Subnetwork controllers define the origin of a subnetwork. An individual terminal on a device or junction object is set as a subnetwork controller. Rather than manually setting this using the Modify Subnetwork Controllers pane, you can use the Import Subnetwork Controllers geoprocessing tool to import information about which terminal on a network feature is a subnetwork controller.
The subnetwork controller information must be imported in CSV format. To learn more, see Import a subnetwork controller.