Cisco Systems Cisco 12816 Manuale Utente

The router also ships with a blank switch fabric card installed in the far left 
(non-working) slot of the switch fabric card cage. The blank filler panel balances 
the air flow through the switch fabric card cage which helps maintain proper air 
flow through the chassis. 

Do not remove the blank filler panel unless instructed to do so by a Cisco support 
representative.

Clock scheduler cards provide the following functionality:

Scheduler—Handles all scheduling requests from the line cards for access to 
the switch fabric.

System clock—Supplies the synchronizing signal to all SFCs, line cards, and 
the RP. The system clock synchronizes data transfers between line cards or 
between line cards and the RP through the switch fabric.

Switch fabric—Carries the user traffic between line cards or between the RP 
and a line card. The switch fabric on the CSC is identical to the switch fabric 
on the SFC.

The second CSC provides redundancy for the data path, scheduler, and reference 
clock. Traffic between the line cards and the switch fabric is monitored constantly. 
If the system detects a loss of synchronization (LOS), it automatically activates 
the data paths on the redundant CSC so data flows across the redundant paths. The 
switch to the redundant CSC occurs within The switch to the redundant CSC 
occurs within sub-seconds (the actual switch time depends on your configuration 
and its scale).

The switch fabric cards augment the traffic capacity of the router. SFCs contain 
switch fabric circuitry that can only carry user traffic between line cards or 
between the RP and the line cards. SFCs receive all scheduling information and 
the system clock signal from the CSCs.