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Default route prevents NHT from working

I've got a campus MPLS network and I'm stuck with an EIGRP default route that I can't get rid of until everything is migrated to its proper VRF. This is causing me pains with BGP next-hop tracking. The core switches don't clear out the neighbor right away when the interface goes down. Let's say I want to remove the default route from the global routing table but keep default routing behavior, I was thinking of putting aggregated routes for all the IPv4 space, like 1.0.0.0/8, 2.0.0.0/8 ... 128.0.0.0/1 in my WAN distribution block pointing to the same next-hop IP as my default route, then remove the default route entirely from EIGRP. Is this approach been implemented before or is there a better way of doing it? I am using a Cat 6500 with a Sup 720, and selective NHT is not available :(

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Cisco Employee

Re: Default route prevents NHT from working

Hi,

Aggregate routes will not help. You will have the same behavior as with the default one.

If it's supported, you can try BGP Fast Peering Session Deactivation but it's useful for iBGP session only if there is no RR.

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

The behavior is the same as NHT except it focus on the neighbor address instead of the NH.

You can attach a route-map to this feature to select which routes to watch (like S-NHT):

http://www.cisco.com/en/US/docs/ios/iproute/configuration/guide/irp_bgp_neighor_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1054071

If it's not possible, you can always decrease the BGP timers for faster peer failure detection but be careful of the CPU impact.

HTH

Laurent.

New Member

Re: Default route prevents NHT from working

Thanks for your input Laurent,

I've decided to reduce the BGP timers.

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