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How to Disable Client-Side DNS Caching in Windows

Article ID: 245437 - View products that this article applies to.

This article was previously published under Q245437

SUMMARY

Windows 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 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.

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MORE INFORMATION

The actual DNS request is being sent to the local DNS cache. If the entry is listed there, Windows 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

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756

(http://support.microsoft.com/kb/322756/ )

How to back up and restore the registry in Windows

Start Registry Editor (Regedit.exe).
Locate the MaxCacheEntryTtlLimit value under the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters
On the Edit menu, click Modify. Type 1, and then click OK.
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.

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