** This example forwards the port 4662 (aMule) **
** These operations must be done by root **

i) Create a folder named ‘natd’ in /Library/StartupItems/

ii) Create two files, ‘StartupParameters.plist’ and ‘natd’, inside ‘natd’ folder

=== Begin of StartupParameters.plist ===

{
Description = “Network Address Translation”;
Provides = (“NAT”);
Requires = (“Network”, “NetworkExtensions”);
OrderPreference = “Last”;
}

=== End of StartupParameters.plist ===

========== Begin of natd ==========

#!/bin/sh
. /etc/rc.common

killall -KILL natd
sleep 5
natd -alias_address 192.168.1.2 -interface en0 -use_sockets -same_ports -unregistered_only -dynamic -clamp_mss -redirect_port tcp 10.0.0.2:4662 4662

========== End of natd ==========

iii) ‘natd’ is a script, so we should set it to be executable

# chmod 755 natd

iv) Reboot your computer.