When I add a docker to a bridge network, normally (when doing it on my local pc) I can leave exposed ports "open" without connecting them to an external port.
This has as advantage that the port itself can only be used from within the network the docker is used, yet invisible to the outside world. Adding a strong layer of protection while making managing of groups of dockers easier. (Non external ports only have to be unique within the network).
However when I add a docker through the GUI in synology - even if I add said dockers to a network and remove them from the default network -, I need to supply a free, unique port per docker. Even if I don't provide anything synology will provide a port by itself using auto
.
How can I prevent this and use dockers only within the network? - In my use case I'd have 4 dockers within a network with only a single docker facing "outwards": a postgres docker, a redis docker, a node docker and the outwards facing docker: an nginx docker acting as reverse proxy & providing the static files.