Many cable systems make the assumption for the purposes of authentication of the user that there will be only 1 computer in use. When you initially began the service it read the MAC address of the computer you used and stored it in a database.
Now you go out and buy a router because you want to share the internet connection among three computers. The router has a MAC address, but obviously it is not the same one as the computer you first used. Result: you cannot authenticate and the cable system will not allow you internet access. The workaround, built into the router firmware, is to "clone" the MAC address of that first PC. Then when the cable system tries to authenticate it "sees" what appears to be that first machine and is happy as a clam.
Which leads to some obvious questions/problems:
1. Won't it screw up switching if I have two devices with the same MAC address? Answer: No, as one MAC address sits on the public or non-switched WAN side of the router, and the other sits happily on the switched private LAN side.
2. What if I type in the MAC of a different computer than the first one I used to start cable service, or what if I mistype the MAC address in the router? Answer: You will not have cable service.
3. MAC cloning sounds like a kludgy hack, isen't there a better way to do this? Answer: Actually it is an elegant hack. But the best way to handle the problem is to call the cable company, tell them you have a new computer, and give them the MAC address of the router.
In your case MrBreeze the MAC cloning is obviously important, and the best approach would be in the router to put all zeros, i.e. tell the router to display its native MAC address, and then write it down and call the cable company to register that address. While on hold write down the DNS entries that show on the router status page or something like that.
But I would like to ask you to do one other thing for poor computer #3. Under Network Connection, Properties, DNS I want you to put the DNS entries you found from your router. If there are only one or two, thats fine, make them the first and seond entries under DNS. Make the final entry the gateway port of the router, 192.168.1.1. Do an ipconfig release/renew sequence.
The reason for this is that the router provides a mini-DNS proxy server on its Gateway, but I have seen NIC adapters that just would not be happy without a physical DNS server made as the primary DNS entries.