Vsftpd: why the passive port range is not followed?

I configure vsftpd for passive mode

Code: listen=YES
log_ftp_protocol=YES
pasv_enable=YES
pasv_address=192.168.0.2
pasv_min_port=10090
pasv_max_port=10100It works but use random ports!

Look output of ss during transfer

Code:tcp ESTAB 0 0 192.168.0.2:33150 192.168.0.2:21 users:(("ncftp",pid=14411,fd=4)) timer:(keepalive,119min,0) uid:1000 ino:236010 sk:400b cgroup:unreachable:1 <->
tcp ESTAB 0 0 192.168.0.2:44985 192.168.0.2:20 users:(("ncftp",pid=14411,fd=7)) timer:(keepalive,119min,0) uid:1000 ino:246607 sk:4011 cgroup:unreachable:1 <->this is ok..without firewall, with firewall and redirect port for nat is a serious problem
Why vsftpd use random ports?

I have tried

Code: listen_ipv6=NOand disable pasv_address option. But nothing

This is the complete configuration, actually

Code: anonymous_enable=YES
connect_from_port_20=NO
dirmessage_enable=YES
ftpd_banner=Welcome
listen=YES
listen_ipv6=NO
local_umask=022
log_ftp_protocol=YES
ls_recurse_enable=YES
pasv_address=192.168.0.2
pasv_enable=YES
pasv_max_port=10100
pasv_min_port=10090
seccomp_sandbox=NO
xferlog_enable=YES
xferlog_file=/var/log/vsftpd.log
xferlog_std_format=YES