Here is the question and answer from AT&T about their Fixed Wireless Internet service.
https://forums.att.com/conversations/att-internet-equipment/cant-get-pace-5268ac-into-bridge-mode-pinholes-and-dmz-page-missing-from-setup/5df0286fbad5f2f606be035b?commentId=5f839e7649d3ca03a495518c