Each type of interface on a J-series or SRX-series device uses a particular medium to transmit data. The physical wires and data link layer protocols used by a medium determine how traffic is sent. See Table 4 and Table 9 for a list of media supported on each type of device.
You must configure each network interface before it can operate on the device. Configuring an interface can define both the physical properties of the link and the logical properties of a logical interface on the link.