Using External Router on a Combo Modem/Router ???

Microsoft bought Nokia.. then I thought some company HMD global took over designing the Nokia devices..
Yes that is all there is to it. Your 2600 router will be doing nothing more than converting packets from wireless to wired and sending them unchanged to the T-Mobile box.

The separate AP allows you to deploy a strong wifi signal where the users are, with the T-Mobile box remaining placed for best cellular signal.

Configured for "passthrough," "bridged," or "dumb AP," the AP box will do no DHCP assignments, routing, NAT, or firewalling. Those functions are all handled by the main router. The main router sees users of the AP as a group of wired clients.

This means no special configuration of the main router is needed to add one or more dumb APs to the network. They are served like wired clients.
Just wanted to say thanks again. Not sure how I did it, well sort of I am but no where close to the understanding part. But sort of. I have a lot going on this past week into next and sort of trying stuff on the fly to stay busy.

Yay, I have my 2 month old Motorola 2600 hooked up via Powerline adapter to the TMobile Modem/router
Since the TMobile does not allow any changes to its set up in the GUI except for SSIDs and passwords, this was an awesome solution. Motorola as an access point.

Lets keep in mind the Motorola 2600 GUI isnt exactly loaded with options but makes the TMobile look like kindergarten in comparison.
So in the Motorola I did exactly what we discussed, as best I can tell.
First I configured the Motorola with it hooked via Ethernet directly to my laptop off the network. Changed the settings, turned off whatever I could find with DHCP ect. also made sure it had a different 168.yadaya day from the TMobile *LOL*
Hooked it all up and working, then went into the Tmobile and turned off the wifi.

Went back into the Motorola and turned off whatever else I could except wifi (this is almost funny because I really dont know what I am doing except trying to follow peoples suggestions and internet stuff) restarted the Motorola.
Now with the Motorola back in the center of the home, Tmobile in the most southern part and used as a modem only. My security cameras bring up video at the snap of a finger, almost literally, DB camera the same, wifes work station Ethernet is plugged into the back of the Motorola and working perfect.
Motorola Router is in the middle of the second floor with Powerline adapter to the lower level TMobile.

I have the Powerline adapter plugged into the Motorola Ethernet port, not the WAN port and also my wifes workstation plugged into the Ethernet. Really kind of cool, Im sure I find a mistake someplace *LOL*

But as of right now, all 4 cameras work, DB cam works, Roku boxes work, all wifi things work and work well, Wifes work VOIP landline works, home VOIP landline works, ect. Oh and the two wifi laserjets work. Im sure something wrong will turn up OR I got extremely lucky but I enjoy this stuff as a hobby and learning, as long as it works when I am done ... time will tell and if any input from anyone more then welcome....
well I think I have the Motorola 2600 AC router correctly hooked up to the T-Mobile router and modem combination through the powerline adapter.
All the Wi-Fi devices showing up as ethernet connections on the TMobile unit and the IP addresses on the Wi-Fi devices show the T-Mobile unit IP address and not the Motorola router.
I’m pretty sure that means everything is correct and no double NAT as you guys were describing.
Thanks for everybody’s help feel free to chime in if I missed anything, I also read some articles on CNET and google support regarding double NAT.