Can't wait to return Comcast modem
937881
Just finished installing a refurbished CM100 on Comcast. Very simple to do. Call to Comcast just required the model and MAC. Sixty seconds later I was surfing again. Speed is either the same or a little faster. I was already getting 6 - 10MB download.  After hanging up with Comcast I recabled my router back in and all computers are blazing. If you are paying monthly rental for modem I would strongly suggest buying your own. I can't believe I have been paying rent for at least 10 years. Yikes that was $3600. Do it now!
3387937
This modem is awesome! Very easy to set up! All I had to do is call Comcast and let them know the serial number and MAC ID and I was online within moments. I have this paired up with a TP-Link Archer C9 AC1900 wireless router http://smile.amazon.com/gp/product/B00PDLRHFW/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 and so far, so good. I chose this modem to future proof in case I need to increase my speed in the future.
4944370
This modem is the EXACT same one that I was leasing from Comcast at $7 a month.  Old modem returned and this will pay itself off in 7 months.

Once you get it plugged in, call Comcast and tell them that you OWN a new modem (my rep got confused that this was another one I got from the Comcast store).  Once they get that straight, give them the MAC address and they will ping it.  Also, if your PC is behind a router (as mine is), you will want to plug a laptop or something in directly to the modem line and bypass your router as Comcast will make you do this for testing.  Do this ahead of time and you won't have to waste 5 minutes as I did.  One last piece of advice, when you return your old modem, GET A RECEIPT that you returned it.  I haven't had an issue, but it wouldn't be below Comcast to try to continue to charge you the $7.

I should have done this YEARS ago!

**** UPDATE ****
Comcast just doubled my speed and the e-mail I received from them stated that some modems would not be able to handle the increase.  I am happy to say that my modem is now handling 40Mbs DL and 15 UP with no issues at all.
211999
Even though the the description says Comcast capable it is not
2054714
I am writting to tell you that i just got back online today. Not with the help of this modem. I am requesting a call tag & refund of the price of this trans action.
4258166
Great modem. Does what it needs to do on Comcast internet
275803
Just got mine set up after having to call Comcast to register it which took about 30 minutes.  Went to speedtest.net on my phone a saw that my speed doubled!  I'm pretty excited about that.  I just hope it holds up.  My old router was a Motorola Surfboard SB6121.
138698
Say hi to Kevin for me! As a very busy guy, he must have forgot that I returned the unit and got my refund already, commenting why I was returning it. Due to the fact that the modem/router combo from Comcast, in my estimation, provides a weak signal, the unit could not receive a steady, stable signal. Moving the modem/ router is not an option and it's placement isn't ideal so no chance of getting it to work. I've tried using the latest signal relay/boosters with the same outcome. I have the same problem using WiFi for my smartphone. The tech help was immediate and helpful but to no avail. I'm sure the lathe & plaster walls in my home are detrimental to the signal as well.
Return of the item was extremely streamlined and quick. Thank you for great service!
522854
This is an excellent device, that I was not able to get connected with Comcast. I called Comcast before I purchased it and they confirmed that it could be connected. However, when I call to get it done, they told me the Modem was End-of-Life and not retail. I was told to go to this website
http://mydeviceinfo.comcast.net/  and click on "latest DOCSIS Devices, then select ONLY from the Retail Column.  Otherwise, Comcast would refused to activate it.  I was ready to dump them and switch to another service, but they are pretty much the same crap or worse. Therefore I am now ordering an Arris TM766G (Retail) http://mydeviceinfo.comcast.net/device.php?devid=405  and hoping Comcast would not change their mind anymore.
UPDATE: I apologize, the new recommended by Comcast and supported is the Arris TM722G.  At least that's what they claim.
3108366
Great modem that works wonderful for a friend of mine.  I would have used it myself, but didn't do my homework first to realize that Comcast cable has compatibility issues with it.
3992758
I bought this modem rather than paying 7 dollar for renting the devices from Comcast. It works very well and it was almost new when I received it . :)
3336895
The modem/router does not work and has never worked. The internet goes out every 20-30 minutes and has to be reset which takes about 5 minutes. I was using a modem and router provided by Comcast before this and did not have any problems.  I have called the manufacturer twice and have been told that it will never work well because I live in an apartment with too many other internet connections near by, but that I can't return it because there's nothing wrong with it.
1368366
Just plugged it in today.  No problems registering and activating it with Comcast.  Works great.
1888409
I bought mine used to the money is gone.

All over a config file. Instead of just writing one for this router Comcast is ignoring the issue completely.
256200
Ive had a Motorola Surfboard extreme SBG6580 DOCSIS 3.0 Wireless N Cable Modem for several years. It has worked flawlessly with my service provider Comcast during the past years. So I ordered another used ARRIS / Motorola Surfboard Gateway SBG6580 Modem for my shore place. It arrived on time and undamaged.  I immediately tested the modem and found it worked. I took it to my shore place for use with the local Comcast service there. What I later discovered it had problems staying active for more than a few days. I checked the internet for possible solutions and found that it had an old version of software and should be upgraded to a new version of software. I contacted Comcast and they told me to buy a new modem with the newer version. There are no warranties with the used modems and you get what you get. For some reason ARRIS / Motorola does not allow software downloads and you must go through your service provider. It will probably be the last used modem Ill ever buy and the last ARRIS / Motorola. Ive been very happy with my Amazon purchases but if you're saving 10 or 20% by buying used  better think again. For you Comcast cable users might want to consider do you want to repay for a new modem every time you have a software upgrade? My conclusion is there must be a modem somewhere that stays up and running 24 and 7 and allows software upgrades...
4792125
Shipping was delayed-arrived two days AFTER I had my appointment with comcast. Tried everything under the sun to configure it, it has been "connecting" for an hour and fifteen minutes.
4266657
I should have done this awhile back & quit paying rental fees!
I got my own router a couple years ago, and am now adding this modem (it is just the modem).
I researched &  chose this one because it offered what I needed at a good price, nice compact size, set up sounds simple & is Comcast compatible.
Yep..all true.
I plugged everything in and then contacted Comcast. This modem IS on their accepted list, and the Rep had me up & running in minutes.
A HUGE BONUS....my internet speed has really increased since I hooked up this modem!
Glad I picked this one. It's working just great!