Routing

Hello folks

I got one question. Our AS is connected to two different AS (transit AS) say AS1 and AS2 and these AS also connected to each other and other transit AS well. So these AS1 and AS2 sending the same coppies of routes to our AS with their own AS routes.

I want to change the prefernce of these transit routes so that traffic from my AS for these transit routes (except the self generated routes in AS1 and AS2) always chose AS1.

I woudl appreciate if any one can give me the hint for this?

Thanks

Hi,

You can have an import BGP policy which sets higher  local-preference for neighbor AS1. However, be sure to have a term accepting routes originating from AS2 and AS1 before the local-pref term. I've given one example below

policy-statement EBGP-IN {
    term Peer-Originated {
        from as-path [ AS1 AS2 ];
        then accept;
    }
    term Local-Pref {
        from neighbor 10.1.2.2;
        then {
            local-preference 110;
        }
    }
}
as-path AS1 ".* 65002";
as-path AS2 ".* 65003";

You need the first term because, as per the BGP route selection, local-preference will have higher precedence over AS-Path. Hence, if you do not have the "Peer-Originated" term, you may end up selecting AS1 for the routes originated by AS2 which will be sub-optimal and undesirable. 

Also, make sure to have any discard related terms placed before the "Peer-Originated" term in your EBGP-IN policy.

Please accept the solution if it works 🙂

Rgds,
Pavan Kurapati

 JNCIP-M

Thanks buddy