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Q273027: Gethostbyname() May Return Wrong IP Address

Article: Q273027
Product(s): Microsoft Windows NT
Version(s): 4.0,4.0 SP6a
Operating System(s): 
Keyword(s): kbWinNT400PreSP7Fix
Last Modified: 11-JUN-2002

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The information in this article applies to:

- Microsoft Windows NT Workstation versions 4.0, 4.0 SP6a 
- Microsoft Windows NT Server versions 4.0, 4.0 SP6a 
- Microsoft Windows NT Server, Enterprise Edition versions 4.0, 4.0 SP6a 
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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

When a client computer that is running Windows NT, Microsoft Windows 95, or
Microsoft Windows 98 disconnects and then reconnects by using Remote Access
Service (RAS) and receives a new IP address from the RAS server, the new IP
address is not discovered by a Windows NT 4.0-based server for a variable time
interval (usually a few minutes). This problem was initially noted in a
Microsoft Message Queue (MSMQ) environment, in which the reconnected MSMQ
clients were not discovered by the MSMQ server for a variable time interval.

CAUSE
=====

This problem is caused by the NetBIOS Name Cache management (Netbt.sys) on the
Windows NT 4.0-based server. The lifetime of an entry in the NetBIOS Name cache
is determined by this registry value :

  HKLM\System\CCS\Services\Netbt\Parametes\CacheTimeout

The default value is 600,000 milliseconds (10 minutes).

When a NetBIOS cache entry (such as name00) is used, its remaining lifetime is
reinitialized for a new (CacheTimeout + 1 minute) interval. Therefore, if a ping
name command is issued at a regular time interval that is shorter than
(CacheTimeout +1 minute), the NetBIOS cache entry is revalidated each time; the
new IP address is never discovered (by WINS resolution).

RESOLUTION
==========

A supported fix is now available from Microsoft, but it is only intended to
correct the problem described in this article and should be applied only to
systems experiencing this specific problem. This fix may receive additional
testing at a later time, to further ensure product quality. Therefore, if you
are not severely affected by this problem, Microsoft recommends that you wait
for the next Windows NT 4.0 service pack that contains this fix.

To resolve this problem immediately, contact Microsoft Product Support Services
to obtain the fix. For a complete list of Microsoft Product Support Services
phone numbers and information about support costs, please go to the following
address on the World Wide Web:

  http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

NOTE: In special cases, charges that are normally incurred for support calls may
be canceled, if a Microsoft Support Professional determines that a specific
update will resolve your problem. Normal support costs will apply to additional
support questions and issues that do not qualify for the specific update in
question.

The English version of this fix should have the following file attributes or
later:

  Date        Time    Size     File name  Platform
  ------------------------------------------------
  10/16/2000  07:24p  124,656  Netbt.sys  Intel
  10/16/2000  07:22p  224,912  Netbt.sys  Alpha



STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products that are
listed at the beginning of this article.

MORE INFORMATION
================

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

The MSMQ server periodically accesses all the MSMQ clients by using the
gethostbyname function to discover the new IP address. You can reduce the
discovery latency to two minutes by using the following settings:

- HKLM\System\CCS\Services\Netbt\Parameters\CacheTimeout = 60000 (60 seconds),
  type REG_DWORD in milliseconds

- HKLM\System\CCS\Services\Tcpip\ServiceProvider\MaxHostentCacheSize = 0
  (mandatory, disables the DNS host cache), type REG_DWORD

- HKLM\Software\Microsoft\MSMQ\Parameters\WaitTime = 30000 (30 seconds), type
  REG_DWORD, in milliseconds

Additional query words: waittime

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Keywords          : kbWinNT400PreSP7Fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400sp6 kbWinNTS400search kbWinNTS400 kbWinNTSEnt400SP6a kbWinNTW400SP6a
Version           : :4.0,4.0 SP6a
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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