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<p class="MsoNormal"><span style="font-size:11.0pt">Hi All<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">One of the customers of a recursive service we operate has reported issues with their users accessing Office 365. Their internal investigation have indicated that the problem probably lies with resolving outlook.live.com
against our service.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">They have reported that when their local resolvers query that domain, the answer they get back varies. So they are sometimes getting this cname chain:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">;; ANSWER SECTION:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">outlook.live.com. 141 IN CNAME live.ms-acdc.office.com.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">live.ms-acdc.office.com. 1729 IN CNAME outlook.ha.office365.com.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">outlook.ha.office365.com. 41 IN CNAME outlook.ms-acdc.office.com.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">outlook.ms-acdc.office.com. 21 IN CNAME LHR-efz.Ms-acDC.office.com.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">LHR-efz.ms-acdc.office.com. 36 IN CNAME outlook-fs.office.com.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">outlook-fs.office.com. 14 IN CNAME outlook-exo.trafficmanager.net.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">outlook-exo.trafficmanager.net. 28 IN CNAME lhr-mvp.trafficmanager.net.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">lhr-mvp.trafficmanager.net. 35 IN A 52.97.165.146<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">lhr-mvp.trafficmanager.net. 35 IN A 52.97.133.178<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">lhr-mvp.trafficmanager.net. 35 IN A 52.97.146.162<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">lhr-mvp.trafficmanager.net. 35 IN A 52.97.179.226<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">lhr-mvp.trafficmanager.net. 35 IN A 52.97.146.146<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">lhr-mvp.trafficmanager.net. 35 IN A 40.100.174.18<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">lhr-mvp.trafficmanager.net. 35 IN A 40.100.174.210<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">lhr-mvp.trafficmanager.net. 35 IN A 40.100.174.34<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">In the above output, the qname LHR-efz.ms-acdc.office.com (5<sup>th</sup> in the chain) is a CNAME.</span><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB">
</span><span style="font-size:11.0pt">However, sometimes it is an A rrset:</span><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<pre><span style="color:black">;; ANSWER SECTION:<o:p></o:p></span></pre>
<pre><span style="color:black">outlook.live.com. 32 IN CNAME live.ms-acdc.office.com.<o:p></o:p></span></pre>
<pre><span style="color:black">live.ms-acdc.office.com. 1727 IN CNAME outlook.ha.office365.com.<o:p></o:p></span></pre>
<pre><span style="color:black">outlook.ha.office365.com. 39 IN CNAME outlook.ms-acdc.office.com.<o:p></o:p></span></pre>
<pre><span style="color:black">outlook.ms-acdc.office.com. 19 IN CNAME LHR-efz.ms-acdc.office.com.<o:p></o:p></span></pre>
<pre><span style="color:black">LHR-efz.ms-acdc.office.com. 1 IN A 52.97.146.162<o:p></o:p></span></pre>
<pre><span style="color:black">LHR-efz.ms-acdc.office.com. 1 IN A 52.97.129.66<o:p></o:p></span></pre>
<pre><span style="color:black">LHR-efz.ms-acdc.office.com. 1 IN A 40.100.174.226<o:p></o:p></span></pre>
<pre><span style="color:black">LHR-efz.ms-acdc.office.com. 1 IN A 52.97.146.194<o:p></o:p></span></pre>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">It’s not unusual for a GSLB to reply with different IPs every time, but I have not seen it before where you sometimes get a CNAME and sometimes A/AAAA. I’m not totally sure why this would be problematic, but
one theory that we are tossing around is that the customer’s caching resolvers are attempting to prefetch the LHR-efz.ms-acdc.office.com record, receiving a NODATA response and therefore responding to the client with NXDOMAIN. I am wondering what people’s
thoughts are on whether this theory has merit?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I was previously able to replicate the issue up until an hour or two ago, now it is responding consistently with an A rrset, so it’s possible that it has gone away.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:11.0pt;color:gray;mso-fareast-language:EN-GB">Paul Harris<br>
</span></b><span style="font-size:11.0pt;color:gray;mso-fareast-language:EN-GB">Senior DNS and Network Engineer<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:black;mso-fareast-language:EN-GB"><img width="112" height="30" style="width:1.1666in;height:.3125in" id="Picture_x0020_1" src="cid:image001.png@01D6AD2E.79536E20" alt="Nominet"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;color:gray;mso-fareast-language:EN-GB">DD: +44 (0)1865 981759 E: </span><span style="font-size:11.0pt;color:black;mso-fareast-language:EN-GB"><a href="mailto:paul.harris@nominet.uk"><span style="color:#0563C1">paul.harris@nominet.uk</span></a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;color:gray;mso-fareast-language:EN-GB">Minerva House, Edmund Halley Road, Oxford Science Park, Oxford, OX4 4DQ, United Kingdom</span><span style="font-size:11.0pt;color:black;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
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