DOCUMENT:Q155883  09-AUG-2001  [winnt]
TITLE   :NT 4.0 Breaks SNA Server 2.x Server Communication Over IP
PRODUCT :Microsoft Windows NT
PROD/VER:winnt:
OPER/SYS:
KEYWORDS:kbnetwork

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The information in this article applies to:

 - Microsoft Windows NT Server 
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SYMPTOMS
========

After you upgrade from Windows NT 3.51 to Windows NT 4.0, SNA Server Admin is no
longer able to locate the primary SNA Server 2.1/2.11 configuration server. This
problem will occur if the SNA Server "server" computers are separated by TCP/IP
routers and no LMHOSTS files are being used to define the Windows NT domain
controllers where the SNA Servers are running.

When you start SNA Server Admin on a Backup SNA Server, the following error will
be displayed:

   The Primary SNA Server for the domain is not active.
   OK to attempt to open to a Backup SNA Server in read only mode?

For more information on troubleshooting SNA Server 2.1 or 2.11 communication
across TCP/IP routers, see the following Microsoft Knowledge Base article:

   ARTICLE-ID: Q148969
   TITLE: Troubleshooting SNA Server Communication Over an IP Router

NOTE: Microsoft SNA Server 3.0 (to be released Fall 1996) does not rely on this
Windows NT mechanism for server-to-server communication across TCP/IP routers.
So, this issue is not relevant if SNA Server 3.0 is being used.

CAUSE
=====

Optimizations made to Netbt.sys under Windows NT 4.0 have introduced a problem
with SNA Server 2.x inter-server communication over TCP/IP routers.

RESOLUTION
==========

Customers can work around the problem by adding an LMHOSTS file on the Windows
NT 4.0 domain controllers where SNA Server is running and adding an entry for
each SNA Server as follows:

   <ipaddress>   <computername>  #PRE #DOM:<winntdomainname>

For example:

   123.123.10.10   SNASERVER1  #PRE  #DOM:NTDOMAIN
   123.105.15.149  SNASERVER2  #PRE  #DOM:NTDOMAIN
   199.199.20.5    SNASALES    #PRE  #DOM:NTDOMAIN

An entry for each domain controller where SNA Server is running is required.

A Windows NT 4.0 fix to this problem is also available from Microsoft which does
not require the above LMHOSTS entries (in other words, in WINS-only
configurations).

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT 4.0. This problem was
corrected in the latest Microsoft Windows NT 4.0 U.S. Service Pack. For
information on obtaining the service pack, query on the following word in the
Microsoft Knowledge Base (without the spaces):

   S E R V P A C K


Additional query words:

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Keywords          : kbnetwork 
Technology        : kbWinNTsearch kbWinNTSsearch
Version           : winnt:
Issue type        : kbbug

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