How to Disable Client-Side DNS Caching in Windows 2000

ID: Q245437

The information in this article applies to:
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Datacenter Server
  • Microsoft Windows 2000 Professional
  • Microsoft Windows 2000 Server
IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

SUMMARY

Windows 2000 contains a client-side Domain Name System (DNS) cache. The client-side DNS caching may generate a false impression that DNS "round robin" is not taking place from the DNS server to the Windows 2000 client. Pinging the same A-record domain name may result in the client using the same IP address. This behavior is different from previous Microsoft operating systems.

NOTE: This article refers to the client portion of DNS. Do not use this information for making changes to DNS servers.


MORE INFORMATION

The actual DNS request is being sent to the local DNS cache. If the entry is listed there, Windows 2000 uses the entry and does not make the request to the DNS server. After the entry has timed out (based on its Time to Live, or TTL value), it is cleared from the local DNS cache. The next attempt sends the request to the DNS server.

To view the DNS cache, type ipconfig /displaydns at a command prompt.

To delete the entries in the DNS cache, type ipconfig /flushdns at a command prompt.

To Disable Client-Side DNS Caching

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

  1. Start Registry Editor (Regedit.exe).


  2. Locate the MaxCacheEntryTtlLimit value under the following registry key:


    3. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters
  3. On the Edit menu, click Modify. Type 1, and then click OK.


  4. Quit Registry Editor.


Note that this setting does not really disable the client-side DNS cache. Instead, it lowers the Maximum TTL value within the client's DNS cache to one second. This gives the appearance that the client-side DNS cache has been disabled. Each sequential ping results in a DNS query to the DNS server.

Additional query words:

Keywords : kbenv
Version : WINDOWS:2000
Platform : WINDOWS
Issue type : kbhowto


Last Reviewed: January 3, 2000
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