EIGRP question

Brent Rockburn · ‎08-12-2010

In the pic you'll see the Eigrp link with 170 and the DMVPN link which is being seen as 90 (internal)

The problem I'm having is that when anyone wants to reach 10.69.0.0 /26 they're going through the DMVPN because that path is being seen as 90 where the MPLS is being seen as 170.

So if I do a "distance 70 10.69.0.0 /26" <-- yes I know I'll have to do the wildbits

will that make the MPLS the prefered path for that subnet?

Thanks,

BR

Jon Marshall · ‎08-12-2010

Brent

It's not entirely clear from the diagram but i'm assuming you are redistributing EIGRP from MPLS and so it is 170 and not 90. If so changing the distance to 70 would have the desired effect but remember that changing distance is local to the router you do it on so you would need to change it on every router that was affected.

Another way to approach it would be if you could summarise down the DMVPN link and not on the MPLS link so that the site receives more specific routes via the MPLS link. That way the more specific routes via MPLS would be used and only if the MPLS link failed would it then switch across the DMPVN link.

Changing distance is usually a last resort but it may be that you cannot summarise down the DMVPN.

Jon

gatlin007 · ‎08-12-2010

Brent,

I've run into this problem as well.

As Jon states altering the distance is not a great scalable solution and it is local to that router and not propagated. That said a common gottcha with the distance command it entering the routes you want to alter into the field that is actually the router-id field of the router advertising the prefix.

In regard to EIGRP you have another tool in the toolbox. The ablity to change the default admin distance for EIGRP internal and external routes. If you want them to be the same you can do that.

distance eigrp internal-distance external-distance

http://www.cisco.com/en/US/docs/ios/12_0/np1/command/reference/1reigrp.html#wp1017590

Chris

Mohamed Sobair · ‎08-12-2010

Brent,

your design is not clear , the DMVPN and the MPLS are not visible here. But In general, yes, In order for a router to prefer path over another, it uses the following methods:

1- prefers the path with longest Match first.

2- If there is a tie, it would prefer the path with the lower AD value.

3- If there is a tie, it would prefer the path with the lowest cost.

4- If there is a tie, it would performequal cost load balancing.

HTH

Mohamed