DNS resolver reaction to non-reachable authoritative DNS server

Thu Mar 13 07:35:23 UTC 2014

Hello there!

I am trying to troubleshoot a case of DNS failure issue with one of Indian
Govt's domain (nic.in). I can see that 1 out of 4 authoritative DNS server
is IPv6 only. We have quite a few users running IPv4 only setup and hence
1/4 of these DNS servers are non-reachable from the recursor hosted by our
clients.

How is DNS query expected to respond in such case? Will it give SRVFAIL and
terminate immediately (causing DNS resolution failure) OR it will just see
one of the auth DNS as non-reachable and next will proceed with either of
other three thus slowing down but with no failure?

Thanks.

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Anurag Bhatia
anuragbhatia.com

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