I have a Synology usbstation2. On my iPad and iPhone I have added the Nas automatically and could use it as a mediaplayer to stream to Apple tv. Once added with the internal IP and one entry with the extrernal IP.
After some time (half day?) in the opening screen the device changes from Synology Usbstation2 Digital Media Server into Unknown Digital Media Server.
Does not function anymore then.
After rebooting the Synology it is back to normal again.