Is it possible to reconfigure a cable modem to work with DSL?

I’m going to say that this is impossible. They have totally different connections and use different protocols.

Usually your ISP will give you a new, compatible router when you switch to their service.

Even before you get to the protocol incompatibility, how would you hook it up? Would you cram the cable wire into the phone jack port?

This won’t work on a bunch of levels for a bunch of reasons.

So AT&T said that the modem I got from Comcast would work with their service. When they said that, I thought, “great. No need to get a new modem and I get a cheaper service.” It turns out the Motorola sb5120 really isn’t supported by AT&T. @eambos: I wish they would just give a new modem for free, but I just don’t know how to demand it from them. @bodyhead: AT&T uses a coaxial cable just like Comcast (at least that’s the case where I live).

Ahh, ok. That’s not DSL then. DSL comes through a twisted pair like your phone lines.

That’s cable. You might actually be able to get that modem working even if they don’t support it. That’s not exactly desirable because if you do need to call tech support, they might not help you if you have an unsupported modem.

I’m guessing the first step would be to register the MAC address (from the modem) with AT&T. The second step would probably be to set up any PPoE settings in the modem (if AT&T requires that on this service).

Is the service already ‘turned on’ at they location where you are trying to hook this modem up?

Typically you lease the modem from Comcast. Are you sure that you don’t have to give that back? They usually will hit you with a huge final bill if you don’t return all of the equipment.

If you are interested in trying to get this working just drop another post and I’ll see if I can grab a manual for your modem. In the meantime, if you would point me to AT&T’s instructions for getting an AT&T approved modem working, we could get started giving it our best shot.

So I actually talked to AT&T already. I don’t remember registering the MAC address with them though. We tried to set up PPoE settings, but that didn’t work out. I noticed that whenever I clicked “Apply”, the number of characters in the password field would change. The rep said that the service was already turned on.

Actually, this whole time, I’ve been talking about my friends’ internet woes. They’re pretty much technology illiterate, so I’m just giving them a helping hand. They said that they’ve actually purchased the modem from Comcast, but they didn’t want to pay for the service again (hence the switch to AT&T).

Here’s a link for AT&T’s product manuals for their modems.

Well give me a bit, I’ll read through it and post a suggestion within a couple of hours.

You can take a cable modem you own and transfer service to another cable provider, but the DOCSIS standard isn’t the same as the DSL standards. Even if you were able to attach twisted pair to a cable modem, they don’t speak the same “language”.

He’s saying that they are both actually cable providers and he is switching from one to the other as per this quote:

AT&T uses a coaxial cable just like Comcast (at least that’s the case where I live)

Really you can have the modem set up a couple of different ways. You said you already tried the ppoe settings. Did you try this with and without @AT&T.com? Sometimes that can make a difference.

Also, tell us what lights are blinking/solid on the front of the modem.

I’ve tried messing with the ppoe settings. I tried with and without @att, using the default account name and password that AT&T provided.

Oh, and all the lights in the front are a solid green. (Except the PC/Activity one, which is orange when my computer is connected to it).