Your confidence is cute, but you are incorrect.
Gosh, you make me blush. Condescension isn't needed.
The Mobley is a unified device that contains a router in addition to being an Internet access point. The WAN access point side has a public IP. Everything connected directly to the Internet HAS TO HAVE its own IP (I'm talking access points, not endpoint devices on a LAN). This Internet-side IP is a public IP because it can be used to communicate with other things on the Internet.
Unified device, sure.
Why does the WAN *have* to have a public IP? It can be given another private IP by the att network.
I do exactly this with my mobley and another router to add more devices/wired devices. I'm double NAT'ing. It's nobody's favorite thing to do, but it works most of the time anyway.
Go to a site like
What Is My IP Address? IP Address Tools and More while using a phone or PC connected to the Internet through the Mobley. You will see a public IP listed. Mine is 107.77.83.xx. You can even go to ARIN or another whois site and look up who owns that IP to show that it is AT&T's IP that it has given to your Mobley. In this case it is AT&T:
That is your
public IP. It is the IP your Mobley communicates with. Anything connected to the Mobley sits behind the internal router in the Mobley and has a 192.x.x.x address. Those IPs are not publicly routeable. The public IP on your Mobley is the same type of thing as the WAN IP on a DSL router or a cable modem. It identifies your WAN connection device to the Internet and gives it an address.
Sure, whatismyip. There in lies my proof.
Previous to the mobley, I had AT&T data-only SIM (so, same service, 3.5x more expensive). I then used a fancy "industrial" Bandrich router (from mispot, who went out of business). The whatismyip website did NOT match the WAN that my router gave me. What other conclusion is there than me *not* having a public IP? When I had ISDN, I had port forwarding and dynamic DNS working great. I'm not a novice. With att, I port forwarded and everything else, just like previous, and could not EVER connect from outside. I tried different ports, since AT&T (dsl, anyway) is rather gestapo-like in that regard, and still no dice.
But when traffic is initiated from within your Mobley-supplied LAN it goes out and returns through this public IP and the NAT address the Mobley's router has assigned to your endpoint device (PC, phone, tablet, camera, etc.)
I agree mostly, I just disagree that the mobley is where the public/private happens.
I will say that it's been a few years (long enough for my driver's licence on file with att to expire) since I messed with this. I WANT to be wrong. If you or anyone "out there" is successfully port forwarding / dyndns-ing with att, especially this plan, I'd certainly listen. Obviously one of us has to be wrong, and like I said, I'd prefer that it be me.