Let's assume we have friends A, B and C who use the newest Macbooks with factory settings.
The firewall and stealth -mode are not the problem. Remote Apple Events and Xgrid are not needed.
They have used the ip at whatismyip.com unsuccessfully in putting these IPs to the Multiplayer settings in Age II.
They have also tried to use different hexadecimal numbers from the command
ifconfig
These problems suggest me that there is also a better way to solve the problem. Perhaps, by etc/resolv.conf file. It would be great to put all these settings to one or two files, instead of trying to solve the problem graphically.