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AS path filter

mohammedrafiq
Beginner
Beginner

                   Hi All,

Please see attached topology,

Router AS 200 have ebgp peering with AS 100 and also with AS2( which has direct peering with AS1) .We sending all the routes from AS200 to AS 100, but now

We have requirments at router in AS 200  that it only send route to AS 100 from AS2 and filter all the routes comming from   AS1.

I am thinking to use AS filter at AS 200 towards AS100 with regular expration, but not sure which one will serve this requirment.

Thanks and Regards,

3 REPLIES 3

Dan-Ciprian Cicioiu
Rising star
Rising star

Hi

a ) If the requiremnet is to advertise to 100 ONLY AS 2 :

ip as-path access-list 100 permit _2$

Permit AS2 , deny anything

b ) If you have also other prefixes , but you want only to filter AS 1:

ip as-path access-list 100 deny _1$

ip as-path access-list 100 permit .*

Deny AS1, permit anything

Either way apply the as-path acl on OUT to AS100.

router bgp 200

neigh AS-100-NEI filter-list 100 out

Dan

Thanks DAN,

AS 200 is also connected to lots of other AS's, and I need all thses router goes from AS 200 to AS100,but only want to drop routes from AS1.

Regards,

Hi,

so Dan's option B is what you need.

Regards.

Alain

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