Hello Pedro.
Firstly, which version of BIND are you running?
Generally, though, increasing `recursive-clients` on a box with a decent amount 
of power and RAM is not an issue: 50k, or even bigger, should be fine. But 
please test it first. We have discussed raising the default but we’re not quite 
ready to make that change in a major release just yet.

Be aware, though, that if the resolver can’t get answers, it will probably 
SERVFAIL clients and the larger the backlog of clients the longer it will take 
to get around to responding to them, by which time they are likely to have 
timed out and be retrying anyway.

I hope that helps.
Greg

> On 8 Nov 2024, at 10:20, Pedro García Segura <pedr...@gmail.com> wrote:
> 
> Hello,
> 
> Recently we had a Internet outage that lasted for a few hours and quickly 
> filled the recursive clients quota (set at 1000) since most internet-bound 
> recursive queries timed out, and our network is huge.
> 
> This also affected recursive queries to internal authoritative domains, thus 
> interrupting access to critical internal resources which don't have any 
> Internet/SaaS dependencies.
> 
> I'm having a hard time understanding the default recursive max quota being 
> set at 100 by default, since most modern servers now have RAM to spare, and 
> it's a bit scary to think that another Internet outage may happen again and 
> internal critical services may not be able to resolve internal authoritative 
> zones.
> 
> Can anyone give some insight into this issue? Can I just configure a huge 
> number of maximum recursive clientes (say 50k) to "absorb" the intetnet-bound 
> queries that are timing out and be able to respond to client requests for 
> internal authoritative zones?
> 
> I'm probably missing something, so thanks a lot for your understanding!
> 
> Cheers!
> Pedro
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