A controller, such as a base station or radio network controller, for a local cellular network or network segment comprising one or more local cells being served by at least one transceiver, the controller communicating with the local cell or cells and comprising controlling means for controlling said local cell or cells and register means for register and share information about the local cell or cells and their relationships and also register and share information about one or more external cells within at least one external cellular network or network segment and their relationships with the local cell or cells. The controller in particular comprises communication means for communicating directly with one or more neighbouring controllers for the external cellular network or network segment, for sharing of the registered information about cells and their relationships. The present invention also relates to a method for said controller and a cellular network including said controller.