FVS318N refuses to connect to comcast modem

The modem from the cable internet provider has 4 ports on it which I listed before, each of those ports I have something plugged into it. I have 2 stand-alone machines that each have an IP address assigned to them (one of the 5 static IP addresses that is provided by the internet provider Comcast) and they work fine. The other 2 ports I have firewall devices plugged in and have been attempting to assign them static IP addresses also but I cannot get either of the devices to see the modem even though they are directly plugged in to one of the ports. As I said, the FVS318n is brand new and has not been configured to block anything. Just plugging it in and setting an IP address should work but it refuses. I have tried spoofing the MAC address of the device to be the same MAC address of my laptop which will work when I pulg it in direct to the modem and assign it the smae IP address that I'm trying to use. I've talked to Comcast and Netgear several times and NO ONE has any solutions to add. Just hoping maybe someone has a glimmer of hope for me.