[c-nsp] BGP route influence question related to multi-path iBGP

David Hubbard dhubbard at dino.hostasaurus.com
Fri Jan 20 12:49:10 EST 2017


Ah, perfect, and so obvious now that I think about it.  Easy to fix too as they already have an IGP on those links.

Thanks!

On 1/20/17, 12:38 PM, "Gert Doering" <gert at greenie.muc.de> wrote:

    Hi,
    
    On Fri, Jan 20, 2017 at 05:10:56PM +0000, David Hubbard wrote:
    > Hello all, I have a setup where one BGP AS exists at two physical locations, with an edge router at each location peered to different upstreams.  The two edge routers are interconnected with a 40gig and 10gig link, each with its own interface/address, so there are two iBGP sessions between the same two routers.  The intent of the 10gig is only to be used as backup, and when I first brought it up, the routers of course began treating them as equal cost paths (from BGP perspective) and used both.  The way I initially worked around that was via a route map on both sides that assigns a higher non-default weight to advertisements coming in via the iBGP session on the 40gig link.
    
    "The normal way" to do iBGP is "between loopbacks" and have an IGP 
    distribute loopback reachability across available links.
    
    Which will automatically achieve what you're asking for :-) 
    
    gert
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