Advanced BGP Route Reflector

[cIsCoHector]

Hello expert guys

I was wondering if you know some techniche were a bgp route reflector can make local decisions ( chossing prefixes based on attributes) and not affecting his route reflector clients due to that desision, I'm using IOS 12.4(5) and I would like to know if this can be possible on this version. Thanks in advance

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[AJ Cruz]

Local preference is a locally significant attribute. What specifically are you trying to do? You can always reset attributes as you advertise them to clients.

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[AJ Cruz]

Sorry, weight is locally significant, local pref is for the local AS

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[Giuseppe Larosa]

Hello Hector,

a route reflector server propagates only the BGP best path, you cannot have a device that makes a different choice for itself and propagates a different path to clients.

If you manipulate BGP attributes to prefer one BGP route over another the first will be propagated to all client and all non clients.

There are some tricks that can be used with VPNv4 prefixes to avoid best path selection at route reflector server ( that is to use different route distinguisher on colocated PE nodes for the same multihomed VRF site) and have it to propagate all different advertisements.

Hope to help

Giuseppe

[cIsCoHector]

Thanks Giussepe

In fact i am looking for a solution when i modify the best path on route reflector, in this case using bgp bestpath aspath ignore on server and this not modify the clients decision I think this is not possible as you comment, can you share any doc about your solution with rd? Thanks in advance

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[narainarun]

Hi,

Whatever Giussepe said is a valid option of having differenet RD (which eventually makes a single prefix to two unique VPNV4 prefixes).

BGP "Add-Paths attribute" is a new feature where BGP speaker can advertise multiple prefixes  (without choosing the best one and advertise) to its clients and non-clients. It adds a "Path Identifier" for every prefix and advertise it and the local edge router can make a decision. Its a work in progress in IETF.

Guissepe - I would like to know if I have two RR clusters with each cluster having different route selected and the edge routers peering with this two different RR clusters. In that case, the edge routers can have both entries in its BGP table and can choose the route accordingly?

thanks

Arun

[Giuseppe Larosa]

Hello Arun,

>> I would like to know if I have two RR clusters with each cluster having different route selected and the edge routers peering with this two different RR clusters. In that case, the edge routers can have both entries in its BGP table and can choose the route accordingly?

Yes, at that point the edge routers could receive from each cluster a different BGP advertisement and could install both routes if they are different (different BGP next-hop ) if configured appropriately

Hope to help

Giuseppe