Creating a dummy network may be useful at times where you want to replicate a local network at a different location. For example, the network configuration of one of my development set-ups is dependent on my workplace Wi-Fi network, and I wanted to use the same configuration at my residence as well (for working during out-of-office hours).
This is how I solved the issue on Ubuntu 16.04:
- created a new Wi-Fi network (say Dummy)
- configured settings of the new network to be identical to that of the workplace network config (Now, although the config is present in /etc/NetworkManager/system-connections/Dummy, I cannot connect to it since there's no physical network.)
- converted the network to a Wi-Fi hotspot by editing /etc/NetworkManager/system-connections/Dummy and replacing mode=infrastructure with mode=adhoc (Initially creating a Wi-Fi hotspot and later changing its configuration (as suggested in some forums) did not work in my case, as the network kept on getting reverted back to infrastructure mode during the activation of the hotspot.)
Now, when I turn on my Wi-Fi adapter and connect to the Dummy network (usually via the "Connect to hidden Wi-Fi network" option on the NetworkManager applet menu, as the new network is not visible on the available networks list most of the time), my set-up works just as if it was connected to my workplace network.