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We are a small office with 10 client PCs and one Windows SBS 2011 server acting as Domain Controller and Internet gateway. At random times client computers cannot access Internet hosts in the .co.uk domain (we are based in UK). We never have problems with .com or other domains. This has been for happening for a few months now.

This issue persists until the server is rebooted or the DNS Server is restarted, but will come back later at a random time.

Can anyone suggest a permanent fix for this issue? I have a background in Linux so this was all the information I was able to provide but I can post further configuration details if told what is relevant to the issue.

Any help will be much appreciated.

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According to http://support2.microsoft.com/default.aspx?scid=kb;EN-US;968372, this can happen when DNS name resolution is achieved through root hints:

When name resolution is provided by root hints, Windows Server 2008 DNS and Windows Server 2008 R2 DNS Servers may fail to resolve queries for names in certain top-level domains. When this happens, the problem will continue until the DNS Server cache is cleared or the DNS Server service is restarted. The problem can be seen with domains like .co.uk, .cn, and .br, but is not limited to these domains.

You have two solutions at your disposal:

  1. Configure your DNS Server to use DNS Forwarders instead of root hints
  2. Change the MaxCacheTTL registry value to 2 days or greater

Instructions (found in the linked MSKB article) for implementing solution #2 follow:

  1. Start Registry Editor (regedit.exe)
  2. Locate the registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Parameters
  3. On the Edit menu, click New, click DWORD (32-bit) Value, and then add the following value:

    Value: MaxCacheTTL
    Data Type: DWORD
    Data value: 0x2A300 (172800 seconds in decimal, or 2 days)
    
  4. Click OK.
  5. Quit Registry Editor.
  6. Restart the DNS Server service.

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