On Mon, Nov 4, 2019 at 8:13 AM Boyle, Patrick via NANOG <nanog@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?
Hi Patrick, Routers only propagate the *best* BGP route for the target network. You'll see both only where the AS received different best routes from its peers. Regards, Bill Herrin -- William Herrin bill@herrin.us https://bill.herrin.us/