Windows 2000, Windows XP, Windows Server 2003, and future Windows Operating Systems added the ability to cache DNS lookup results in the client's cache. This lowers the activity on the LAN and on the Web, but if a failed query is due to incorrect configuration, the client must use ipconfig /flushdns to remove it from the cache once fixed.

NOTE: To see the cache, type ipconfig /displaydns in the CMD.EXE window. You will see a display like:

Windows IP Configuration                                       www.scrubtheweb.com                                       ----------------------------------------                                       Record Name . . . . . : www.scrubtheweb.com                                       Record Type . . . . . : 1                                       Time To Live  . . . . : 2802                                       Data Length . . . . . : 4                                       Section . . . . . . . : Answer                                       A (Host) Record . . . : 66.93.156.37                                       pagead.l.google.com                                       ----------------------------------------                                       Record Name . . . . . : pagead.l.google.com                                       Record Type . . . . . : 1                                       Time To Live  . . . . : 121                                       Data Length . . . . . : 4                                       Section . . . . . . . : Answer                                       A (Host) Record . . . : 64.233.169.104                                       ns02.penton.com                                       ----------------------------------------                                       Record Name . . . . . : ns02.penton.com                                       Record Type . . . . . : 1                                       Time To Live  . . . . : 81145                                       Data Length . . . . . : 4                                       Section . . . . . . . : Answer                                       A (Host) Record . . . : 63.167.165.7                                       .... snip ......
If you wish to avoid caching failed DNS lookup results, you can set the NegativeCacheTime Value Name, a REG_DWORD data type, to 0 at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters using PolicyMakerâ„¢ Registry Extension freeware, or you can include the following in a Startup script:
REG.EXE ADD HKLM\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters /V NegativeCacheTime /T REG_DWORD /F /D 0
NOTE: REG.EXE is built into Windows XP, Windows Server 2003, and later operating systems, or installed from the Windows 2000 Support Tools.