[chillyjim]

It becomes a question of why do you have separate networks then. The main reason for different networks on a LAN is to breakup broadcast domains and to isolate traffic flow. If you end up putting all of that on one "wire" anyway you might as well use a flat IP space.

You really should split this up into different VLANs from a traffic flow and management standpoint as well as a security standpoint. With just one physical network there is no way to force the traffic to the firewall, I can just send my packets straight to the system I want using it's MAC address and not its IP address.