Strict NAT after port forwarding, DMZ, etc.

Hello, I've recently changed ISPs (from DSL to fiber) and on the first day with the new ISP I had a perfect connection with open NAT on my Xbox One. However, the next day I had strict NAT due to UPnP issues according to the Xbox settings, without changing
any settings or even rebooting my router (Apple AirPort Extreme ac).

Since then I've read multiple posts on multiple forums and already tried pretty much everything there is to try: port forwarding, dmz, turning UPnP on and off, the whole nine yards. One thing I noticed is that even after forwarding the correct ports to my
Xbox's static IP address, if I run a port scan for that address it shows that no ports are open on the device. Am I missing something?

:)

 

Port forwarding question

Essentially the DMZ opens up the IP address to all ports, so saves you setting up manual port forwarding, UPnP, etc.

Using the DMZ doesn't solve the issue for me, because DMZ IPs will use the ports the target service requires, but a port cannot be used by multiple devices at the same time, which is where UPnP is a better alternative, as per my previous post.

I really need the X1 to utilise UPnP to allow it and the 360s to be connected to Live at the same time all with an Open NAT. As it stands, as soon as a 360 talks to Live, it takes the ports and because the X1 isn't using UPnP to assign an alternative port into the service, it falls back to a Strict NAT. What should happen is the first device to connect to the service will use the actual ports and then the next device to use the same service is allocated different ports that it routes into the same service.

 

Strict NAT

I never had to forward ports for my 360.. cleared all port forwarding settings. Disabled dmz. Still have strict NAT. Results of the test, status code 0x4000200004C, detailed nat info says "Your network is behind a port-preserving port-symmetric NAT".. appreciate
the help