On Wed, 18 Aug 2021 at 11:33, Lars Prehn <lprehn@mpi-inf.mpg.de> wrote:
As I understand by now, it is highly recommended to set a max-prefix limit for peering sessions. Yet, I can hardly find any recommendations on how to arrive at a sensible limit.
I guess for long standing peers one could just eyeball it, e.g., current prefix count + some safety margin. How does that work for new peers? Do you negotiate/exchange sensible values whenever you establish a new session? Do you rely on PeeringDB (if available)? Do you apply default values to everyone except the big fishes?
- review max prefix suggestions from the peer itself, either from the email or peeringdb - check actual current prefix count (bgp.he.net et all) - check whether the disparity between the two matches your expectation of a safety margin, based on your own operational experience and context - defaults for low prefix count peers - actually monitor warning/critical levels of max-prefix counts Don't use too small a safety margin, you don't want to spend your days adjusting max-prefix levels all the time. I don't have strict rules for the safety margin itself; it depends very much on the network (size, growing rate, trust, history). lukas