Clicking on the Use custom port range checkbox you can set up a well-defined range of ports that FileZilla Server will use for the passive mode. The default suggested custom range goes from 49152 to 65534. A custom port range is recommended if FileZilla Server is connected to the internet via a Network Address Translation (NAT) router. The larger the range, the more concurrent data transfers will be possible. As a rule of thumb, set up the number of ports in the range to be greater than the number of transfers that you want to allow a 4 minutes time periods.
Note: If you are making FileZilla Server available via a NAT router or firewall, make sure to set up the appropriate forwarding rules. To test if it works correctly you might use our online FTP Tester.
If you need the FileZilla Server to be reachable via the internet via its own IP address, enter the host in the Use the following host field. The host can be either an external IP address (for instance, the public IP address of the NAT router) or a hostname that resolves to such IP address.
By selecting the Use default host for local connections checkbox, FileZilla Server will keep using the IP address of the listener that accepts FTP session connections also for passive data connections.