Miscellaneous NAT Configuration Tips

Don't forget to add "option GATEWAY" to the kernel config file or NAT will
not work.  NAT requires IP packet forwarding.

You must have IPF enabled even if you aren't using it for anything or
NAT will not work.  The standard way to do this is to make sure
/etc/ipf.rules is installed and edit /etc/rc.conf changing
"ipfilter=NO" to "ipfilter=YES" then reboot.