NXDOMAIN but still get it...

[Darcy Kevin (FCA)]

nslookup sucks.

What’s most likely happening is:

·         On your initial query, some sort of transient error is occurring while trying to resolve centos.mirror.iweb.ca, e.g. a timeout, a misconfigured server returning SERVFAIL, a delegated server not being authoritative, etc.

·         nslookup fails that query, then, behind the scenes (and unbeknownst to you) it starts searchlisting, e.g. looking up centos.mirror.iweb.ca.example.com. This results, as one might expect, in an NXDOMAIN

·         nslookup (mis)reports NXDOMAIN as the result of the overall lookup

You can turn on “-debug” to nslookup to see if this is what’s really happening.

Or, dump nslookup altogether and use a real DNS troubleshooting tool like “dig”.

                                                                                                                                                - Kevin



From: bind-users [mailto:bind-users-bounces at lists.isc.org] On Behalf Of Bernard Fay
Sent: Wednesday, August 03, 2016 3:32 PM
To: bind-users at lists.isc.org
Subject: NXDOMAIN but still get it...

[ ~]# nslookup centos.mirror.iweb.ca<http://centos.mirror.iweb.ca>
Server:        172.21.241.18
Address:    172.21.241.18#53

** server can't find centos.mirror.iweb.ca<http://centos.mirror.iweb.ca>: NXDOMAIN



But ...



[ ~]$ nslookup iweb.ca<http://iweb.ca>
Server:        172.21.241.18
Address:    172.21.241.18#53

Non-authoritative answer:
Name:    iweb.ca<http://iweb.ca>
Address: 174.142.1.18

[ ~]$ nslookup mirror.iweb.ca<http://mirror.iweb.ca>
Server:        172.21.241.18
Address:    172.21.241.18#53

Non-authoritative answer:
Name:    mirror.iweb.ca<http://mirror.iweb.ca>
Address: 192.175.120.177

[ ~]$ nslookup centos.mirror.iweb.ca<http://centos.mirror.iweb.ca>
Server:        172.21.241.18
Address:    172.21.241.18#53

Non-authoritative answer:
Name:    centos.mirror.iweb.ca<http://centos.mirror.iweb.ca>
Address: 192.175.120.169


What am I missing?  There is definitely something I do not understand.

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