DNS load balancing: UDP or TCP ?

Josh Kuo josh.kuo at gmail.com
Tue Feb 19 19:00:28 UTC 2019

Agree with Tony on TCP not going to be tried. Have you looked at using
anycast? It is not true load balancing but it allows you to stand up
multiple DNS servers that “shares” a single IP address.

On Wed, Feb 20, 2019 at 12:25 AM Tony Finch <dot at dotat.at> wrote:

> Roberto Carna <robertocarna36 at gmail.com> wrote:
> > Dear, I have to balance two DNS servers for a special reason.
> https://www.powerdns.com/dnsdist.html
> > The DNS clients are a mix of Windows, Cisco and Linux machines, so I
> > think they ask for a FQDN using UDP and after that -if there is no
> > response-, they ask the same FQDN using TCP, and so the load balancing
> > will be succesful.
> No, fallback to TCP relies on receiving a truncated UDP response. You
> never want a DNS client to be waiting around for a response that will
> not arrive.
> Tony.
> --
> f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
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