route restriction on BGP

[Goutam Biswas]

Hi,

I have two MPLS links from two different ISPs are terminating on a single router and eBGP is configured between PEs and CE router.  We have some sites are connecting via 1st IPS's MPLS link and some other sites are connecting via 2nd Mpls link from 2nd ISP.  But terminating on same CE Router.

I am worried about, how do I confirm traffic from 1st link of 1st ISP should not leak to 2nd link from 2nd ISP and vise versa.  And also for forwarding traffic should maintain this.

Please give me some idea on this.

[milan.kulik]

Hi,

if you want to keep the MPLS clouds separated, just check carefully which prefixes you are advertising to each MPLS provider from your HQ site by the CE router peering to both.

If you advertise only the local site prefixes (with an empty AS_PATH), each provider will not get the prefixes from the other provider and your HQ will be reachable from both MPLS clouds.

You can easily configure

ip as-path access-list 1 permit ^$

!

route-map local_only permit 10
match as-path 1

!

router bgp ...

nei x.x.x.x route-map local_only out

nei y.y.y.y route-map local_only out

on your HQ CE router.

If you are not advertising default route or something similar from your HQ to the MPLS providers, only traffic with destination = your HQ should be delivered to your CE router.

Best regards,

Milan