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

[Jay Acuna via NANOG <nanog () lists nanog org>]

On Tue, Aug 12, 2025 at 10:48 AM David Prall via NANOG
<nanog () lists nanog org> wrote:

> Can do a quick DNS lookup via a DNS server, since they shouldn't turn
> that off. But, what happens when they notice the same site doing the
> same lookup(s) every x minutes.

I think they won't notice, because that kind of query volume is orders
of magnitude less than
average usage of 1 internet-connected device.   That is if you are
running 2 or 3 queries
every 3 or 4 minutes.   Meanwhile the average web-surfing user
connects to websites that
easily cause 20+ DNS queries over the span of a couple seconds in
order to load a whole
web page with all its JS frameworks, CSS, and Fonts being
remote-loaded from various domains.

Querying the service on the IP with an actual query is the best test,
but it should be: use
a few common FQDNs on different domains to run the lookup on, and not
just one FQDN.
If any of the lookups succeed, then the resolver is deemed "alive and
working / available".

If you only query one FQDN per resolver, then you might not always be
able to easily
distinguish between a failure of the target authoritative domain you
are querying,
versus a lack of responsiveness by that resolver in general

--
-JA
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