Multihomed route visibility

Mon Nov 4 16:23:22 UTC 2019

> On Oct 31, 2019, at 3:12 PM, Boyle, Patrick via NANOG <nanog at nanog.org> wrote:
> 
> We are advertising the same prefix to ISP A & ISP B. When looking at various route servers across the world, I always see the path through ISP A in the BGP table, but most don’t show a path at all through ISP B (some do, like Oregon IX). I would expect any router with the full table to show both routes. Is this a consequence of how the route servers are peered up? Are they only displaying the preferred path? ISP Issue? Am I missing something?
>  
> Any help would be appreciated.

You will generally only see the best path.  Most route servers don’t collect any backup paths the routers may have, which could be quite extensive.

- Jared