Trying to get a Synology NAS as an FTP server through the ATP500. Created rules, policies etc. but still the build in FTP kicks in. When disabling it the FTP connections get refused.
The default FTP port on ATP is port 21, so you can either change the default port of ATP and user port 21 for Synology NAS, or use another external port for port mapping in NAT rule.
Using another external port for port mapping in NAT rule
The FTP server still uses port 21.
On ATP500, configure port mapping. Port 2121 is mapped to port 21.
Create a security policy rule for WAN to LAN, server IP, service: FTP(port 21), allow.
On the FTP client, connect to NAS via ATP’s WAN IP: 2121.
Thank you very much, it's resolved now. I was struggling with the internal FTP. When moving it to another port it worked. Please close this case.