- Plesk 12.5 for Linux
FTP does not work in active mode while accessing from external network:
425 Unable to build data connection: Connection timed out
FTP is accessible locally.
TCP port 20, which is used as FTP data port, is filtered by a firewall:
[root@external_server]# nmap -Pn 203.0.113.2 -p 20
Starting Nmap 6.47 ( http://nmap.org ) at 2016-05-14 02:41 NOVT
Nmap scan report for 203.0.113.2
Host is up.
PORT STATE SERVICE
20/tcp filtered ftp-data
Check firewall settings:
# iptables -L -n | grep 20
Allow incoming connections to the port:
# iptables -I INPUT 1 -p tcp --dport=20 -j ACCEPT
# service iptables save
If the port is still being blocked, it is possible, that an intermediary firewall is filtering connections to the port. Contact network administrator regarding the issue.