[Neil]

Originally Posted by Raistlin

you're getting FAR too hung up on MAC addresses. Ignore them, they're the proverbial red herring.....

Your modem will register itself (or provision itself, whatever) to one MAC address at a time only. At the moment it is provisioned to the MAC address of the router, if you change the setup (ie connect a different router or connect directly to a PC) it will stop working because it is still looking for the MAC address of the router.

That's all that matters.

^^ What he said.