On Fri, Jun 05, 2020 at 10:20:00AM -0700, William Herrin wrote:
On Fri, Jun 5, 2020 at 9:49 AM Saku Ytti <saku@ytti.fi> wrote:
The comparison isn't between full or default, the comparison is between static default or dynamic default. Of course with any default scenario there are more failure modes you cannot route around. But if you need default, you should not want to use dynamic default.
It's a little more nuanced than that. You probably don't want to accept a default from your transit but you may want to pin defaults (or a set of broad routes as I did) to "representative" routes you do accept from your transit. By "pin" I mean tell BGP that 0.0.0.0/0 is reachable by some address inside a representative route you've picked that is NOT the next hop. That way the default goes away if your transit loses the representative route and the default pinned to one of your other transits takes over.
I do the above using routes to *.root-servers.net to contribute to the aggregate 0/0.