FTP Active mode passive mode

FTP Active Mode PORT

The client logs on to the FTP client to connect to port 21 on the server
After successful login, the client randomly distributes a high port for listening (greater than 1024) and notifies the FTP
FTP received the client's notification after using a (N-1 that is, the FTP port minus 1 of the port FTP is 21 so here is 20) port to the client specified high-end port transfer data


20-Port and 21-port open in Iptables
Iptables -I INPUT -p TCP --dport 20-j ACCEPT
Iptables -I INPUT -p TCP --dport 21-j ACCEPT

FTP Passive Mode PASV

When the client connects to FTP, the FTP server randomly assigns a port to transmit the data requested by the client.
The port range specifies an FTP profile within the FTP configuration file:/etc/Vsftpd/Vsftpd.conf

In/etc/Vsftpd/Find Inside Vsftpd.conf

Pasv_min_port=50000Randomly assigned minimum port

Pasv_min_port=60000Randomly assigned maximum port


Also need to set the corresponding port in the Iptables

Iptables-I INPUT-P TCP--dport 50000:60000-j ACCEPT

FTP Active mode passive mode