Hardware Firewall and cPanel

We would like to keep the software cPanel system different from our firewalls. We currently have M0n0wall installed in a main server and are piping the connections to different cPanel servers depending upon the IP address that is requested.

Here is our problem. cPanel does not respond to requests to a website when that ip address is going through a firewall first to a Class C address range.

How do we fool cPanel into thinking that requesting Class C IP Address X = Requesting Class A IP Address Y?

Thanks.