I've been fighting with Comcast and constant network issues since "upgrading" to Comcast's Xfi Advanced Gateway for over 3 months now. I never had a problem with my 75 devices connected to my top of the line Netgear router. As of the last 2 weeks, I just cannot connect important devices like Apple computers, iPhones, brand new tablets and Chromebooks, etc... Comcast replaced the gateway yesterday, and the problems are still there. With a master's degree in computer science, I know what heck I'm doing when it comes to networks. Looks like I'm going back to what was working before. Just need to upgrade to a 3.1 DOCSIS modem. Is anyone else successfully able to keep 70+ devices connected to their gateway? Mine USED to for about a month. My last shot is to split the networks to 2.4 & 5, but I know Comcast really frowns on that. I'm tired of trying to explain everything I've tried for the last 3 months to tier 1 & 2 tech support. They have ZERO clue as to what the problem is. Firmware updates? Who knows.
I WAS using a Netgear Nighthawk R7000. (top of the line a few years ago, but NEVER had a problem with running separate networks) I'm currently using Comcast's Xfi advanced gateway. It was great when it worked properly. I finally discovered last night that about 60 connected devices is now about the limit. I had 5 different devices (MacBook Pro, 5K iMac, Sony SmartTV, iPad Pro, and a Samsung Galaxy Note 10+) that would NOT connect to my network last night. I disconnected about 5 other devices (tablets and phones) and THEN those devices successfully connected. I'm sick and tired of power cycling this gateway every day. That's a temporay fix that only lasts a couple hours.
Using the XB6 (TG3482G) here. Are all of those 70 devices on WiFi?
I have about only half that on my LAN and I've never had more than 5 on WiFI at any time, because of issues with WiFi congestion. I'm surprised your old router was able to maintain an active connection to all those devices at once without dropping any, since WiFi routers will drop unused connections to save bandwidth.