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how to influence upstream BGP routers to control BGP path

rhienwei2010
Beginner
Beginner

Probably a lame question:

I have two routers connecting to two ISPs individually on BGP(same AS# at my side), I want to control which ISP link the Internet users will use to connect me.  How can I do that?  How can I control my BGP advertising to upstream so make one link is prefered to my IP subnet?

Thanks a lot.

1 Accepted Solution

Accepted Solutions

John Blakley
Advisor
Advisor

In this situation, AS Prepending may be prefered. Configure your non-preferred link by prepending your AS number a couple of times and apply outbound to your peer:

ip prefix-list LessPreferred permit 192.168.1.0/24

route-map LessPreferred permit 10

match ip address prefix LessPreferred

set as-path prepend

route-map LessPreferred permit 20

router bgp

neighbor route-map LessPreferred out

When the neighbor gets the advertisement from you, the less preferred route will have a longer as path and will be less preferred than the path through the other neighbor.

HTH,

John

HTH, John *** Please rate all useful posts ***

View solution in original post

5 Replies 5

John Blakley
Advisor
Advisor

In this situation, AS Prepending may be prefered. Configure your non-preferred link by prepending your AS number a couple of times and apply outbound to your peer:

ip prefix-list LessPreferred permit 192.168.1.0/24

route-map LessPreferred permit 10

match ip address prefix LessPreferred

set as-path prepend

route-map LessPreferred permit 20

router bgp

neighbor route-map LessPreferred out

When the neighbor gets the advertisement from you, the less preferred route will have a longer as path and will be less preferred than the path through the other neighbor.

HTH,

John

HTH, John *** Please rate all useful posts ***

Thanks a lot.

Dear John,

I need same require , we are using three different ISPs Bandhwdith in Single Router (eBGP) and our require as given bellow.

We have 1.1.1.0/24

              2.2.2.0/24

              3.3.3.0/24

but i need 2.2.2.0/24 ip pools traffice from ISP-3 i have confgured as-path prepend of this ip pools on ISP-1 and ISP-2.

ip prefix-list ISP-3 seq 5 permit 2.2.2.0/24

route-map ISP-3 permit 10

match ip address prefix-list ISP-3

set as-path prepend my asn my asn my asn

router bgp my asn

nei ISP-1 x.x.x.x route-map ISP-3 out

nei ISP-2 y.y.y.y route-map ISP-3 out

but not work properly we are using IOS - flash:c3845-ipbasek9-mz.124-24.T.bin in my Cisco Router.

Please help for the same and how can i achive this.

Thanks in ADV,

Hi,

have you done a route refresh ? clear ip bgp * out

Regards.

Alain

Don't forget to rate helpful posts.

Don't forget to rate helpful posts.

Dear Alain,

Yes i have done clear ip bgp * but not any effect , and i want to know this config is it right ?? or not to achive this ?? as per my requirement.

Pl help it is very URGENT for me...

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