I have a NAS Synology beyong my Internet Box. On the Internet Box, I have UPnP not activated and I have only activated on Port Transfer the following ports : 1701/UDP, 500/UDP and 4500/UDP which are usefull for my L2TP VPN. Even that, my Cloud Station is accessible outside of my local network. Regarding the definition of port forwarding of Synology https://www.synology.com/en-us/knowledgebase/faq/299, the port 6690 should be opened. I do also a verification of opened ports by http://www.portchecktool.com/ and the 6690 port is close.
Has someone any idea on how cloud station works with this port closed ?
