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Community Member

BGP filtering help

I have the following route-map applied in-bound:

ip prefix-list DENY_BAD_ROUTES seq 10 deny 0.0.0.0/8 le 32

ip prefix-list DENY_BAD_ROUTES seq 20 deny 10.0.0.0/8 le 32

ip prefix-list DENY_BAD_ROUTES seq 30 deny 127.0.0.0/8 le 32

ip prefix-list DENY_BAD_ROUTES seq 40 deny 172.16.0.0/12 le 32

ip prefix-list DENY_BAD_ROUTES seq 50 deny 192.0.2.0/24 le 32

ip prefix-list DENY_BAD_ROUTES seq 60 deny 192.168.0.0/16 le 32

ip prefix-list DENY_BAD_ROUTES seq 70 deny 224.0.0.0/3 le 32

ip prefix-list DENY_BAD_ROUTES seq 1000 deny 216.x.x.0/24 le 32

ip prefix-list DENY_BAD_ROUTES seq 9999 permit 0.0.0.0/0 le 27

As well as the following filter-list:

neighbor 12.117.191.169 filter-list 5 in

!

ip as-path access-list 5 permit ^7018$

My goal is to accept default plus local routes from AT&T (AS7018) via this connection, but somehow I believe I'm only getting default.

How do I check for sure whether I'm getting the other routes? Here's the result of a received-routes query:

router#sho ip bgp nei 12.x.x.169 received-r

BGP table version is 3, local router ID is 172.31.204.20

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*> 0.0.0.0 12.x.x.169 0 0 7018 i

Total number of prefixes 1

Thanks,

/rls

4 REPLIES
Community Member

Re: BGP filtering help

To add to my post above, I'm assuming that I should see other routes or prefixes other than 0/0. AS7018 has ~20k local routes I'm told.

/rls

Bronze

Re: BGP filtering help

Are you 100% sure AT&T is advertising you routes. Its very common to only advertise a default route unless the customer requests full or partial routes.

Community Member

Re: BGP filtering help

cpubob,

That's the main question I'll be asking tomorrow. I've been so stuck on looking at my config that I didn't stop to think that they might be filtering everything down to just 0/0. Thanks for questioning.

/rls

Re: BGP filtering help

Hi Robert Samuel,

You need to ask AT&T if they are advertising to you only default route.

To peer with an upstream, you need to request for either full route or partial route. This is beneficial if you are multihoming. Else, default route is enough if you only peer with AT&T. However, even though you only peer with AT&T, you can still request for full route or partial route.

Dandy

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