Interesting I have my own modem with a static IP running on Comcast with no issues. I never even thought to ask when I switched from my "rental modem". I just bought one and plugged it in. The first time I logged in to my computer the browser defaulted to the Comcast site saying I needed to authorize the modem. Went through some simple verification questions and 5 minutes later was up and running. Never spoke to anyone to hook it up, have not had any problems, and still have my static IP.

Do you have a "real" static IP or just an IP that never changes? For a static IP you can call Comcast and request to change the PTR for that IP.

Also do you have a business or residential account?

I believe only business class accounts can get real static IP's, unless possibly you can pay $10 or so extra a month for the service on a residential account.

I've never had the need for one as my IP address hardly ever changes, and if it does I've just had a cronjob that updates Route53 automatically every $X hours so it isn't an issue.

Also here is a site made by Comcast showing you what DOCSIS type modems are compatible with their service. You can bring your own cable modem without issue. I would call their number, tell them you need to hook up your modem because you've upgraded and give them the MAC and that will be the end of it.

http://mydeviceinfo.comcast.net/

I did that and they told me that I bought a modem off their list that isn't sold commercially so they wouldn't attempt to let me use it.

Apparently there are only a select number of DOCSIS 3.0 cable modems that support multiple static IPs.

As a note - even though your IP may not change - the rest of the world knows it's a residential IP and many email servers will automatically bounce email from you.

I own a Zoom 5341 that I went out and bought just because it was DOCSIS 3.0. I had no idea that list even existed at the time but my modem happens to be on the list.

No one questioned what make/model I had at the time, I just gave them my MAC and I was on my way. The networking folks have been helpful and just did what I asked and we were on our ways.

I don't know if they would have flagged anything if my MAC didn't happen to be in range of an approved company and I would have gotten any grief; I'd buy one off that list from Amazon and return the Comcast provided one.

I have a "real" static on a residential account. I think it is an extra $5 or $10 I pay monthly for it. When I first got it (about 2 or 3 years ago) they fought me a little on the residential account part, but I went to the office and talked with a manager there face-to-face who was able to get it done for me. I luckily live about a mile from a local office and have always had much better luck with the face-to-face customer service for any of my issues (although I have learned that just asking to be transferred to the retention department usually results in better outcomes on the phone).