second ISP run EIGRP with you?

- if both ISP are running EIGRP with you in the same AS then do you want to take routes that you learn from ISP1 and advertise them to ISP2?

HTH

Rick

[Paul]

Thanks, Richard.

The ISP hand offs are both layer2 circuits and allow me to run my own EIGRP AS.

[Paul]

Also, yes - I want routes from both interfaces in the EIGRP AS to be able to speak to one another, these are private WAN circuits, the only networks on the far end of the link are my own L3 routers.

[Richard Burts]

Thanks for the clarification. If these are private WAN circuits and your L3 routers are connected on the remote end then having both interfaces active in EIGRP same AS is very appropriate and is not a problem.

HTH

Rick