This article was previously published under Q219285
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This article explains how to load balance traffic to FTP servers using Windows NT Load Balancing Service (WLBS).
FTP servers use TCP port 21 for control connection and TCP port 20 for return data connection from the server. Sometimes, the server indicates to the client to use another port (above 1024) to communicate with it.
To Load Balance FTP, configure the following port rules:
Configure a port rule with a range from 20 to 21, protocol TCP, and Affinity set to either Single or Class C (to ensure that both data and control connections are handled by the same server).
Configure a port rule with a range from 1024 to 65535, protocol TCP, and Affinity set to either Single or Class C.
For additional information about how to configure port rules, please see the following article(s) in the Microsoft Knowledge Base: