Active FTP and Passive FTP

Active ftp, and passive ftp are different in the way how server works in the process of file transfer.  This different impact in how you configure the firewall, if any. 

Active FTP

In active ftp, client connect from random port (>1023), to ftp server port 21.  Then, in data transfer, server send data from port 20.  In firewall setting, you to do the following thing.

In client side firewall, you need to open connection from port 20.

In server side, you need open connection to port 21 from port > 1023, and open connection from port 20 to port > 1023.

Passive FTP

In passive ftp, the first stage is the same with active ftp.  The different is in data transfer.  In passive ftp, the client initiates both connections to the server.

I server side firewall, it need to open connection to port > 1023.