On the WEB PROXY menu, under the Upstream proxy submenu, click Proxies.
Under the Manage upstream proxy section, enter a meaningful Name for the upstream proxy.
Enter the IP address or the Hostname of the upstream proxy, enter the Port number to use on the upstream proxy, and enter a descriptive Comment.
To configure client credential forwarding, click Advanced » and choose a method for Client credential forwarding.
If you selected the Disabled option, enter the Username and Password used. If you selected Username only, you only need to enter the password. If you selected Username and password, you can leave both blank.
Enter a Load balance ratio, for example, if one upstream proxy has the value: 2 and another upstream proxy has the value: 1 and both use the round robin load balancing method, then the proxy with value: 2 receives twice as many web requests as the proxy with value: 1.
To add other upstream proxies, repeat the previous steps.