Airport Extreme port settings for No-IP DDNS
How do i configure the port settings to allow this service to reach my desktop? I also have a QNAP NAS that uses DDNS for access.
Remote access to your network is based on what you are trying to do. No-IP does not need port forwarding to work. It is just enabling dynamic IP assigned by your ISP to be picked up by the client you wish to connect back home with.
To access your desktop for example you need to open AFP which is port 548 TCP.
The details for doing this on the airport are here.
https://discussions.apple.com/docs/DOC-3413
I do not think no-ip will work with an airport extreme so you will see Tesserax's recommendation in the article.