Max Prefix Out, was Re: Verizon 701 Route leak?

Randy Bush randy at
Sat Sep 2 07:27:03 UTC 2017

>>>>> i have 142 largish bgp customers, a large enough number that the
>>>>> number of prefixes i receive from them varies annoyingly.  how do
>>>>> i reasonably automate setting of my outbound prefix limit?
>>>> First, it seems you know the inbound so automating the outbound is
>>>> simple arithmetic.
>>> I would have said the same... i ought to know high-water marks for
>>> your inbound peer count(s), and can work out a +20% outbound...
>> you just assumed that the transitive closure of everybody's cones
>> implement and propagate count.  ain't gonna happen.
> I am not sure what the issue here is. If I can tell my peering partner
> a recommended maximum prefix value for them to set on their side,
> surely I can configure that same value on my side as the upper
> outbound limit.

which is why i do not tell peers a max count.

this stuff works for small isps, in the lab, ...  but not at scale;
especially when you have isps as customers.  i wish it did.

bgp at scale is rather dynamic.  i suspect your $dayjob's irr filters
being exact help a bit.


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