After conducting some tests with Synology VPN, I found no way to access the files on DS, from internet, through VPN, port 1723.
All Synology provided applications, File Station, DS Files, DS Photo, WebDav, Audio Station, including DSManager route traffic through them own ports, 5000, 5005, 7000, 80, 21 or for secured SSL through 5001, 5006, 7001, 443 and so on, regardless if the VPN is On or Off. But SSL is not VPN.
I was under the impression that once VPN started between a computer and DS, all traffic goes through the VPN port in order to reach the DS. This doesn't seems to be true.
To test this, with the DS behind a router firewall, simply close all forwarded ports except for 1723 and try to access your files on DS with the VPN on or off. Not working. Once you open the other ports, than you will be able to access your files.
The only way Synology VPN works is to surf the internet through the tunnel so your ip address will show like the DS ip address.
In a enterprise environment the main reason to use VPN is to securely access data/files on the company LAN from an external internet location.
I am missing something here? How I can access my LAN files from internet through VPN? Any help appreciated.