So, what you want is to stop traffic going to ports 80 & 443 (http & https) and redirect it to a proxy software ( Squid ). You redirect the traffic with an IP Filter software, available on almost every modern distro, and setting a rule for the redirection. (Search for ipchains, ipfilter & netfilter docs. - Ipchains is older.). With the ipfilter you also stop the rest of the traffic. That's how a firewall works. You'll have to deal with your distro's firewall graphic interface.
For that to take effect, youˇll have to set the server with the IP filter and proxy software as default gateway on the clients.
Last edited by pablob; 03-27-2006 at 03:19 PM.