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Our Windows 2008 R2 SP1 DNS server has a response time of > 3500ms but as low as 1.2ms with a mean of 124ms. I am using OpenDNS for my forwarders. I also enabled 'scavenge stale resource records' and installed the IPv6 disabled hotfix and I'm wondering is slow just because it's Windows? scavenge stale resource records

Fastest vs Mean Response time

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The plus 3 second time may indicate a network or configuration issue. A few things that may be timing out:

  • Dropped packet. The second packet is often sent after a 3 second delay. Tunable on some stacks.
  • Failing primary DNS. DNS stacks will timeout and try the next server after a delay, generally moving to the second server. Cached values will be returned immediately (xx ms).
  • UDP access to DNS blocked, or failing due to packet size.

Try using nslookup with the server specified to test DNS access.

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