Access An Cable Modem Through A Router

I have a stand-alone router for my home network. It's plugged into a cable modem set to "Bridge Mode" so they don't fight with each other.

I can access the router's control panel at:

http://192.168.1.1

I can also hit the cable modem's control panel at:

http://192.168.100.1

Those specific addresses will vary depending on which brand of hardware you have, but it should be possible to get to the cable modem through the router in most cases.