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Article ID: 273727 - Last Review: October 26, 2013 - Revision: 5.0

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Your computer may stop responding (hang) when the following conditions are true:
  • The Microsoft IPX/SPX protocol is installed on your computer.
  • Your computer receives the IPX/SPX NMPI port denial of service.
  • You are connected to a network that routes IPX packets.


This problem can occur if your computer receives a denial of service that targets an IPX NetBIOS name management port. This type of denial of service can generate large amounts of network traffic (a network storm) by using the IPX/SPX protocol.

A portion of the IPX/SPX protocol that listens on the NMPI port 551h replies to any requesting network address. The NMPI listener software does not filter the requesting computer's network address correctly, and may reply to a network broadcast address, which causes other IPX NMPI listener programs to also reply. This can generate a large amount of unnecessary network traffic.


A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are 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 about support costs, visit the following Microsoft Web site:;EN-US;CNTACTMS (;EN-US;CNTACTMS)
NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual 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     Version    Size     File name    Operating system
12/08/2000  09:30pm  4.00.958    51,052  Nwlink.vxd   Windows 95
02/01/2001  05:03pm  4.00.956   108,264  Vserver.vxd  Windows 95
12/08/2000  09:36pm  4.00.1117   51,567  Nwlink.vxd   Windows 95 OSR2
01/09/2001  01:40pm  4.00.1114  112,904  Vserver.vxd  Windows 95 OSR2
11/28/2000  08:10pm  4.10.2002   51,546  Nwlink.vxd   Windows 98
01/04/2001  10:30pm  4.10.2002  112,912  Vserver.vxd  Windows 98
11/28/2000  07:38pm  4.10.2226   51,551  Nwlink.vxd   Windows 98 
                                                      Second Edition
01/04/2001  10:32pm  4.10.2225  112,912  Vserver.vxd  Windows 98 
                                                      Second Edition
11/28/2000  11:10pm  4.90.3003   51,535  Nwlink.vxd   Windows Me
01/04/2001  10:06pm  4.90.3002  112,896  Vserver.vxd  Windows Me


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

More information

Because this problem only affects computers that are on networks that route IPX, most users cannot be subjected to this denial of service.

For additional information about Windows 95 hotfixes, click the article number below to view the article in the Microsoft Knowledge Base:
161020  ( ) Implementing Windows 95 Updates
For additional information about Windows 98 and Windows 98 Second Edition hotfixes, click the article number below to view the article in the Microsoft Knowledge Base:
206071  ( ) General Information on Windows 98 and SE Hotfixes
For additional information about Windows ME hotfixes, click the article number below to view the article in the Microsoft Knowledge Base:
295413  ( ) General Information About Windows Millennium Edition Hotfixes
For additional information, see Security Bulletin MS00-073. To do so, visit the following Microsoft Web site: (

Applies to
  • Microsoft Windows 95
kbnosurvey kbarchive kbhotfixserver kbqfe kbbug kbfix kbnetwork KB273727
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