Open all ports to an "additional address"

Hey all,

Say I have a system configured to use one of my additional addresses through masquerading. How would I open up ALL traffic to that system? Will I need to convert the subnet to a DMZ or can I open all ports to this system?

Also, having the system masqueraded to this address, will that avoid any NAT tables from being generated? Or does Astaro still depend on NATing all the traffic?

Thanks!
-Nator