If your using someone elses proxy, you use the proxy's IP as the gateway IP. While some consider Proxies evil to re-route traffic, I use to use Squid for caching frequently visited sites for dial-up user applications for pages to load quickly when visiting a webpage that doesnt change often. I then have a macro that surfs to frequently visited sites as a scheduled task to pre fetch the information to the cache so that when my friend goes to a web page that is part of this pre fetch he gets an almost instant web page load as long as the content hasnt changed between the time of the pre fetch and the time when viewing the page. Now days he has a 3G tether to his PC for fast internet vs dial-up.
