EIGRP failover preferring BGP (eigrp-external) route over eigrp-internal

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Jan 3rd, 2008
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Hi,


It appears there are multiple ways to tackle this, so appreciate any validation as i am unable to recreate in lab and would like to be better prepared before trying on production.


We are in the process of setting up failover for a remote site for connectivity to the HUB.This remote site will connect to the HUB through 2 different carriers (the carrier routers are ISP managed). Pls review attached diagram


Question is .. that once the routes from the REMOTE site hit the hub - we want to prefer routes from Carrier 2 (which is coming in as BGP - EIGRP-external) as primary. If that fails, we want routes from Carrier 1 (EIGRP-internal) to come into place


My understanding is that unless some tweaks occur - the reverse will happen. In that the HUB will prefer EIGRP-internal routes from Carrier 1 as it has lesser admin distance.


How do we ensure that the primary is Carrier 2 (EIGRP-external)


We do not have a situation where a site connects to 2 carriers to the same hub until now. Attached below is sample output i noticed at the hub for 2 different sites using the 2 carriers so i can guage what metric/distance the routes come in as.


One possibility i am thinking is to setup DELay at the interface level for Carrier 1 - and have those as redistribute connected at the REMOTE LAN gateway. that way we ensure all routes come into the HUB as EIGRP-EXTERNAL and then based on DELAY for carrier 1 .. the routing tables will install the lesser delay'ed Carrier 2


Is this an optimal approach ?

THANKS much

aram



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Collin Clark Thu, 01/03/2008 - 11:42
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Arathy-


How about using a route-map on your router(s) and adjusting the metrics to make the MPLS network preferred?

arathyram Thu, 01/03/2008 - 12:04
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Thanks CE. I am checking into that as well. The issue i ran into is that at the HUB MSFC both the carriers come into the switch portion of the MSFC on the same vlan. We did some tests in the lab and were able to apply route-maps at the interface level, but since in production - the carrier WAN routers are connected on the same vlan - i was unable to implement. I am researching if the route map can be setup based on which IP/wan router to prefer routes from


also, what we noticed in the lab is that when we apply the route map to the lab-hub router - it would momentarily recalculate eigrp. So, just being cautious in that if we did this in production - momentarily we'll take the HUB down for all sites

Collin Clark Thu, 01/03/2008 - 12:09
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Yes EIGRP will recalculate and traffic will start to flow over MPLS. Instead of using VLANs check out using routed ports on your 6500. There will have to be some IP renumbering, but it will make things easier in the long run.


HTH

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