DOCUMENT:Q131865  23-JUN-1995  [winnt] 
TITLE   :SMC Elite Ultra NIC Causes UNIX Computers to Disconnect TCP/IP
PRODUCT :Microsoft Windows NT
PROD/VER:3.11 3.50 3.51
OPER/SYS:WINDOWS
KEYWORDS:kbnetwork kb3rdparty kbhw kbbug3.50 kbfix3.50

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The information in this article applies to:

 - Microsoft Windows NT Workstation versions 3.5 and 3.51
 - Microsoft Windows NT Server versions 3.5 and 3.51
 - Microsoft TCP/IP-32 for Windows for Workgroups, versions 3.11, 3.11a,
   and 3.11b
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SYMPTOMS
========

TCP/IP connections between two UNIX computers or between a Microsoft
network computer and UNIX computer are lost.

This happens on a network with both UNIX computers and a computer running a
Microsoft protected mode TCP/IP protocol stack (including TCP/IP-32
versions 3.11, 3.11a, and 3.11b and Windows NT versions 3.5 and 3.51) and
where the Microsoft network computer is using the SMC Elite Ultra network
interface card (NIC).

CAUSE
=====

The SMC Elite Ultra NIC incorrectly passes up ethernet packets addressed to
other computers. This causes the Microsoft TCP/IP protocol stack to send an
ICMP Host Unreachable message back to the source computer. Some UNIX TCP/IP
stacks disconnect when they receive this ICMP packet.

WORKAROUND
==========

To work around the SMC hardware problem, Microsoft has removed the code
from the protected mode TCP/IP stack which sends the ICMP Host Unreachable
message under these circumstances.

Versions of the Windows NT file, TCPIP.SYS, date stamped 6/14/95 or later
incorporate the above workaround.

Versions of the Windows for Workgroups TCP/IP-32 file, VIP.386, date
stamped 7/19/95 or later incorporate the above workaround.

This workaround is also included in the release version of Windows 95.

STATUS
======

Microsoft has confirmed this to be a problem while using Windows NT
versions 3.5 and 3.51 and Windows for Workgroups TCP/IP-32 versions 3.11,
3.11a, and 3.11b. A workaround to this problem is in development, but has
not been regression-tested and may be destabilizing in production
environments. Microsoft does not recommend implementing this workaround at
this time. This workaround is available from Microsoft Product Support
Services as well as electronically by "anonymous" ftp at:

   ftp://ftp.microsoft.com:/bussys/winnt/winnt-unsup-ed/fixes/nt35/icmpfix

   -and-

   ftp://ftp.microsoft.com:/bussys/winnt/winnt-unsup-ed/fixes/nt351/icmpfix

   -and-

   ftp://ftp.microsoft.com:/bussys/clients/wfw/tcpip32-fixes/icmpfix

The Elite Ultra is manufactured by SMC, a vendor independent of Microsoft;
we make no warranty, implied or otherwise, regarding this product's
performance or reliability.

Additional reference words: prodnt 3.11 3.50 3.51 sniper
KBCategory: kbnetwork kb3rdparty kbhw kbbug3.50 kbfix3.50
KBSubCategory: nttcp nthw ntdriver

=============================================================================

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Copyright Microsoft Corporation 1995.