Product Overview 1-65
Overview of the Cisco 12008
•Cisco Express Forwarding (CEF) memory table—Each line card maintains CEF tables.
These tables, derived from routing tables maintained by the GRP, are used by the line
card processor to make forwarding decisions.
Large networks may require more DRAM to support large CEF tables. For information
on adding memory to a line card, see the document entitled Cisco 12000 Series Gigabit
Switch Router Memory Replacement Instructions.
OC-12c/STM-4c ATM Line Card
The OC-12c/STM-4c ATM line card provides the Cisco 12008 with a 622-Mbps ATM
interface. The card interfaces to the router’s switch fabric, supports from 10 to 40Gbps, and
provides one OC-12c/STM-4c SC duplex single-mode or multimode SONET/SDH
connection. This connection is concatenated, which provides for increased efficiency by
eliminating the need to partition the bandwidth.
Figure1-20 shows a high-level block diagram of the OC-12c/STM-4c ATM line card;
Figure1-21 shows a front view of the card.
Figure1-20 Block Diagram of the OC-12c/STM-4c ATM Line Card
Packet
receive
(Rx)
Forwarding
processor
Packet
transmit
(Tx)
Reassembly
Segmen-
tation
L3 switching
accelerator
Burst
buffer
Burst
buffer
Switch
fabric
interface
Switch
fabric
MBus
module MBus
interface
Buffer
memory
H7695
Silicon
queuing
engine
Buffer
memory
Silicon
queuing
engine
Input
interface
Output
interface