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. randy