@bluetrain
> This doesn’t seem to be an issue and comports with everyone’s guides online for configured IP passthrough mode on the BGW320-505 and, in fact, Opnsense does show my WAN IP address as my actual address (something it did not before!).
This corroborates my assessment. You were previously in a double NAT situation. You saw your WAN IP on your gateway because your WAN IP was your gateway, not your interface IP. You now see the ISP’s head end IP as the gateway due to IP passthru
@bluetrain
> The strongest example I’ve uncovered of this is, from my WAN (or LAN) directly accessing my WAN IP.
What have you been testing from? Laptop pointed to LAN IP, laptop pointed to WAN IP, and cellphone with WiFi disabled pointed to WAN IP?