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Cable Modem Basics



Ok I'll leave out as much jargon as possible.


A cable modem is identified by the cable company by its Mac address which can usually be found on the underneath of the modem on a sticker with bar codes. This Mac is known as the HFC (Hybrid Fiber Coax) Mac Address. How it works is by using a method know as handshaking, When you boot your modem (Switch it on), the modem will perform some tasks. Firstly the modem will send out a signal saying, "Hey I'm Mac address 00.11.22.AA.BB.CC" (Or whatever the Mac address is). The cable co. then check the Mac address against there data base the Mac address must be known by the cable co. or the modem will not be able to synchronize with the cable co network.


Once the Mac is recognized by the cable co. it will then be assigned a config file. Now a config file is what determines the speed the modem will run at so the config you will be looking to use is the one with the fastest speeds available. So basically the modem says hello I'm Mac Address whatever, the cable co then say yes we know who you are, and this what speed we want you to run at, once all this has been done, you get assigned an IP address and away you go.


Cloning works by copying the Mac address of a modem that is legitimately paid for by a subscriber. This will allow you to receive the same level of service as the paying customer. Now here's the catch, you are able to sniff out Mac address' from any PC that is connected to a cable modem with a valid IP address, but the Mac address' you sniff out will be of no use to you. The cable companies divide their networks into gateways, if two identical Macs appear on the same gateway it'll cause a conflict as the cable co. will not know which modem to assign an IP to, so the two modems will go into a reboot loop where both modems continually reboot each other, giving you very little, if any internet access. Another detail which is very important when buying a modem is it's DOCSIS (Data over cable service interface specification) standard. There are 2 DOCSIS standards "International" & "European". Pure NTL & TW use International DOCSIS whereas EXCW areas use European DOCSIS.


If you live in an I DOCSIS area you will need one of the following:

Ambit 200

Motorola SB4100i, SB4200i or SB5100i


If you live in an E DOCSIS area you will need one of the following:

Ambit 200

Motorola SB4100e, SB4200e or SB5100e


The Ambit 200 will work in either of the areas as it is capable of both DOCSIS standards.