Question regarding cable modem and fresh install

[Nocturnal]

Most times people reformat their computers and once they install Windows, Windows detects a broadband connection. Other times it does not. What causes this? Also when a person switches a computer like say someone has a desktop that is connected to a cable modem and then they switch the ethernet cable to a laptop and the connection doesn't work without having to power cycle the modem. What causes this?

 

[amdskip]

Usually for a cable modem ISP, the computer is registered on their network but it's mac address. If the mac address changes, the new one needs to be registered with the ISP. You can only have one registered in most cases unless you pay for multiple macs thus this is where routers come in to play so you don't have to pay extra.

If formatting a computer without changing the nic, it will work sometimes without doing anything or running the networking wizard.

 

[Nocturnal]

So basically all NICs have mac addresses and the cable modem basically assigns itself to that MAC or not assigns but associates itself with that MAC address... and if it doesn't see that MAC address it thinks something may be wrong?

 

[amdskip]

If the mac's match, you are then authorized to use their network/service.