How the option "Force server ip to pasv" affects on the transfer?

I use SmartFTP v1.5, I found the option "Force server ip to pasv" in Tools-Settings-Connection
I want to know how does it affect on the transfer?
Thanks.

This option tries to fix wrong server replies in passive mode. If a server is behind a router / NAT and not configured correctly, it may return its internal LAN IP instead of the WAN IP (which gets assigned to the router usually). So SmartFTP replaces the internal LAN IP with the IP that was used to connect to the server, which works around the wrong server configuration.


This option tries to fix wrong server replies in passive mode. If a server if behind a router / NAT and not configured correctly, it may return its internal LAN IP instead of the WAN IP (which gets assigned to the router usually). So SmartFTP replaces the internal LAN IP with the IP that was used to connect to the server, which works around the wrong server configuration.
Thanks a lot for your reply!!!