FTP pasivo in plesk panel

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PassivePorts 57000 58000

# /sbin/modprobe ip_conntrack_ftp
# lsmod | grep conntrack_ftp
nf_conntrack_ftp       13696  0
nf_conntrack           61684  1 nf_conntrack_ftp

iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

# /sbin/modprobe ip_nat_ftp

To keep the changes after the system boot, the modules should be added into /etc/sysconfig/iptables-config, toIPTABLES_MODULES line (space-separated).