Because you are using a 3rd party for the NAT transferral.
I offered to help as I do "firewalls " all day and every day but I'm begining to think that you just want to argue ?
Now you seem intelligent enough not to argue about firewalls will a full time firewall enginner ?
http://community.bistudio.com/wiki/ArmA:_Dedicated_Server
http://forums.bistudio.com/showthread.php?147537-Tutorial-How-to-run-ArmA3-server-on-a-dedicated-server
Firewall issues
By default the Arma 3 server is reporting to Gamespy and it also uses the Gamespy server to negotiate a NAT traversal. If this does not work reliably for you (e.g. when running behind very strict firewall), you may need to open and/or forward following incoming ports:
port UDP (used for game)port+1 UDP (used for server reporting)port+3 UDP (used for VoN transmissions)Following outgoing ports need to be open as well:
port UDP (used for game)port+3 UDP (used for VoN transmissions)Default value of port is 2302, but you may change it by -port command line argument.
Counter example provided, you now look silly :P