Cannot connect to SB8200 Router has IP address

The SB8200 should only have 1 device connected to it even though it has 2x ethernet ports. Reason why is most ISP’s only assign a single public ip address to it. Its then on the connected router to assign private ip addresses to devices (simple version). 

So only connect 1 device to the sb8200

I guess I didn’t explain this very well. In order to connect to the modem it has a fixed IP address of 192.168.100.1 but the router takes that address as well.  Ergo I can’t connect to the modem. 

You'd want to contact and ask them why their device is setting up with that address. the modem doesn’t assign that to the router. Modem only devices have few settings and there isn’t anything to modify on them. Its on the router. 

??? I guess I am not getting the point here?  If I connect the Modem to the ISP (in this Case) Cox. It gets the IP address they assigned.  When I connect the modem to the router, the router is not getting a local IP address for the modem. 

The instructions with the modem are to connect to it via the ip address 192.168.100.1 however the router, by design evidently takes that IP address for itself. 

It all works, I just cant connect to the modem?

If the router is not providing a valid IP address, I recommend contacting the router manufacturer for further assistance.

To check the modem, you can connect any device (such as a computer or laptop) via Ethernet cable and try accessing the internet.