Configure FTP server on Synology NAS to be accessible from Internet

On Synology NAS:

 

Configure the FTP server on your Synology NAS:

 

 

Make sure that the neccessary ports are open on the Synology NAS Firewall:

 

 

Select the LAN interface and double click on File Station ports:

 

 

Click on Select:

 

 

Scroll down and find the FTP file server:

Make sure to mark the Enable checkbox and the ports are these you've configured on the first step.

 

 

Click OK when you're done on every subsequent window opened.

 

On your router:

Assuming the Synology NAS LAN IP address is 192.168.1.100

 

Open the control channel port:

 

 

Open the data channel ports:

 

 

Make sure that FTP Application Layer Gateway is turned on:

 

 

You're done. Now you should be able to access your Synology NAS FTP server from the Internet.