I have a network with 2 default gateways (i.e. A, B). A is behind a firewall, while B is directly connected.
I set DHCP for all domain computers to have Default Gateway for A. The firewall is a proxy server (Microsoft TMG). If users doesn't set the proxy (A) in Internet Options, connection is automatically redirected to gateway B and simply access the internet.
How can I prevent this from happening in which users who did not input the proxy should not access the internet?