Transient Interfaces

The router contains slots for installing FPC boards, and each FPC can accommodate up to four PICs, which provide the actual physical interfaces to the network. These physical interfaces are the router's transient interfaces. They are referred to as transient because you can hot-swap an FPC and its PICs at any time.

You can insert any FPC into any of the router's slots, and you can generally place any combination of PICs in any location on an FPC. (You are limited by the total FPC bandwidth, which cannot exceed the equivalent of an OC-48 link and by the fact that some PICs physically require two or four of the PIC locations on the FPC.)

You must configure each of the transient interfaces based on the slot in which the FPC is installed, the location in which the PIC is installed, and for some PICs, the port to which you are connecting.

You can configure the interfaces on PICs that are already installed in the router as well as interfaces on PICs that you plan to install later. The JUNOS software detects which interfaces are actually present, so when the software activates its configuration, it activates only present interfaces and retains the configuration information for the interfaces that are not present. When the JUNOS software detects that an FPC containing PICs has been inserted into the router, the software activates the configuration for those interfaces.