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We are experiencing an odd situation, our DNS/domain controllers keep losing there ability to connect to the root hint servers. This lasts for about 5 minutes and happens a few time everyday.

We have hopped on the DNS server while this is happening and have opened a command prompt and were able to successfully ping the root hint servers manually from the DNS servers so we know if is not a internet connectivity issue.

We ran a dcdiag during the event and saw that the DNS servers were able to connect to each other but they could not connect to the root hint servers.

        DNS server: 8.8.4.4 (<name unavailable>)

           9 test failure on this DNS server

           PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 8.8.4.4               [Error details: 1460 (Type: Win32 - Description: This operation returned because the timeout period expired.)]

        DNS server: 8.8.8.8 (<name unavailable>)

           9 test failure on this DNS server

           PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 8.8.8.8               [Error details: 1460 (Type: Win32 - Description: This operation returned because the timeout period expired.)]

        DNS server: 192.112.36.4 (g.root-servers.net.)

           8 test failure on this DNS server

           PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 192.112.36.4               [Error details: 1460 (Type: Win32 - Description: This operation returned because the timeout period expired.)]

        DNS server: 192.203.230.10 (e.root-servers.net.)

           8 test failure on this DNS server

           PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 192.203.230.10               [Error details: 1460 (Type: Win32 - Description: This operation returned because the timeout period expired.)]

        DNS server: 192.228.79.201 (b.root-servers.net.)

           8 test failure on this DNS server

When this is happening we lose the ability to resolve FQDNs

All help would be appreciated.

rahrahruby
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  • What error is generated ? as I wonder if its more a warning than a fail – yagmoth555 Oct 05 '17 at 20:21
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    Thanks for the reply, unfortunately there is no specific error message generated. When this is happening we lose the ability to resolve FQDNs. I have updated the initial question to include the dcdiag failures we are seeing. – rahrahruby Oct 05 '17 at 20:31
  • Why are your errors related to doing PTR look ups for 127.0.0.1? That's just weird. Also these warnings don't show a failure with root hints. They show a failure to query ANY dns server. Your first two attempts are for Google DNS servers. Then it fails over to root hints and fails more. Either your internet is going down or something is blocking the DNS queries on your network. Have you tried to do an nslookup to some other DNS server, like your ISP's, when this happens? – Appleoddity Oct 06 '17 at 04:11
  • Also pinging the server is not a good test. Use nslookup to perform real DNS queries. It could be a network load issue. DNS uses UDP, UDP will be dropped under load. Although it shouldn't be this consistently dropped. Do you have any firewall / filter on the network? That's where I would be looking. I'd also be prepared to plug directly in to the WAN connection and test when this happens. – Appleoddity Oct 06 '17 at 04:15
  • I did nslookups on the root servers while it was happening and was able to resolve them. – rahrahruby Oct 09 '17 at 15:42

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