Microsoft KB Archive/194892

= Load-Balanced Application Does Not Work Properly Using WLBS =

Article ID: 194892

Article Last Modified on 10/31/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT Load Balancing Service

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This article was previously published under Q194892



SUMMARY
An application that is load balanced does not appear to work correctly when running Windows NT Load Balancing Service (WLBS).


 * All of the application's ports are not being load balanced. Some applications require multiple ports to perform their functions. For example, FTP uses ports 20 and 21. If both ports are not load balanced (usually with one port rule), the application will not work correctly. Check that the applicable port rule covers all ports used by the application and be sure to enable client affinity (single or Class C).
 * The application is not started on all cluster hosts. WLBS does not start or control applications. You should check that the application has been started on every cluster host. If an application fails, you can disable its associated port range using the wlbs disable command.
 * The application should not be load balanced. Applications that update a file on the local cluster host may not work correctly when load balanced because multiple instances of the application may conflict when attempting to update a common file. For example, e-mail, groupware, and database servers often have this problem. Do not load balance an application until its data sharing requirements are thoroughly understood and met.
 * The application is not a TCP/IP service. WLBS load balances applications by distributing incoming client requests among the cluster hosts. If a server application is not structured as a TCP/IP service that receives client requests, it will not benefit from using WLBS, and you will not observe load balancing.
 * Your firewall is proxying client traffic and making it appear as if all connections are originating from the same client IP address. If the load balancing rule is configured with Single affinity, all traffic will be handled by the same cluster host. Turn off address translation (proxying) on the firewall or change affinity from Single to None.

NOTE: You may need Single affinity to provide session support.

Additional query words: WLBS Convoy

Keywords: kbinfo KB194892

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