>>"For passive mode data connections, ftpd will listen to a random high TCP >>port. The interval of ports used are configurable using sysctl(8) vari- >>ables net.inet.ip.porthifirst and net.inet.ip.porthilast."
I'm aware of this, but we are running many different kinds of FTP-Servers and partially self developed ftp-applications so that we can't limit the port-range that way.