Public/Private Incoming/Outgoing ports

What exactly do "Public" and "Private" mean?

Apple uses these terms to differentiate between the Wide Area Network (WAN) or "Public-side" and the Local Area Network (LAN) or "Private-side" of the router.

Just one question. Why do you think the instructions specify to "Allow Incoming on UDP Port 10000" separately from the previous line which includes that port and others: UDP Ports: 5060, 5061, 10000-11000, 16600-16998, 19305 😕?

In the case of a dedicated Firewall, either hardware or software, you could control both the incoming and outgoing ports. The port instructions you got, most likely, took into account these as well.

In your case, since the 10000-11000 ports were already identified, you will not need to create a separate port map for just the 10000 as per the information you received.

I am guessing the Private IP Address refers to the device on my network I am opening the ports for? Just guessing here, does Private UDP/TCP ports mean "Outgoing" and Public UDP/TCP mean "Incoming"??

You will list all those ports in both the public and private section of the port mapping.

You are telling the airport to open each port .. to the same port on the NAT.. none are outgoing.. it is all incoming.

The NAT does not block any outgoing ports.. just incoming.

To see a good example look at the port mapping for xbox

Xbox Open NAT (Apple Routers)

Obviously yours is using different ports. What is important is to make sure the IP of the VOIP device never changes.. which you do via dhcp reservation.

I have read that enabling NAT Port Mapping Protocol is a security risk.

As long as those ports are opened to a fairly dumb device like a VOIP adapter it is no big deal.

Keep an eye on your VOIP usage.. some VOIP has been compromised and people use it to make cheap calls. Not often in a box behind the main router.. it is usually an issue where the VOIP is built into the router.