bgp influence inbound route

Unanswered Question
Jul 12th, 2007


we config the bgp to influence inbound traffic. the config is following.

We would like 202.x.7 come in PA (provider A) and 202.x.10 come PB (provider B). In US site, we have one Internet circuit. we find that four ip address always goes to "provider B" even we add ten AS number append to it. any idea to influence the inbound traffic to go different circuits in HK? pls advice

router bgp 1234

neighbor 202.1.w.129 filter-list 200 out

neighbor 202.1.y.1 route-map Set_ASN_PB out




access-list 40 permit 202.x.7.0


access-list 50 permit 203.x.8.0

access-list 50 permit 203.x.9.0

access-list 50 permit 203.x.10.0


ip as-path access-list 200 permit ^$



route-map Set_ASN_PB permit 10

match ip address 40

set as-path prepend 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234


route-map Set_ASN_PB permit 20

match ip address 50


route-map Set_ASN_PB permit 30

! match as-path 200

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sundar.palaniappan Thu, 07/12/2007 - 13:47


Can you check the routes on one of the public BGP servers on the Internet to see whether the prepended AS Path still exists for that particular route. It's possible providerA might be summarizing the routes and advertising it out to the Internet whereas providerB might be advertising that network as it is and that would cause providerB to be the preferred path for that network despite the prepended AS path. Talk to providerA about this and they should probably be able to help you with this.

If you are still having issues can you provide more info about the problem for us to find the issue.



leungcm Thu, 07/12/2007 - 14:02


if we annonce only one route (203.x.7.0/24) to "provider B" and do not annonce another routes. the traffic can come to different circuits.

which providers problem? how to solve it? pls advice

best regards

sundar.palaniappan Thu, 07/12/2007 - 14:49

Did you look up on any public BGP server the route to your network. It could be how providerA advertising your network out to the Internet may be the problem. As I stated before you would definitely want to talk to providerA as their involvement may become necessary here. It appears you don't want to reveal your public address and that makes us unable to do the route lookup ourselves.



leungcm Thu, 07/12/2007 - 19:00

We get following infon after the test. Anything can "provider A" do to solve this issue? thanks

provide B


Origin IGP, metric 0, localpref 300, valid, internal, best

provider A


Origin IGP, metric 600, localpref 199, valid, internal, best

leungcm Fri, 07/13/2007 - 07:57


anything wrong in provider A? please advise

Best regards


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