Setting up gateway on cable modem

[Grepawking]

I'm really confused as to how to setup the gateway on my cable modem on my dual WAN setup.

With my netgear router & seperate cable modem, the setup is DHCP for both.  My modem gets an ip address of 192.168.100.1 and router is 192.168.1.1.

When I connect my Cable WAN port (of the pfsense machine) to the netgear router and do a trace route or pathping, I don't see the cable modem 192.168.100.1 in the route, only a 10.160.1.1 (it shows this in the pfsense diagnostics as well).  I can's connect to the modem with 10.160.1.1 but I can with 192.168.100.1 to see the statistics.

When I am done with this setup I'll remove the netgear router and I don't know what to set as the gateway for this device.  I am setting the internal IP address a 192.168.1.254 (the gateway is now set as 192.168.1.1 and it works with the diagnostics of ping & traceroute).

When I remove the netgear router, what should I set the gateway to?