Connect the AT&T fiber line to the AT&T gateway/ONT
Power on the AT&T gateway/ONT and wait until it is online
Connect an Ethernet cable from the AT&T gateway LAN port to the Deco main unit WAN/LAN port
Open the Deco app and set up the Deco as an Access Point if you want to keep the AT&T gateway handling routing
Open the Deco app and set up the Deco as Router mode if you want Deco to handle routing
If using Router mode, enable IP Passthrough on the AT&T gateway
In the AT&T gateway settings, set IP Passthrough to the Deco main unit
Disable Wi-Fi on the AT&T gateway if you want Deco to provide all wireless
Reboot the AT&T gateway and Deco after saving settings
Connect additional Deco units wirelessly or by Ethernet backhaul
Verify internet access on a device connected to the Deco network