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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">nslookup sucks.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">What’s most likely happening is:<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:Symbol;color:black"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">        
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">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.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:Symbol;color:black"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">        
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">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<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:Symbol;color:black"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">        
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">nslookup (mis)reports NXDOMAIN as the result of the overall lookup<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">You can turn on “-debug” to nslookup to see if this is what’s really happening.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">Or, dump nslookup altogether and use a real DNS troubleshooting tool like “dig”.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">                                                                                                                                                - Kevin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> bind-users [mailto:bind-users-bounces@lists.isc.org]
<b>On Behalf Of </b>Bernard Fay<br>
<b>Sent:</b> Wednesday, August 03, 2016 3:32 PM<br>
<b>To:</b> bind-users@lists.isc.org<br>
<b>Subject:</b> NXDOMAIN but still get it...<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-family:"Courier New"">[ ~]#
<b>nslookup <a href="http://centos.mirror.iweb.ca">centos.mirror.iweb.ca</a></b><br>
Server:        172.21.241.18<br>
Address:    172.21.241.18#53<br>
<br>
** server can't find <a href="http://centos.mirror.iweb.ca">centos.mirror.iweb.ca</a>: NXDOMAIN<br>
<br>
<br>
<br>
But ...<br>
<br>
<br>
<br>
[ ~]$ <b>nslookup <a href="http://iweb.ca">iweb.ca</a></b><br>
Server:        172.21.241.18<br>
Address:    172.21.241.18#53<br>
<br>
Non-authoritative answer:<br>
Name:    <a href="http://iweb.ca">iweb.ca</a><br>
Address: 174.142.1.18<br>
<br>
[ ~]$ <b>nslookup <a href="http://mirror.iweb.ca">mirror.iweb.ca</a></b><br>
Server:        172.21.241.18<br>
Address:    172.21.241.18#53<br>
<br>
Non-authoritative answer:<br>
Name:    <a href="http://mirror.iweb.ca">mirror.iweb.ca</a><br>
Address: 192.175.120.177<br>
<br>
[ ~]$ <b>nslookup <a href="http://centos.mirror.iweb.ca">centos.mirror.iweb.ca</a></b><br>
Server:        172.21.241.18<br>
Address:    172.21.241.18#53<br>
<br>
Non-authoritative answer:<br>
Name:    <a href="http://centos.mirror.iweb.ca">centos.mirror.iweb.ca</a><br>
Address: 192.175.120.169</span><br>
<br>
<br>
<o:p></o:p></p>
</div>
<p class="MsoNormal" style="margin-bottom:12.0pt">What am I missing?  There is definitely something I do not understand.<br>
<br>
<o:p></o:p></p>
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