Setting sensible max-prefix limits

Steve Lalonde steve at
Wed Aug 18 09:46:34 UTC 2021

On 18 Aug 2021, at 10:33, Lars Prehn <lprehn at <mailto:lprehn at>> 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?
> Apart from your peers, do you also apply a limit to your transit sessions?

We always use PeeringDB data and refuse to peer with networks not in PeeingDB ( I think there are only 2 exceptions ) Automation keeps the max_prefix numbers up to date. 

Our transits we use data from the weekly routing table reports and allow some expansion room.

So far this works for us


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