Field-Replaceable Units (FRUs)

Field-replaceable units (FRUs) are router components that can be replaced at the customer site. Replacing FRUs requires minimal router downtime. There are three types of FRUs:

• Hot-removable and hot-insertable FRUs—You can remove and replace these components without powering down the router or disrupting the routing functions.
• Hot-pluggable FRUs—You can remove and replace these components without powering down the router, but the routing functions of the system are interrupted when the component is removed.
• FRUs that require powering down the router—You must power down the router before removing these components.

Table 2 lists the FRUs for the M40 router.

Table 2: Field-Replaceable Units

Hot-Removable and Hot-Insertable FRUs	Hot-Pluggable FRUs	FRUs That Require Powering Down the Router
Fan tray assembly Flexible PIC Concentrator (FPC) Front and rear impeller assemblies Physical Interface Card (PIC) Power supply	Routing Engine System Control Board (SCB)	Craft interface

For FRU replacement instructions, see Hardware Maintenance and Replacement Procedures.