On J-series Services Routers, interface ports for the system are located on Physical Interface Modules (PIMs) that you can install in slots on the device. In addition, each device has four built-in Gigabit Ethernet ports in slot 0. Each physical port can have many logical interfaces configured with properties different from the port's other logical units.
Interfaces are named by type, slot number, module number (always 0), port number, and the logical unit number. Port numbering starts with 0. Interface names have the following format:
For example, an interface on port 1 of a T1 PIM installed in slot 3 is named t1-3/0/1. Logical unit 1 on the interface is named t1-3/0/1.1. The built-in Gigabit Ethernet interfaces are named ge-0/0/0 through ge-0/0/3.
For more information about interfaces and interface names, see the JUNOS Software Interfaces and Routing Configuration Guide.