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Q187709: Domain Name Resolver Caches Responses

Article: Q187709
Product(s): Microsoft Windows NT
Version(s): WinNT:4.0
Operating System(s): 
Keyword(s): kbWinNT400sp4fix
Last Modified: 09-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Workstation version 4.0 
- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Server version 4.0, Terminal Server Edition 
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SYMPTOMS
========

When a Windows Sockets application uses DNS to resolve a hostname to an IP
address by means of the gethostbyname API, the Domain Name Resolver (DNR) on a
computer running Windows NT 4.0 caches the response for the TTL (Time to Live)
specified in the response on a per-process basis. This means that if there is a
change in the IP address of the host computer, the client application continues
to try connecting to the old address. It also means that the same IP address
will be used each time, until the TTL expires, if the response contains multiple
IP addresses.

CAUSE
=====

Winsock2 support was introduced in Windows NT 4.0. Previous versions of Windows
NT supported a MaxHostentCacheSize registry value, which you could set to zero
to disable caching. Support for this parameter was not included in Winsock2.

RESOLUTION
==========

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or
Windows NT Server 4.0, Terminal Server Edition. For additional information,
please see the following article in the Microsoft Knowledge Base:

  Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack


Support for the MaxHostentCacheSize registry value has been added to Winsock2.
The registry value controls the number of cache entries that are available to
the process. If you set the value to zero, no caching will be done.

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\ServiceProvider
\MaxHostentCacheSize

NOTE: The above link is one path; it has been wrapped for readability.

Value type: REG_DWORD
Default value: 10

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT 4.0 and Windows NT
Server 4.0, Terminal Server Edition. This problem was first corrected in Windows
NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition
Service Pack 4.

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Keywords          : kbWinNT400sp4fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch
Version           : WinNT:4.0
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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