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

[Saku Ytti via NANOG <nanog () lists nanog org>]

On Fri, 8 Aug 2025 at 12:19, Måns Nilsson via NANOG
<nanog () lists nanog org> wrote:

> my one advice on anycast is to make _certain_ that the routing reflects
> service availability on individual nodes -- i.e a node that can't answer
> queries MUST stop advertising the resolver /128 (or /32 if you have that).

If you do this in a single ASN, where you can guarantee preferences
are honored, then instead of pulling advertisement, deprefer it.

Eventually you will manage to cause an issue, where all advertisements
are falsely pulled.


Same strategy works in any domain where you are testing if something
works, like default route by pinging 8.8.8.8, don't pull, depref.
-- 
  ++ytti
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