FTP through HAProxy

I found out the solution. It seems I had to use a directive pasv_address with the IP of the system. I will post again the settings I've used to make it work.

Supposing our public IP is 217.130.100.62, here we have an extract of /etc/vsftpd.conf in the Guest:

# Passive mode
tcp_wrappers=YES
pasv_address=217.130.100.62
pasv_enable=YES
pasv_promiscuous=NO
port_enable=YES
port_promiscuous=NO
pasv_min_port=10000
pasv_max_port=10250

And here, a simplified directive in /etc/haproxy/haproxy.cfg in the Host:

listen FTP :21,:10000-10250
    mode tcp
    server ftp01 192.168.122.152 check port 21