Product Overview 1-69
Overview of the Cisco 12008
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.
Air Filter Assembly
The Cisco 12008 is equipped with a removable air filter that is mounted directly to the
router enclosure in front of the lower card cage (see Figure1-22).
Although the Cisco 12008 will run without an air filter, the air filter should always be
present and maintained properly, especially in dirty or dusty environments.
The air filter assembly serves the following purposes:
•Filters the ambient air being draw into the router by the card cage fan tray.
•Prevents EMI radiation from being emitted into the router’s environment.
A metal honeycomb structure built into the air filter assembly provides EMI
containment.
You are advised to inspect and clean the air filter at least once a month (or more often in a
dusty environment).
Procedures for vacuuming and replacing the air filter are contained in the section entitled
“Cleaning the Air Filter” in Chapter7.
Lower Card Cage and Associated Components
The lower card cage, located directly behind the air filter assembly (see Figure1-22),
houses the card cage fan tray and an optional set of three switch fabric cards (SFCs).
The dimensional characteristics of the SFCs differ markedly from those of the circuit
boards in the upper card cage. Three dedicated slots, numbered SFC0, SFC1, and SFC2 as
you face the lower card cage, are provided to house the SFCs.