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New Member

select exterior eigrp route over interior eigrp

hi,

so I have a setup where the core is connected to the remote site with 2 links.

1st link is a site to site wireless, so from core to remote site I have eigrp 100 going.

2nd link is an mpls, same eigrp 100 is being used expect that its being seen as a exterior eigrp most likely because the isp is redistributing my eigrp into something else and then coming back at the remote site as eigrp.

now I would like to give the priority to the exterior eigrp route because it's my mpls rather than the wifi which is a site to site.

I have tried using the distance on the core. so the interior (wifi) route is set to a AD of 254 and the core still uses the interor rather than taking the exterior route with AD of 170. the only time it uses the exterior is when I set the AD to 255 which is removed from the table but that's not what I want to do.

is there any way to tell this router "look buddy I know what I'm doing use the mpls route and not the wifi"

I have also tried on the remote location sending the routes to the core using offset but still nothing.

basically if the interior route is there no matter the AD it will use that one.

thanks.

I've attached a quick and dircty jpg file.

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4 REPLIES
New Member

select exterior eigrp route over interior eigrp

one thing that I've found is

on the core I setup a static saying

ip route "remote subnets" 192.168.1.1 250

on the remote I do

ip route "to core subnets" 192.168.1.2 250

now with this in place the mpls circuit is being used.

when I shut down the mpls circuit interface I'm still up because the static is being used.

I was just hoping to do the same thing with eigrp.

thanks.

Cisco Employee

select exterior eigrp route over interior eigrp

Hello,

Have you tried using the command distance eigrp 90 89? This should make the external routes preferred to internal by lowering their administrative distance to 89.

Your MPLS VPN provider is performing a series of EIGRP-BGP and BGP-EIGRP redistributions to carry routes between your sites. However, assuming that the provider is using Cisco devices (otherwise he would probably be unable to support EIGRP at all), they should already support the BGP ability to carry detailed information about EIGRP route types (internal and external) and their metrics. The net result should be that the routes visible on your sites should be only internal, and you should then be able to select the preferred route simply by influencing the usual EIGRP metrics (preferably, the delay component).

Ask your MPLS VPN provider about these two features, they should do the necessary trick:

http://www.cisco.com/en/US/docs/ios/iproute_eigrp/configuration/guide/ire_mpls_vpn.html

http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/s_mvesoo.html

Best regards,

Peter

Bronze

Re: select exterior eigrp route over interior eigrp

Sorry Peter, but changing the distance to prefer external over internal is not a good idea. The AD change will only influence RIB interaction but not internal EIGRP operation. Some of the topo table ordering logic knows about internal being better than external (independent of AD) and could be really hosed it you do the AD change you've suggested. It might kinda work sometime, but not consistently.

A better answer is to use another AS across the wireless link and do controlled redistribution (probably using tags) so the comparison becomes external against external. Remember that EIGRP to EIGRP redistribution will retain metrics if you don't specify a redist metric so shortest path will be used. Just be careful and use tags to stop routing loops or count to infinity problems.

I also agree that if the service provider supports the PE-CE VPN feature (which I happened to commit) that would also work because then it would be comparing internals to internals.

Sent from Cisco Technical Support iPad App

Cisco Employee

Re: select exterior eigrp route over interior eigrp

Hello Don,

Thanks for joining!

In fact, I do not like the AD modification myself, but to be honest, I was following your insight from the thread in which we've discussed the influence of AD to the EIGRP's selection of best paths:

https://supportforums.cisco.com/thread/2096235

(I was kind of hotheaded in that thread - I sincerely apologize for that)

After reading your comments in that thread, I thought that it would be actually safe to modify the AD (while taking into account all the obvious disadvantages of this approach, such as this AD modification is local only). Now you're saying that the issue is more complicated than that. Hmmm... You always bring out some jewels of knowledge about the EIGRP.

Anyway, the idea with the another AS is very nice! And - oh - it was you who committed the PE-CE VPN feature? Wow!

Best regards,

Peter

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