Disable IPv6!!!

@Andyr1​ Perhaps you don't do much of anything on your network that would ever run across such problems. Problems with IPv6 do exist and they are totally unnecessary. Just as breaking port forwarding was completely unnecessary, Comcast did it anyway. 

IPv6 is necessary on the public Internet, but NAT negates the need for it in any home network, and the vast majority of business networks. It's a solution looking for a problem, much like the ISO's OSI protocol alternative to TCP/IP. 

@Andyr1​

You're right, most people have no idea of how a network works, or more specifically what ports and port forwarding are, and that's fine, they will never venture into these advanced functions. But then why would Comcast go to the extra trouble and expense to break the advanced functions and make them so dysfunctional for all users/customers?  Comcast has arbitrarily removed functionality that once existed and has now made their equipment unnecessarily limiting and complicated, requiring using a [Edited: "Language"] phone app to do what the gateway web-based console should do, and used to do! The port forwarding function is still in the web console menu, but it no longer works, Comcast intentionally broke it! Why? The menu item for port triggering is still there and still works, but port forwarding has been disabled. This is stupid. Stop apologizing for them. 

Also, currently the [Edited: "Language"] thing has somehow memorized the original DHCP IP address for a device that I have now assigned a static IP address. I use fixed IP addresses for fixed devices, who wouldn't?  The device sometimes shows up in the phone app, but sometimes not, so the phone app is flakey at best. But when the device does appear I select it for port forwarding and define the port & protocol and save it, the Xfinity app shows the wrong IP address and there is no means to enter the correct IP address! Instead of the static IP it uses the old defunct dynamic IP that it originally memorized  and I can't flush it, and if I delete the reserved IP it just comes back. This is not just stupid, it's dysfunctional, so simplified that it's broken. Tell me, how do novice users even begin to deal with this completely unnecessary idiocy? And if novice users have no need for such features, WHY try to dumb down the features for them and break those features in the process?

Stop the stupid!  

PS. I've looked at other cable modems, and I don't care for them, either. They are just modems with a single Ethernet jack (1 gig or 2.5 gig), but no routing function, no NAT, no switch ports, and best I can tell they are all made in [Edited: "Language"] China. [Edited: "Inflammatory"]

Cheers

I also explained a bit about all the multinational sanctions and bans against Chyna's goods, everything I said is easily proven true but the speech police didn't like it. Perhaps because Comcast uses Chyna tech... You can research it yourselves. I hope you will.