FTP passive mode configuration, you can also check out this KB article: https://bbs.wftpserver.com/viewtopic.php?f=5&t=5
Use the local IP address.
Fixed IP address
The fixed IP address points to this server, and normally it is the fixed internet IP address.
Get IP from a web file
Get your internet IP from a web file, like: http://ip.wftpserver.com/w/getIP.php
If you are assigned a dynamic IP and are using a service like dyndns.org (or other) to keep your domain name pointing to your IP.
Update IP address interval
If you get your IP from a web file or DNS, the server will update it in the specified time period.
Passive port listener timeout
Specify the timeout for closing the opened passive port listener.
Passive port range
The passive port range is a group of ports assigned for the passive mode, if the FTP server is behind a firewall or router, then you need to forward passive ports in the firewall/router manually.
If you have 100 concurrent FTP connections, you can open 100 passive ports, like 1024 - 1124.
Use LAN IP for PASV response if the client is from LAN
Always use the local IP address of the server machine if the client is from LAN.
Map the Passive mode ports automatically in Wing Gateway
If you use Wing Gateway for the failover or load balancing cluster, and Wing Gateway is also in the DMZ zone, then checking on this option will be very helpful.
It will forward all the passive ports automatically in Wing Gateway. If you have tow or more Wing FTP servers, you need to specify separate passive ports in each server, for example, Server A uses 1024 - 1124, Server B uses 2024 - 2124.
Map the Active mode ports automatically in Wing Gateway
Like the above option, this option is disabled by default, which means Wing FTP server will connect to the FTP client directly for the Active mode transfer, when this option is enabled, then Wing FTP server will let Wing Gateway connect to the FTP client instead.