Now that you say that, I have seen places in third party firmware (like dd-wrt) to enter in login info to connect to the ISP, but I've never had an ISP where you've actually had to use that, and I've had 3 different broadband ISPs. The way it's always worked for the ones I've had is you register your modem with the ISP, and then you can connect any router you want to the modem without any special passwords or anything.