Microsoft KB Archive/308596

= Network Load Balancing May Reset Clients After a Cluster Is Rebalanced =

PSS ID Number: 308596

Article Last Modified on 5/28/2003

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The information in this article applies to:


 * Microsoft Windows 2000 Advanced Server SP1
 * Microsoft Windows 2000 Advanced Server SP2
 * Microsoft Windows 2000 Server SP1
 * Microsoft Windows 2000 Server SP2

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This article was previously published under Q308596



SYMPTOMS
Network Load Balancing may reset TCP sessions when two or more Network Load Balancing hosts claim ownership of the same TCP connection. This problem can occur after a cluster is rebalanced and an active client Internet protocol (IP) or port is reused in an incoming TCP connection. After a client computer is reset by the server, the reset procedure cleans up the bad state and a subsequent connection using the same IP or port is successful.



CAUSE
If Network Load Balancing is set for Single Affinity, and if the Network Load Balancing network adapter has a metric of 2, traffic flows in to the Network Load Balancing network adapter and out of the dedicated network adapter. When the outgoing traffic from the Network Load Balancing host uses the non-Network Load Balancing adapter, Network Load Balancing cannot correctly track TCP connections. As of Windows 2000 SP1, Network Load Balancing expects to see two &quot;FIN&quot; packets for a particular connection before it gives up ownership of that connection. If the server's replies are going out on the non-Network Load Balancing network adapter, Network Load Balancing does not see the second FIN packet. This behavior is a problem only when cluster membership changes. When cluster membership changes, several Network Load Balancing servers think they own a particular TCP connection.



RESOLUTION
To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

260910 How to Obtain the Latest Windows 2000 Service Pack

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.   Date         Time    Version         Size       File name ---  07-Nov-2001  11:11   5.0.2195.4606   65,616     Wlbs.sys



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows 2000 Service Pack 3.

Additional query words: NLB WLBS NLBS LOAD BALANCING RESET CONNECTION TCP

Keywords: kbWin2000sp3fix kbprb KB308596

Technology: kbwin2000AdvServ kbwin2000AdvServSearch kbWin2000AdvServSP1 kbWin2000AdvServSP2 kbwin2000Search kbwin2000Serv kbwin2000ServSearch kbwin2000ServSP1 kbwin2000ServSP2 kbWinAdvServSearch

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