I think I've got it figured out. Couple of things to add to this for documentation. To run in LAN only mode, this recipe seems to work well : Disable ethernet on machine you are working with (while adding sync folders and configuring)Under 'Preferences', disable UPnP port mappingUnder each folder share, disable : use relay tracker when required, use tracker server, and search DHT networkUnder each folder, enable : Search LAN, Use Predefined Hosts (and fill in the IP address / port of your "server")It might seem odd to disable the ethernet while making these configuration changes, but it appears that when you add the sync folder, it immediately gets listed by the relay tracker or tracker server, I'm not sure which. Even after setting the settings to be LAN only, it showed up online. I could only get this to stop by resetting the internet connection and getting a new IP address. So it seems we are set - it is a bit of a pain to disable the ethernet adapter when you configure the folders, but it is better than having to reset your internet connection to get them to stay LAN only IMHO. I dont know if it was necessary to fill in a predefined host, it seemed to work without it. But I thought it might be a little bit more restrictive this way. My issue from the original post by the way, was that I had for some reason forgotten to enable Search LAN. That or the fact the shares were tracked from the original install. Not sure. But in either case, seems to be working as hoped.