Here are the relevant excepts (e.g., with the login and directory listings omitted). Note that the FTP client on the system freebsd always tries the EPRT command, whether it is using IPv4 or IPv6, and falls back to the PORT command when it doesn't work.
freebsd % ftp aix-4 Connected to aix-4.unpbook.com 220 aix FTP server ... ... 230 Guest login ok, access restrictions apply. ftp> debug Debugging on (debug=1). ftp> passive Passive mode: off; fallback to active mode: off. ftp> dir ---> EPRT 1192.168.42.150484 500 'EPRT 1192.168.42.150484': command not understood . disabling epsv4 for this connection ---> PORT 192,168,42,1,197,52 200 PORT command successful. ---> LIST 150 Opening ASCII mode data connection for /bin/ls. ... freebsd % ftp ftp.kame.net Trying 2001:200:0:4819:203:47ff:fea5:3085 ... Connected to orange.kame.net. 220 orange.kame.net FTP server ... ... 230 Guest login ok, access restrictions apply. ftp> debug Debugging on (debug=1). ftp> passive Passive mode: off; fallback to active mode: off. ftp> dir ---> EPRT 23ffe:b80:3:9ad1::250480 200 EPRT command successful. ---> LIST 150 Opening ASCII mode data connection for '/bin/ls'.
