1. Go to menu Settings ->Advanced ->Port Mapping
2. Add new Port mapping:
Protocol: TCP
Listen IP: unspecified or IP address associated with the domain. Such IP address must be associated with the Internet Interface
Listen Port: 21
Destination IP: enter the IP address of the internal FTP server (e.g.192.168.1.10)
Destination Port: 21
Note: Clients in passive mode will try to open a new connection on port 20. WinRoute will dynamically allocate this port so there is no need to create an additional port mapping.