Product Overview 1-49
Overview of the Cisco 12008
This single switch plane of the CSC can be used alone in a minimum router
configuration, or it can be used in combination with another CSC and the three optional
SFCs for full switching redundancy. In the latter case, the per line-card slot bandwidth
of the router is increased from an OC-12 rate to an OC-48 rate, and the second CSC
provides redundancy.
If any one switch plane fails in a fully redundant switch fabric, the failed plane is shut
down, and the router’s full data bandwidth is carried by the surviving planes. The fault
recovery cutover to another viable switch plane typically occurs without loss of data,
because the data path defect is detected while redundancy information is still available,
thus enabling error packets to be repaired “on the fly.”

Housekeeping and Alarm Monitoring Functions of the CSC

The section describes the following housekeeping and alarm monitoring facilities built into
the CSC:
•MBus module— The MBus module on the CSC is a microprocessor-based subassembly
that provides housekeeping services required during router power up and initialization.
It also supports the alarm monitoring LEDs on the CSC faceplate, as described in the
following section.
The MBus module on the CSC operates partly autonomously and partly under the
control of the master MBus module on the RP.
A failed MBus module on the CSC is detected by an MBus polling algorithm running
in the background on the RP.
A failed MBus module detected by this polling algorithm in a redundant CSC
configuration causes the master MBus module to execute an administrative cutover to
the MBus module on the surviving CSC. This cutover is accomplished with no
disruption of normal system operations.
•Alarm monitoring and status functions—The CSC supports the router’s alarm and status
monitoring functions. These functions are described in the following paragraphs.
Figure1-14 shows the location of the alarm contact connector and the various LEDs on
the CSC faceplate through which the system accomplishes its alarm monitoring and
status reporting functions.