Configure WSUS to Use a Proxy Server
If you use a proxy server on your network, use the WSUS console to configure WSUS to use the proxy server. This is necessary in order to synchronize the server with Microsoft Update.
To specify a proxy server for synchronization
On the WSUS console toolbar, click Options, and then click Synchronization Options.
In the Proxy server box, click Use a proxy server when synchronizing, and then enter the server name, and port number (port 80 is the default) of the proxy server in the corresponding boxes.
If you want to connect to the proxy server under specific user credentials, click Use user credentials to connect to the proxy server, and then enter the user name, domain, and password of the user in the corresponding boxes. If you want to enable basic authentication for the user connecting to the proxy server, click Allow basic authentication (password in clear text).
Under Tasks, click Save settings, and then click OK when the confirmation box appears.