Can you say WOOOPS, we didnt think this through thoroughly....
You may run into this exact issue as well. In case no one has noticed the Comcast Router/Wireless device can only accept 4-5 devices, even if you get 100 to connect only 4 or 5 of them can actually consistently reach the internet. If you setup a router (such as Linksys) on the back of your Comcast device and then a wireless device behind that, you end up with two connections to the Comcast router. Then if a neighbor or two gets on your Comcast device via xfinitywifi is maxed out and even though you have a connection you are unable to get out.
Comcast: Are you going to replace all of our Modems at the same time, or just let this thing DIE on its own with a massive customer exit?
I have a feeling the issue is the same as typical from High Level management decisions throughout the IT world today. They thought of a really cool way to do something like expand their network for free, but they did not have all of the technical information to actually think it through. For the next 6 months or so they are going to feel the brunt of a gigantic mistake in the history of Comcast the 2nd such mistake since they acquired the failing network from AT&T who also bought it and failed to truely stabilize the network failures the previous had deploying it. Like me shortly, alot of well minded customers, in droves and droves, are going back to FIOS or Uverse, maybe even Google Broadband service, for a "reliable" connection even if it is on paper for "less bandwidth" which is irrelevant if you cannot rely on the connection.
Just the wife and myself. Two iphones, two tablets, two laptops.... Comcast router is done, an efficient test for all of you, once the 5th device connects to a brand new SSID WIFI network on the Comcast Router, NONE of the rest are going to have a rewarding experience going forward..... In addition to the 6 devices we above, we also have two webcams- baby room, and front door (door bell camera), the Samsung Frig has a wifi connection, and our thermostat has a wifi connection, I turned off the alarm wifi thinking it was broke only to realize its Comcast.. AGAIN, turned off the Reef Tank WIFI Controller because I couldn't understand why the water temperature was going crazy, the fish weren't getting fed, and I couldn't control it from my iphone even on the local network. Everything connects just fine to whatever SSID Wifi network you create, but when the 5th device connects one of the first four can longer do anything.
Can you say WOOOPS, we didn't think this neighborhood WIFI through thoroughly....
TECHNICAL FOLKS OUT THERE: Gateway mode on your router doesnt solve the entire issue, or even part of it, even if you have purchased all of the proper backend equipment. Any one or all of your devices may end up with an actual Internet Valid IP which you do NOT want for so many reasons, or you may end up going through a HOT router (over worked, poor efficient routing paths) that occurs constantly when a Hundred Thousand Kids get out of school and fire up the XBOX/PLAY station at the SAME Time.