Overview of the Cisco 12008
Cisco 12008 Gigabit Switch Router Installation and Configuration Guide
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Switch Fabric Cards
The SFCs increase the switching capacity of the Cisco 12008. By adding three SFCs to a
router equipped with a single CSC, you increase the bandwidth of each line card slot in the
router from an OC-12 rate to an OC-48 rate.
By adding three SFCs to a router equipped with two CSCs, you not only increase the
bandwidth of each line card slot to an OC-48 rate, but you also provide a fifth (redundant)
switch plane so that the router’s OC-48 data rate can be maintained even if a switch plane
should fail.
In a router with full switch plane redundancy (that is, a router with five available switch
planes), five parallel 1.25 Gbaud serial data streams can be transmitted across the backplane
to and from the router’s line cards. However, only four of the data streams are required for
data transmission purposes; the fifth data stream carries error correction information. If an
error occurs on one of the parallel data streams, data in error can be recovered through use
of the four remaining correct data streams.
You need not install the optional SFCs in a router that uses line cards having an aggregate
bandwidth rate of OC-12 or less. In such a system, a single CSC can provide sufficient
bandwidth to accomplish all the router’s switching and routing functions. Thus, a
minimally configured router does not require the optional switching capacity provided by
the SFCs. To increase the switching capacity of the Cisco12008 to the full OC-48 rate,
however, you must install the three optional SFCs.
Each SFC is mounted on its own card carrier and incorporates an onboard power supply
that takes the –48 VDC supplied by the backplane and converts it into the 3.3 VDC
operating voltage required by the card.