I have a network set up, and recently replaced our two Windows Server 2008 R2 domain controllers with two Windows Server 2012 R2 domain controllers. Both are VMs, each on a different physical machine. Both of my domain controllers have DNS server enabled, and both are configured to use five different external Forwarders (and to use root hints if no forwarders are available).

Since the upgrade, we now experience DNS timeouts twice a day (these timeouts occur on both the dns server itself, and clients. At the moment the pattern seems to be at around 7:30am the dns timeouts happen, and then again at the end of the day. A reboot of the main primary DNS server resolves the issue.

I have no idea why this is happening, and would like to reach out to the community for help!

nslookup with d2 param when everything is working (partial results):


SendRequest(), len 46 HEADER: opcode = QUERY, id = 4, rcode = NOERROR header flags: query, want recursion questions = 1, answers = 0, authority records = 0, additional = 0

QUESTIONS:
    www.bbc.co.uk.electrum.co.uk, type = A, class = IN

------------

Got answer (108 bytes): HEADER: opcode = QUERY, id = 4, rcode = NXDOMAIN header flags: response, want recursion, recursion avail. questions = 1, answers = 0, authority records = 1, additional = 0

QUESTIONS:
    www.bbc.co.uk.electrum.co.uk, type = A, class = IN
AUTHORITY RECORDS:
->  electrum.co.uk
    type = SOA, class = IN, dlen = 50
    ttl = 837 (13 mins 57 secs)
    primary name server = ns0.lumison.net
    responsible mail addr = hostmaster.lumison.net
    serial  = 2013112000
    refresh = 28800 (8 hours)
    retry   = 7200 (2 hours)
    expire  = 604800 (7 days)
    default TTL = 7200 (2 hours)

And again, but this time when it's not working (partial results):

SendRequest(), len 46 HEADER: opcode = QUERY, id = 4, rcode = NOERROR header flags: query, want recursion questions = 1, answers = 0, authority records = 0, additional = 0

QUESTIONS:
    www.bbc.co.uk.electrum.co.uk, type = A, class = IN

DNS request timed out. timeout was 2 seconds. timeout (2 secs) SendRequest failed

Any help is greatly appreciated!

EDIT:

It seems that doing a tracert 8.8.8.8 from the domain controller FIXES the issue, until it happens again 24 hours later.

  • Is the timeout only with forwarded queries or for internal/authoritative queries as well? – TheCleaner Dec 3 '13 at 14:11
  • FROM MAIN DC (DNS) SERVER: - nslookup external failed - Pinging our gateway failed - Pinging External IPs failed - Pinging internal IPs succeeded FROM ANOTHER CLIENT COMPUTER: - nslookup external failed - Pinging our gateway succeeded - Pinging External IPs succeeded - Pinging internal IPs succeeded Also, this morning it started working on it's own without a reboot (and just happened to start workign whilst doing a tracert from the main DC to an external ip). – zikoziko Dec 4 '13 at 9:31

Are you definitely querying www.bbc.co.uk.electrum.co.uk?

It looks like nslookup is appending your own domain name to the end of the query -- this probably won't resolve on anyone's DNS, so is passing up the chain of forwarders (which shows as a timeout for each forwarder it hits).

Try querying www.bbc.co.uk. (note the dot at the end) to avoid the appending behaviour.

  • Ah...good read. I hadn't noticed the doubling up of 2 TLDs there...I would bet you are correct. A nslookup with the debug option would prove this as well. – TheCleaner Dec 4 '13 at 13:52
  • I don't think this is the issue. We have a domain, therefore any lookups need to first check if the resource exists in the domain. And anyway, when everything is working it does these lookups and they work (ie they don't time out). – zikoziko Dec 9 '13 at 9:40

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