16 Sep
2019
16 Sep
'19
3:55 p.m.
Peace, On Mon, Sep 16, 2019, 12:04 PM Owen DeLong <owen@delong.com> wrote:
For any router which receives both announcements, longest match always wins over all other BGP tie-breaking criteria.
This is almost always summarized as “Longest Match always wins” because virtually any engineer recognizes that the winner is selected only from the available contestants, not from unknown distant contestants not present at the router in question.
The point is that you must expect inbound traffic to any prefix you advertise to the outside world, even a more specific announcement is also being advertised. There are legitimate circumstances where an ISP would prefer the super-block. -- Töma