The invention relates to a network of luminaires for an automatic lighting system comprising at least two luminaires (1) and at least one controller, each luminaire comprising a light source (4) and at least two communication ports (3, 6, 9, 12), wherein the communication ports have predetermined configuration and orientation (3, 6, 9, 12), each communication port (3, 6, 9, 12) is adapted to be communicatively connected to a communication port of another luminaire (1) in said network in the direction and orientation of the port (3, 6, 9, 12), and wherein the identification of unused communication ports (3, 6, 9, 12) is communicated to said at least one controller. The invention further relates to a plug (20, 21, 24, 28) adapted to be inserted into unused communication ports (3, 6, 9, 12) in a luminaire of a network of luminaires (1), said plug (20, 21, 24, 28) being adapted to indicate to a controller (7) in said network that the communication port (3, 6, 9, 12) is unused for communication to another luminaire; and to a method of auto-commissioning of a network of luminaires, wherein the method comprises the steps of: identifying unused communication ports (3, 6, 9, 12), communicating identified unused ports to said at least one controller, and control at least one luminaire as a function of the received information related to unused communication ports.