M20 Router Components

Table 6 lists the major M20 router components and characteristics.

Table 6: M20 Router Major Hardware Components                    

Component	Quantity	Function	Redundant	Field- Replaceable	Offline Button
Cooling system	3 fan trays and 1 rear Routing Engine fan	Cools router components	Yes	Hot-removable, hot-insertable	-
Craft interface	1	Displays the status and allows you to perform control functions	-	Hot-removable, hot-insertable	-
FPC	1-4	Connects PICs to other components and houses shared memory	-	Hot-removable, hot-insertable	Yes
PIC	1-4 per FPC	Provides interfaces to various network media	-	Hot-removable, hot-insertable	-
Power supply	2 AC or 2 DC	Distributes needed voltages to components	Yes	Hot-removable, hot-insertable	-
Routing Engine	1-2	Handles routing protocols and maintains routing tables	Yes	Hot-pluggable	Yes
SSB	1-2	Performs router lookups, manages shared memory, and transfers control packets	Yes	Hot-pluggable	-

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—You can remove and replace the component without powering down the router or interrupting the routing functions.
• Hot-pluggable—You can remove the component without powering down the router, but routing functions are interrupted until the replacement is installed.
• Requires router shutdown—You must power down the router before removing the component.