Buying a Cable Modem, Part 2 -
Contacting the Cable Internet Operator

After the initial setup of your computer and cable modem, you call your cable Internet operator. In my case, this was Cox@Home  (now Cox High Speed Internet). At this time, the cable operator will get necessary information on your system to validate your new modem, and instruct you on the remainder of the setup process.

The change I expected, and dreaded, was the loss of my static IP address. I'd had this address since early 1999, and I didn't want to change to a dynamically assigned (DHCP) IP address. There are security advantages to a dynamic IP address, though, depending on how the cable ISP has set up their system, but they are more for the ISP than for you the cable modem user.

The very helpful person at Cox's tech support 800 number said that she was surprised to hear I had a static address, since "you're not supposed to have one of those."  I told her that, when I was set up in early 1999, @Home was only using static addresses.  Also, I told her that I used to be able to do a reverse DNS lookup of my IP address and find my computer's name.

I was surprised that the "computer name" also had to change along with going to DHCP.  Cox@Home was configured to use the computer name, and probably the MAC address of the cable modem it's coming through, as part of their process to assign you an IP address dynamically. They have to validate the new cable modem's serial number and MAC address on their system in order for their system to talk to you.  She did not ask about the MAC address of my network card.

Note that your networking adapter, whether a network card or a USB adapter between the cable modem and the computer, has its own MAC address. Cable companies can, and some do,   configure their DHCP servers to require the registered MAC address of the adapter, as additional security against providing unauthorized connections.

Just in case, I made sure that the cable modem saw the same MAC address. This can be done by making sure you plug into the network card you've been using, or, if you use a Linksys cable/dsl router, then you can use the router's option to "clone" the MAC address of the known network card.

During the call, the tech support person disables your old cable modem and enables your new cable modem. I was advised to disconnect the old cable modem, and not to connect the new cable modem for 45-60 minutes. I chose 60. You also turn off your computer (and any interim devices such as Linksys routers, switches and hubs) before the startup process. If you are running a home network, I suggest disconnecting all computers but one until you get the system up and running.

After the 60 minute wait, you plug in the cable modem to the RG59 (cable company) cable, plug in the transformer for the cable modem, and wait for the Power light and the Cable light to light up without blinking. The Cable light will blink at first as it gets its initial configuration information and establishes its connection. After the Power and Cable lights are burning constantly, you power on the computer and any hub/switch/router. At this point, the PC light should come on and stay on.

Cable Modems |  Basics |  Buying, part 1 |  2 |  3 |  4

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