The NVG599 is needed to connect to the internet. It's is a router, WiFi AP, and phone interface for thier services. No matter what you will need this device to bring internet into your home. The NVG599 does support "bridge mode" which would allow your Orbi to be the primary router and allowing the NVG599 to support your Uverse TV service.
So you are basically going to have two wireless networks running. One for the Uverse wireless reciver which directly connects to the RG (NVG599) and the other wireless which would be the Orbi. I don't remember if the Uverse wireless receivers support 2.4 GHz or 5 GHz now but I am going to assume 2.4 GHZ becuase that is what my old one used.
First lets make sure the Uverse RG is connectable by a PC or other device by ethernet port (makes things easier). If you can't then a tablet can be used via Wifi but there are some things to take care with when the RG is configured.
The first bit informaiton you will need is the login and password to the NVG599. Usually the address is 192.168.1.254 and the password is on a sticker on the NVG599. You won't need the pasword to see the status page but will need it to change firewall settings to allow IP passthough and adjust Wifi settings.
I assume you have the Orbi router already connected to the NVG599 by network cable. Now connect a PC directly to the NVG599 with a network cable or if you only have wirelss use the Wifi. Log into the NVG599 using the above address or what is printed on the label of the NVG599 and you should get a status screen. One of the network devices shows on the status screen, Home Network Devices, should be your Orbi router.
Go into the firewall tab of the NVG599 and you should see a sub tab for IP passthough. If you click on that it will ask for the password of the NVG599, enter it and you will be on the firewall page. You will want to select Password Mode: DHCP-Fixed, and Password Fixed Mac Address select from the drop down your Orbi (it will fill out the right MAC address automatically). Then click on save and you will be forced to reboot the NVG599 for this to take effect.
Once the NVG599 is back up and running you will then have to reboot your Orbi for it to pick up the public IP address from IP Passthough. You can then verify the Orbi getting the public address by logging into the Orib's web management and looking at the Basic tab / Internet and the IP address should not start with 192.168.x.x. This means that the Oribi now has the public address.
The remaiing work is to keep the Wifi network channels seperate. I have the Wifi channel for the NVG599 set for 11 for the 2.4 GHz and 5 GHz disabled. One the Oribi I left auto channel selection set that way it will pick the best channels for your devices. Connect your Uverse wireless recieiver to the Uverse wifi network and all your other devces to the orbi and you are all set.
