Product Overview 1-43
Overview of the Cisco 12008
Note The transmission speed of the Ethernet ports is auto-sensing by default and is user
configurable.

Switch Fabric of the Cisco 12008

The heart of the Cisco12008 is the switch fabric circuitry, which provides synchronized
gigabit speed interconnections between the line cards and the RP. The switch fabric
circuitry for the router is incorporated into two cards:
•Clock and scheduler card (CSC)—One CSC installed in the upper card cage is a
standard (required) router component. The CSC represents one plane of switch fabric in
the router. This card is described in greater detail in the section entitled “Clock and
Scheduler Card.”
•Switch fabric card (SFC)—You can install a set of three optional SFCs in the lower card
cage to increase its switching (data-handling) capacity). Each SFC card represents one
plane of switch fabric in the router. This card is described in greater detail in the section
entitled “Switch Fabric Cards.”
To achieve a fully redundant switch fabric with a switching capacity of 40 Gbps, you can
install two CSCs and three SFCs in the router; the second CSC provides redundancy of CSC
functions, as well as redundant switch fabric in the event of CSC or SFC failure.
Each CSC or SFC supports an OC-12 switching rate for the router (622 Mbps). By adding
the set of three optional SFC cards, you can increase the switching capacity of the router to
an OC-48 rate (2.4 Gbps).
Table1-6 lists the switch fabric bandwidth and the switch card configurations needed to
support an OC-12 switching rate or an OC-48 switching rate.