NAT Went Strict recently... why?

My NAT changed to STRICT recently, however no settings on my router have changed. All of the appropriate ports are open, and I have multiple Xbox 360's in my house that have an OPEN NAT - it is only my Xbox One that randomly switched to STRICT.

Does anyone have any ideas as to why this happened? Again, no network settings have changed and all of the appropriate ports are opened for my Xbox One IP address. I have it assigned to a fixed IP and the ports are opened for that IP address, as I've always
had it setup, but the NAT randomly just changed.

Again, my Xbox 360's NATs are still open.

Thanks for any assistance.

:)

 

xbox live

Nat type was strict just recently checked

 

Quick Solutions To Installing Games/Add-Ons

With this technique, my NAT went from strict to open. Thanks.

 

If you try to use your One simultaneously with your 360s this will cause issues like strict NAT.

Only solution is to have your router configured to use UPnp instead of portforwarding, which will usually work except on certain routers. The one should get a moderate NAT by this.