Re: Recommended DNS server for a medium 20-30k users isp

[brent saner via NANOG <nanog () lists nanog org>]

On Thu, Aug 7, 2025, 20:45 DurgaPrasad - DatasoftComnet via NANOG <
nanog () lists nanog org> wrote:

> Hello all,
> Do you have any recommendations for recursive DNS servers for a medium
> sized (20-30k users) ISP.
> We have used powerdns and unbound but sometimes find the caching times a
> bit on upper side. Any suggestions between these two or anything new?
> Also need points on how much we tune the settings
> pros and cons if any.
>
> Thank you /DP

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It's surprising that you didn't get the performance you hoped for out of
PowerDNS. You already tried the suggestions in their tuning guide[0], I'm
assuming?

You may also want to load in entire zones to the hot cache[1].

And there's always horizontal scaling; sometimes you just plain hit limits
on vertical scale.

I haven't tried it yet, but dnsdist[2] should let you do this.
(Or keepalived and/or HAproxy, or... etc. Any loadbalancer that can handle
raw TCP and UDP.)
Dnsdist in particular seems explicitly targeted towards a large set of
untrusted clients with additional optional "safeguarding/consumer
protection" features. Quad9 uses it in some fashion, if I recall correctly.

[0] https://doc.powerdns.com/recursor/performance.html
[1] https://docs.powerdns.com/recursor/lua-config/ztc.html
[2] https://www.dnsdist.org/index.html
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