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prakkdangc
Beginner

Losing BGP prefixes

Hi,

We have site that is only receiving ~2000 of the ~4000 prefixes we pump around the country. A sh ip bgp nei is showing a lot of inbound AS_PATH loops, but the PE vendor does not see any problem (he said). These sites are all "cookie cutter" deployments with the following similar configs:

router bgp 1111 (obvious fake!)

no synchronization

bgp log-neighbor-changes

network 10.x.x.1 mask 255.255.255.0

neighbor 10.x.x.2 remote-as 2222

distance bgp 200 200 200

no auto-summary

I am not sure where to start looking!

Any clues?

Dave

1 ACCEPTED SOLUTION

Accepted Solutions

Hi ,

you can test if this is the problem , by disabling this requirement : neighbor x.x.x.x allowas-in

If you will see your prefixes , then you will see also the as-path , and this is the answer to your problem.

Dan

View solution in original post

6 REPLIES 6
Marcel Zehnder
Participant

hi dave

Are all the CE's located in AS1111 and all the PE's in AS2222?

If there are that many AS-PATH loops and the scenario is like in my question - maybe the PE-vendor missed to configure "neighbor x.x.x.x as-override" on some of the BGP peerings to your CE's.

HTH

Marcel

Thanks Marcel,

There are several 1111's and 2222's. That's a great idea about the as-overide.. I will open a ticket with the provider and ask that question.

Dave

Hi ,

you can test if this is the problem , by disabling this requirement : neighbor x.x.x.x allowas-in

If you will see your prefixes , then you will see also the as-path , and this is the answer to your problem.

Dan

View solution in original post

Good point, Dan

That was very informative .. all the missing prefixes show up a path of  *> x.x.x.x. 2222 1111 ?

So I need to look at the configurations of other AS2222 routers to find my problem?

Dave

Yes - Enable AS-Override on every PE-to-CE-peering:

neighbor x.x.x.x remote-as 1111

neighbor x.x.x.x as-override

HTH