Hi
In your setup, the nic not connected to your router, would be your internal network, normally connected to some kind of switch, and your MD's will be connected to to that switch, which will have fully access.
You would need to build your MD's etc, ie, connect a computer, not as powerful as the main machine (core/hybrid), power on and the magic happens, once all the drivers are supported for that computer.
You would only need 2 Ethernet cards, unless you have something fancy planned, one for the external, goes to your cable router and one internal, goes to a switch or your wireless router(with DHCP disabled) or Access Point