New
#31
They shouldn't do it but that's not to say they aren't going to do it :)
The modem is a learning device, it will learn from the start what machine is connected to it during initial setup, this will be logged at the ISP end. This is not to say the modem cannot learn more MAC addresses. People buy new machines so the modem has to know that MAC address has changed and it has to learn this. I have not come across a modem that doesn't have this capability.
Have you spoken to your ISP, resetting the modem would be what they might end up asking you to do anyway.