I was asking myself one question : does machines provisionned with MaaS must be able to communicate with the region server ? Of course they have to talk to Rack server but is direct communication from machines to Region server mandatory or is it proxied through Rack server ?
All machines proxy communication through the rack controller. A machine in MAAS only needs network access to the rack controller and the Ubuntu repositories. The rack controller itself does need to be able to communicate with a region controller.