To access your surfboard cable modem open your web browser and use the IP address of 192.168.100.1. If your router has the same IP address you will have to change your LAN scope to something different such as 192.168.1.1. Once that is done, you should be able to type 100.1 into your browser and it will bring up the Motorola Surfboard modem GUI.
More information on the Motorola Surfboard GUI can be found here: http://www.voipmechanic.com/motorola-surfboard-modem.htm
More information on the Motorola Surfboard GUI can be found here: http://www.voipmechanic.com/motorola-surfboard-modem.htm