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Q264632: DLC Session Hangs When Using DLSW

Article: Q264632
Product(s): Microsoft Windows NT
Version(s): 4.0
Operating System(s): 
Keyword(s): kbWinNT400PreSP7Fix
Last Modified: 08-MAY-2002

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The information in this article applies to:

- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Workstation version 4.0 
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SYMPTOMS
========

You may experience session disconnects under heavy network load when you are
using Cisco routers with Data-Link Switching (DLSW) activated.

CAUSE
=====

When an error condition occurs on the network, the stations attempt to
reconnect. When you are using DLSW, the Windows NT Data Link Control (DLC) stack
may enter an invalid state from which it cannot recover. If you are using a
Network Monitor trace, the problem is visible when the client's DLC stack sends
"I" frames although it should be in a disconnected state.

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
  ------------------------------------------------
  07/12/2000  05:06p  102,512  Dlc.sys    Alpha
  07/12/2000  05:08p   55,376  Dlc.sys    Intel



WORKAROUND
==========

If local "acks" (DLC spoofing) are disabled on the routers, this problem does
not occur.

STATUS
======

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

Additional query words:

======================================================================
Keywords          : kbWinNT400PreSP7Fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version           : :4.0
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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