RBR50 and ATT Fiber?

Just to be clear: If the AT&T box creally can be put into "IP pass-through" mode, then only one device can be connected to the AT&T.

If the Orbi router is factory reset (not just 'reset') and the WAN (yellow) port is connected to the AT&T router (with the AT&T router in its default mode), then this should happen:

• The Orbi router should go through a 2-3 minute boot up sequence, with the ring light at the top 'blinking', and then 'fading', and finally turning blue.
• There should be a new WiFi network matching the information on the router product label, i.e. the WiFi SSID should be ORBIxx and the WiFi password should match the product label.
• At this point, there will be two WiFi networks in the house, one from AT&T and one from Orbi.
• Devices connected directly to the AT&T box will get IP addresses from the AT&T box.
• Devices connected to the Orbi will get IP addresses from the Orbi.
• Yes, this is the dreaded "Double NAT" https://kb.netgear.com/30186/What-is-Double-NAT
• Every device should be able to reach the internet.
• Notice there has been no mention of the Orbi 'app'.
• If you want to change the SSID/password (perhaps so that a whole bunch of WiFi devices do not have to be reconfigured, then either connect a web browser to http://orbilogin.net (with credentials "admin" and "password") or connect a smartphone to the Orbi SSID and open the app.

Many customers would just "leave well alone" and stop here.

Others might decide to disable the AT&T WiFi (a pointless signal competing with their Orbi WiFi).

If all devices are connected to the Orbi (only the Orbi connected to AT&T), nearly everybody can just get on with life.

If you need one of the applications that is affected by Double NAT, then you have two choices:

• Put the Orbi into Access Point (AP) mode, or
• Put the AT&T into "pass-through" or "bridge" mode.