A Motorola cable modem comes preconfigured with a MAC address that is unique to your device. This MAC address is used to identify your modem as well as communicate with devices such as a router. If your Motorola cable modem fails to work with your router, you may have a communication problem due to a conflicting MAC address. Change the MAC address on your Motorola cable modem to ensure your router can communicate with your modem and Internet Service Provider.
Launch any Web browser and navigate to the Motorola cable modem administrator console. The default address is "http://192.168.100.1." Press "Enter."
Type your username and password and click "Log In."
Click the "Advanced" tab.
Click the "MAC Address Clone" tab.
Type the desired MAC address in the MAC address field.