Microsoft KB Archive/261957

= Network Load Balancing Temporarily Fails in a Switched Environment =

Article ID: 261957

Article Last Modified on 2/28/2007

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APPLIES TO


 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows NT Load Balancing Service

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This article was previously published under Q261957



SYMPTOMS
When you use Network Load Balancing (NLB) with a Layer 2 switch, load balancing clients may experience a brief, temporary disruption of service when a new NLB server is added to, or an &quot;old&quot; server is removed from the cluster.



CAUSE
During the protocol binding operation, the switch learns the cluster media access control address and binds it with the switch port associated with the new NLB server. Now load balancing traffic is sent only to that server rather than balancing the client traffic across all of the NLB servers. After a short period of time (approximately 5 minutes), the switch releases the cluster media access control address from the specific switch port in question.



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



WORKAROUND
In order for NLB to work correctly with a Layer 2 switch, the cluster media access control address cannot be bound or associated with only one switch port.



STATUS
Microsoft has confirmed that this is a problem in Microsoft Windows 2000.

This problem was first corrected in Windows 2000 Service Pack 1.



MORE INFORMATION
For additional information about NLB, click the article number below to view the article in the Microsoft Knowledge Base:

193602 Configuration Options for WLBS Hosts Connected to a Layer 2 Switches

Keywords: kbbug kbfix kbnetwork kbnlb kbwin2000sp1fix KB261957

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