[c-nsp] Redistributed EIGRP Route Preferred over EBGP?

[Chris Mason]

> When EIGRP is redistributed to BGP the Cost Community is added to the prefix - it's basically FD for EIGRP.

This is where I think the problem is, but didn't believe that CC was
compared until later down the BGP Path Selection Algorithm - by
setting weight I preferred a path before that comparison was made:

As per CCO (http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/s_bgpcc.html):

The cost community attribute influences the BGP best path selection
process at the point of insertion (POI). By default, the POI follows
the IGP metric comparison.

> If router compares the prefix containing the Cost Community with the same prefix but without CC the default CC (which is 2^31+1 = 2147483649) is used. In that case your EIGRP learned route wins.
>
> I can bet that you have a route loop in your network right now and the EIGRP route is announced back to the originator through BGP. I think that because your CC is quite high.
>
> You can check if the number of BGP table increases or if the hop count is increasing in eigrp topology for that prefix.
>
> The solution is just to set Cost Community to any low value on import from BGP with route-map. This should be done for redistribution from any protocol to MP-BGP (incl. static and connected) with EIRGP on PE-CE
> rotuer bgp <AS#>
>  address-family ipv4 vrf <vrf>
>  neighbor 192.168.2.2 route-map RM-SET-COST-COMM in
>
> route-map RM-SET-COST_COMM permit 10
>  set extcommunity cost pre-bestpath 1 100

I will give it a try and see if it resolves the problem.

Thanks,
Chris