Microsoft KB Archive/297040

= Windows May Hang When Attempting to Establish a TCP Connection to a Nonexistent IP Address =

Article ID: 297040

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition Service Pack 6
 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT 4.0 Service Pack 6a

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This article was previously published under Q297040



SYMPTOMS
A Windows NT 4.0-based server with a recent post-SP6a hotfix, or a Windows NT 4.0 Terminal Server with a recent post-SP6 hotfix, may stop responding (hang) if it attempts to make a TCP connection with an IP address that is nonexistent.

For example, if a Windows NT 4.0-based server with an address of 129.68.72.10 attempts to connect by using Telnet to an address of 129.68.72.40, and that address is either nonexistent or unavailable, the server may hang. This is a &quot;hard&quot; hang with no mouse control and no CTRL+ALT+DELETE functionality available. The server is unresponsive from the console and cannot be pinged on the network.

For this hang to occur, the TCP/IP SynAttackProtect registry value must be set. For additional information about this registry entry, click the article number below to view the article in the Microsoft Knowledge Base:

142641 Internet Server Unavailable Because of Malicious SYN Attacks



CAUSE
Under certain circumstances, the spinlock for the TCP/IP connection table lock is acquired but not released; this causes the server to hang.



RESOLUTION
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:

http://support.microsoft.com/default.aspx?scid=fh;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   Size     File name --  27-Apr-2001  15:54  174,896  Tcpip.sys NOTE: Because of file dependencies, this hotfix requires Microsoft Windows NT 4.0 Service Pack 6a.



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

Additional query words: freeze lock lockup

Keywords: kbhotfixserver kbqfe kbbug kbfix kbqfe KB297040

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