And one more argument for using your own quality modem goes on the list. 
Yep, that’s the one I bought. Sounds like I overpaid some, but I bought it with a Best Buy gift card.
I AM NO EXPERT. But from reading the forums at Comcast, the new “wireless gateway” sets up a semi-secret, Comcast-controlled wifi network in addition to your own. it sounds as though your phone is connecting to the new Comcast-controlled wifi hotspot, and your Apple TV is connecting to your old wifi network (now operating from your new modem). Apparently lots of phones will automatically connect to what ever wifi they saw last, and in many cases that’s the Comcast-controlled wifi. If you want your phone to connect to the wifi you control, you’ve got to mumblemumblemumble your phone.
Poke around on the Comcast forums a bit; your situation is not uncommon, and a couple threads discussed remedies.
Thanks I will check out the forums.
The feeling I got from the Comcast forum discussions was that having them change the settings on your Wireless Gateway modem could be impermanent; sometimes customers found that their Gateways had spontaneously reverted to the old setting. Many customers had gotten Comcast to disable the semi-secret second wifi, only to find a couple months later that it had reappeared.
I don’t know enough about modems to know what I’m reading; maybe you can help me.
My home setup is that my Apple Airport is plugged into the modem; the modem has no wireless capabilities at all. I’d like to keep it that way. Is the Motorola 6121 suitable for that sort of setup?
The 6121 doesn’t have built-in wi-fi, so you’d need a wireless router in any case.
When I got fed up with Comcast and was shopping for my own modem, I recall reading, more than once, that the best setup is a separate modem and router. “All-in-one” modem/routers don’t work as well. I don’t remember why.
Just thought I’d mention it, in case anyone else reading this thread is thinking of taking the leap.
Just to put it into this info-flow, I strongly recommend separating all the functions. It can cost a little more, but it gives you better gear (generally) with more optimized functions and easier ways to upgrade and change things one piece at a time.
Motorola 6121 cable modem - Comcast will piss and moan and tell you terrible things might happen, terrible I tell you, but it will give you top-drawer service for years without further costs (which keep going up, for some reason).
A good router/firewall. Any upper-tier consumer or low-end business-grade one, read the reviews.
A good WiFi AP. Unless you have a small house or apartment, I’m a big fan of distributed pucks like Ubiquiti’s Unifi series. One is about the same as most good units and can be positioned unobtrusively wherever it best serves. Poor coverage down in the bedrooms? Add a second one with one simple wiring run. Or two. My three-level house works fine on two of the high-power (LR) units.
Separating all of the functions keeps Comcast out of your business as well. Letting them rent you their crappy modem/router/wifi unit is just paying to take it up the keister, IMVHO.
Thanks so much for this thread! Comcast has been pestering me to “upgrade” our modem for months. I’ve been about to give in, but now I’m going to buy the Motorola modem instead. We already have a router that’s only about a year old.
I really appreciate all the info here.
Oh, so THAT’S why my Comcast modem just stopped working “for no reason.” :mad:
I am convinced the “for no reason” used by Comcast is the same thing Apple is accused of doing when they release a new iPhone; they are accused of quietly degrading the existing iOS for older phones so your only remedy is to upgrade, whether you want to or not.
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Comcast offers several different modem models and not all have wifi routers built in.
If you’re not on DOCSIS 3, you should be anyway, and would greatly benefit from a new modem, whether via Comcast or some other modem compatible with their service.
Any Docsis 3.0 modem is going to be way better than what you have. Motorola SB6121 is fine, Motorola SB6141 is a newer model that I probably would get were I buying a new one today. I personally have a Motorola SB6120 with comcast, which isn’t sold new anymore except for old stock sitting around. The combo units are usually bad because the wireless/router portion sucks, the cable modem part is usually ok. But that isn’t a surprise really because frankly most wireless standalone routers are pretty crappy too unless you install Tomato, DD-WRT, or similar or get some of the very top end ones like the asus RT-AC68U.
I’m bumping this because I want to thank everyone who posted, with special kudos to Rocketeer for starting it. I’d been getting nagged to “upgrade” for awhile and I’d had no idea about creating a hotspot. A few months ago, we finally got one of the Motorolas based on the recommendations here. We really like it and it improved our speed quite a bit. But that’s not why I’m posting.
Last Saturday, for the first time I signed into an Xfinity hotspot at a restaurant. Today I got an email from Xfinity thanking me for trying it, blah blah, here’s a map of hotspots near you. Some of my distant neighbors appear on this map. This is something that never occurred to me: that residential hotspots might be included on a map so random people can come sit in our neighborhood. Creepy. My neighborhood is on the Safe City network and people who don’t belong here are frequently reported. I’m going to talk to my neighbors about this modem.
Another gripe: I still don’t know what the difference is between Comcast and Xfinity, and why we need both names. 
We held out as long as we could, but finally the loss of functionality forced us to ‘upgrade’. The new modem refuses to extend its wifi services to our smart phones (both Samsung, but different service carriers). Our desktop, laptops, and tablets connect just fine, but the phones continue to report authentication errors and ask for the correct password. Reporting it to Comcast has been fruitless. The non-English speaking representatives simply read from their script which tells them to tell me to reboot the modem and then the phone and that will fix my problem. Riiiiight. That’s why your records show this is the 5th call I’ve made to you in so many days reporting the same problem. A power cycle. Right. I’d never have thought to try that BEFORE I CALLED YOU.
The result is, we are connecting our phones through our hotspot. Sigh.
I haven’t seen a difference - pro or con - with speed since the upgrade. I have, however, seen a lot more drops during the course of the day. If you attempt to connect during peak times (10am to 2pm in our area), you will experience slow-loading or non-loading of the larger web pages, but that’s nothing new. It’s always been that way. Definitely not the blazing speed we were promised.
Our only other option in my area is Century Link and they are worse.
I moved back in March, and Comcast kind of insisted that I upgrade to a new modem & such in the process. The price is the same, and they’re throwing in HBO for free, so I didn’t complain. I’m just waiting for them to start charging me more for the “extra” service, and I’ll see if I can downgrade at that point.
Previously, I had cable internet access. Nothing particularly fancy–I don’t play high-end games or spend a lot of time watching super-high-def movies & such.
The move added:
2 digital phone lines. I don’t have a landline phone.
2 WIFI channels, one at 5 ghz for streaming movies, one at 2.4 ghz for friends I don’t like much. I don’t have any wifi devices.
The ability to stream digital cable TV signal directly to my TV, which was what I thought the whole point of cable in the first place… I don’t have a TV.
However, Comcast is saying WE MUST, or assuming you have Comcast Cable, you will not receive any Cable TV.
Personally, I agree I am suspicious about Comcast’s intent. Since this new modem can provide Wifi, one might toss their personal router. However, Comcast conveniently fails to disclose any safety features so one can secure their Wifi through the Comcast modem! I don’t like that, and I am suspicious as to what they can access on my PC if hooked directly to their modem (with router capability). Personally, I want to keep MY router providing Wifi behind a firewall.
Just what evil lurks in the heart of Comcast???
Mine went off without a hitch, and I have one less gadget, my wireless router, to get confused.
Somehow I subscribed to this thread without posting. I bought a modem to replace the rented one, used a wireless router I had, and I’m saving $10.00 a month and have no parasites using my wireless link.