<div dir="ltr">I am thinking this list is not appropriate for some of my questions... Could someone suggest a better one, maybe as active and rich, as this one, but more appropriate for general DNS discussions?<div><br></div>
<div>Thanks a lot,</div><div>Mohamed.</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sun, Jul 6, 2014 at 2:02 PM, Mohamed Lrhazi <span dir="ltr"><<a href="mailto:ml623@georgetown.edu" target="_blank">ml623@georgetown.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">We had a little mail outage which turned out to be caused by one of our caching DNS servers returning the bellow incomplete reply.<div>
<br></div><div>Clearing the cache on the problematic server fixed the issue.... </div>
<div><br></div><div>Am thinking it is now impossible for me to find the root cause in this instance... but wondering if you guys could hint at what could cause such a problem... bugs in the DNS servers involved? temporary misconfig at Google's servers? network issue?</div>
<div><br></div><div>The setup is a bit convoluted:</div><div><br></div><div>cache server --> resolver cache server --> Internet</div><div><br></div><div>The fix was clearing at the first server. so I am guessing at some point the resolver gave the incomplete answer.</div>
<div><br></div><div>Thanks a lot,</div><div>Mohamed.</div><div><br></div><div><div>➜ ~ dig <a href="http://mail.google.com" target="_blank">mail.google.com</a> @<a href="http://141.161.100.201" target="_blank">141.161.100.201</a></div>
<div><br></div><div>
; <<>> DiG 9.9.5-3-Ubuntu <<>> <a href="http://mail.google.com" target="_blank">mail.google.com</a> @<a href="http://141.161.100.201" target="_blank">141.161.100.201</a></div><div>;; global options: +cmd</div>
<div>;; Got answer:</div>
<div>;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20414</div><div>;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 5</div><div><br></div><div>;; OPT PSEUDOSECTION:</div><div>; EDNS: version: 0, flags:; udp: 4096</div>
<div>;; QUESTION SECTION:</div><div>;<a href="http://mail.google.com" target="_blank">mail.google.com</a>.<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>A</div><div><br></div><div>
;; ANSWER SECTION:</div>
<div><a href="http://mail.google.com" target="_blank">mail.google.com</a>.<span style="white-space:pre-wrap"> </span>10213<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>CNAME<span style="white-space:pre-wrap"> </span><a href="http://googlemail.l.google.com" target="_blank">googlemail.l.google.com</a>.</div>
<div><br></div><div>;; AUTHORITY SECTION:</div><div><a href="http://google.com" target="_blank">google.com</a>.<span style="white-space:pre-wrap"> </span>96485<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>NS<span style="white-space:pre-wrap"> </span><a href="http://ns2.google.com" target="_blank">ns2.google.com</a>.</div>
<div><a href="http://google.com" target="_blank">google.com</a>.<span style="white-space:pre-wrap"> </span>96485<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>NS<span style="white-space:pre-wrap"> </span><a href="http://ns3.google.com" target="_blank">ns3.google.com</a>.</div>
<div><a href="http://google.com" target="_blank">google.com</a>.<span style="white-space:pre-wrap"> </span>96485<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>NS<span style="white-space:pre-wrap"> </span><a href="http://ns4.google.com" target="_blank">ns4.google.com</a>.</div>
<div><a href="http://google.com" target="_blank">google.com</a>.<span style="white-space:pre-wrap"> </span>96485<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>NS<span style="white-space:pre-wrap"> </span><a href="http://ns1.google.com" target="_blank">ns1.google.com</a>.</div>
<div><br></div><div>;; ADDITIONAL SECTION:</div><div><a href="http://ns3.google.com" target="_blank">ns3.google.com</a>.<span style="white-space:pre-wrap"> </span>108462<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>A<span style="white-space:pre-wrap"> </span><a href="tel:216.239.36.10" value="+12162393610" target="_blank">216.239.36.10</a></div>
<div><a href="http://ns4.google.com" target="_blank">ns4.google.com</a>.<span style="white-space:pre-wrap"> </span>108462<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>A<span style="white-space:pre-wrap"> </span><a href="tel:216.239.38.10" value="+12162393810" target="_blank">216.239.38.10</a></div>
<div><a href="http://ns1.google.com" target="_blank">ns1.google.com</a>.<span style="white-space:pre-wrap"> </span>108462<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>A<span style="white-space:pre-wrap"> </span><a href="tel:216.239.32.10" value="+12162393210" target="_blank">216.239.32.10</a></div>
<div><a href="http://ns2.google.com" target="_blank">ns2.google.com</a>.<span style="white-space:pre-wrap"> </span>108462<span style="white-space:pre-wrap"> </span>IN<span style="white-space:pre-wrap"> </span>A<span style="white-space:pre-wrap"> </span><a href="tel:216.239.34.10" value="+12162393410" target="_blank">216.239.34.10</a></div>
<div><br></div><div>;; Query time: 22 msec</div><div>;; SERVER: 141.161.100.201#53(141.161.100.201)</div><div>;; WHEN: Sun Jul 06 12:42:09 EDT 2014</div><div>;; MSG SIZE rcvd: 207</div></div><div><br></div><div><br></div>
</div>
</blockquote></div><br></div>