Reduce Windows DNS Service caching on Window

If I understand your situation correctly, it's that you're not satisfied with your DNS server's caching of external records. You might want to experiment with these settings on both your DNS server (because it has its own cache) and the end user workstations. Restart the DNS client service after making registry changes.

Incoming Microsoft Support KB:

Using the Registry to Control the Caching Time

The length of time for which a positive or negative response is cached depends on the values of entries in the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNSCache\Parameters

The TTL for positive responses is the lesser of the following values:

• The number of seconds specified in the query response the resolver received
• The value of the MaxCacheTtl registry setting.

Notes

• The default TTL for positive responses is 86,400 seconds (1 day).
• The TTL for negative responses is the number of seconds specified in the MaxNegativeCacheTtl registry setting.
• The default TTL for negative responses is 900 seconds (15 minutes).

If you do not want negative responses to be cached, set the MaxNegativeCacheTtl registry setting to 0.

To set the caching time on a client computer:

• Start Registry Editor (Regedit.exe).

• Locate and then click the following key in the registry:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters

• On the Edit menu, point to New , click DWORD Value, and then add the following registry values: Value name: MaxCacheTtl

  Data type: REG_DWORD Default value: 86400 seconds Value data: If you lower the Maximum TTL value in the client's DNS cache to 1 second, this gives the appearance that the client-side DNS cache has been disabled.

  Value name: MaxNegativeCacheTtl

  Data type: REG_DWORD Default: 900 seconds Value data: Set the value to 0 if you do not want negative responses to be cached.

• Type the value that you want to use, and then click OK.

• Quit Registry Editor.