I need to force my users on my network to use a transparent proxy server outside my network to access websites. I'm not sure if I can do this with DNS, by setting up my own DNS which redirects them to the proxy server. How can I achieve this?
One option is to lock the users to a browser that honors the global proxy setting on a system (such as IE on Windows with GPO that applies proxy), but that also requires that you have total control of all clients on your network.
The other option is to redirect every packet destined for HTTP(80)/HTTPS(443) to a Proxy server with transparent support. There are a ton of options here, and we have no idea what kind of router or firewall you have for the redirect part.
One popular solution is WCCP/WCCP2 against Squid.