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Q306378: SNMP sends traps from last bound IP address on interface

Article: Q306378
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
========

If your computer's network adapter is configured with one or more virtual IP
addresses in addition to its primary IP address, and is also running the SNMP
service, you may see in a network trace that the computer uses the last-bound
virtual IP address as the source IP address in any SNMP trap frames that are
generated by the computer (instead of the adapter's primary IP address). This
can cause connectivity problems if the computer is part of a Windows Load
Balancing Service (WLBS) server cluster.

CAUSE
=====

This issue occurs because SNMP selects the first IP address in the list of IP
addresses that are returned by TCP/IP; this is always a virtual IP address if
one or more virtual IP addresses are configured.

The hotfix that is described in this article corrects this problem so that SNMP
always selects a primary IP address for use as the IP source address in SNMP
traps.

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.

To resolve this problem, contact Microsoft Product Support Services to obtain the
fix. For a complete list of Microsoft Product Support Services phone numbers and
information on 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
  -------------------------------------------------
  17-Sep-2001  11:15  24,848  Snmpapi.dll  Intel

NOTE: Because of file dependencies, this hotfix requires Microsoft Windows NT 4.0
Service Pack 6a (SP6a).



WORKAROUND
==========

To work around this issue, install another network adapter in the computer and
configure it so that it uses only a primary IP address and is the first network
adapter in the TCP/IP binding order. SNMP then selects the unique primary IP
address of this first adapter as the source IP address in its trap frames. The
other network adapter can then be dedicated for use in a WLBS cluster if
required.

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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