The Motorola Surfboard 4100 and 4200 Cable Modem series are common devices provided by cable Internet services. They are easily configurable for use under Linux. For more information about the device not related to Linux configuration, please see the manufacturer's website here.

There are two requirements for using a Motorola Surfboard 4100 and 4200 series USB cable modem (hereafter referred to as a 'Surfboard'). The first is the appropriate networking support for the device in your kernel; note that most base installs of Linux distributions come TCP/IP and ethernet enabled 'out of the box,' so there is probably very little most readers will need to do other than be sure their ethernet card is working. If you know that your ethernet card is supported and working you can move on to Section 2.2, “The Modem Device”. For those who like to compile their own kernels (see the Kernel HOWTO for more information), the following options are required to get the cable modem to work:

Under 'Networking options':

along with ONE of the following:

PPP support is not required per se, as the modem is itself a PPP link.

Note that there are two possible interfaces on the modem to connect your computer. One is through ethernet and is probably the default a cable provider will attempt to use when setting up the Surfboard. The other is to use the USB interface. The former of these is arguably easiest; the only requirements other than the above is that you have an ethernet card installed which is open, i.e. that you can connect to the modem ethernet jack using ordinary 10BaseT/100BaseT ethernet cable. If you are uncertain about anything in the last sentence I recommend you read the Ethernet HOWTO for proper configuration of your ethernet card.

I have used my own 4100 model with each interface, and at least on my system there seems to be little difference in performance using an ethernet card or the USB port. The drawback of the ethernet method is that your network card will be tied up.

First, plug in and turn on the Surfboard. Connect your ethernet card to the Surfboard with 10BaseT/100BaseT cable into the non-USB interface, if this was not already done for you. Be sure the modem isn't on standby mode by checking the LEDs; you should see some dancing green lights to confirm this. The standby button is on the top of the device on most models. Your cable internet provider should be able to tell remotely whether your modem is connected and functioning properly, which is helpful for differentiating between hardware and configuration problems on your end. They will also need the MAC (Media Access Control) hardware address of your modem to allow the device access to their network. If at any time you substitute one modem for another you will need to inform them so the MAC address can be updated and your access to the cable network restored.

Once you connect for the first time, your modem will be assigned an IP address, which may remain the same or change periodically depending on the IP address turnover of your ISP's DHCP server, and how long you remain offline if you disconnect. Should the IP address provided to the modem by your ISP ever have to be released, for whatever reason, you can do this by resetting the device. This involves inserting the tip of a sharp pencil or a pin into the small orifice on the input face. The only time this may be necessary is if you are having trouble with your connection and you are instructed to try this maneuver by your ISP's technical support staff. Only do this if you know what you're doing or are directed to do so by your ISP, as it's generally not a good idea to go around sticking metal objects into the various openings of electrical devices.