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Q182781: Client Connections to Multihomed Server Not Load Balanced

Article: Q182781
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
========

You have a number of clients that are using TCP/IP to connect to a multihomed
server that has no IP addresses on the same subnet as the client and the clients
are always connecting to the same address on the server, even though the paths
to more than one of the addresses are equal.

CAUSE
=====

When the client's NetBT layer attempts to resolve the NetBIOS name to an IP
address, it queries the WINS server for the address of a multihomed server and
receives a list of addresses that are always in the same order. NetBT then takes
that list and sorts it, putting addresses on the same subnet (if any) at the
top, followed by addresses in the same network class, and then any remaining
addresses. It then starts at the top of this list and pings the first address to
make sure it is valid. If it does not get a reply, it will go on to the next
address; if it does get a reply, it will use the first address.

The problem is that, within these three categories, the order of addresses is
left unchanged from the list provided by the WINS server. This means that, as
long as the first address in the list is online, it will be the one that is
always used by every client, which does not provide for load balancing.

For additional information, please see the following article in the Microsoft
Knowledge Base:

  ARTICLE-ID: Q161425
  TITLE : WinNT 4.0 SP2 Multi-Homed Computer Connection Enhancement

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


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
Issue type        : kbbug
Solution Type     : kbfix

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