Friday, January 30, 2009

MaxCacheTtl Registry key

Recursive query records are saved by the DNS server. The length of cache time of saved records is determined by the TimeToLive (TTL) field in the record. This registry key determines maximum cache time of records saved by dns server irrespective of TimeToLive (TTL) field in the record. The DNS server deletes records from the cache when MaxCacheTime expires, even if the value of the TTL field in the record is greater than MaxCacheTime.

The registry key is located at "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Parameters"

Key Name:
Type : DWORD
Default : NoKey (Cache for up to one day)
Range : 0x0 | 0x1–0xFFFFFFFF seconds

To change the value the registry key to some cache time say 200 seconds, run the following

reg add "HKLM\SYSTEM\CurrentControlSet\Services\DNS\Parameters" /v MaxCacheTtl /t reg_dword /t 200

Note: 1. The changes to registry key through regedit will be effective only after restarting the DNS server.
2. This registry key doesnot have effect on WINS records saved in the DNS memory cache.

3. This registry key is supported by windows 2ooo, windows 2003 and windows 2008.


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