EIGRP External Route Path Selection

This topic is to discuss the following lesson:

Hi Rene
I have two notes about router one configuration :-
1 - In the configuration of external route – same AS number you need to advertising the 192.168.13.0 network or change the wildcard mask to 0.0.1.255 otherwise the router one and router three will not become neighbors.
2 - In the configuration of external route – different AS if you get rid of eigrp AS 1 we will lose the neighbor adjacency with router two.
please correct me if I wrong
Thanks a lot

Hi Hussein,

You are right, I left some errors in the configs…oops! Just fixed them, thanks :slight_smile:

Rene

No thanks to the duty :slight_smile:

Hi,

Is this External routes behaviour the same for Internal routes , i.e 2 different internal AS processes?

Cheers,
Rob

Hello Robert

External routes are defined as routes learned by an EIGRP process via redistribution. This redistribution can also take place from one EIGRP AS to another just like in the lesson. In the lesson, you can see that these routes are marked with the EX designation, meaning they are indeed external routes.

This behaviour of choosing the lower EIGRP AS as better takes place only when you have multiple AS’es configured within your EIGRP topology, and when the same route is learned from two different EIGRP AS processes.

Now when you say “internal routes, from two different internal AS processes” I’m not sure what you mean. All routes that are “internal” to a router, are those that are directly connected. Those are not learned via EIGRP, but are automatically placed within the routing table. All routes learned via EIGRP are learned from other routers. So you never have any “internal” routes learned via EIGRP.

I hope this has been helpful!

Laz

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Thanks for the explanation, I think I have my terminology mixed up here, I guess when there are 2 EIGRP AS’es, when they exchange ‘internal’ routes with each other, they will become ‘external’ (as they are external to the AS, so what I mentioned is not actually possible in hindsight (after your explanation).

Cheers,

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Um so your saying we should use Vrf and if we needed to set this up where it would work?

Hello Brian

Hmm, I’m not sure where you find that information. I don’t see any mention of VRFs in the lesson. Can you clarify? Thanks!

Laz

this is a post placed in wrong forums sorry can be deleted out. I dont remember the question as well which meant I was kind of just confirming something I already knew. However, does not go with this topic as I read through it three times just to make sure and this topic was about preference not about separating traffic or routing which is what VRF is.

Sorry!