Cisco Systems Cisco 12816 Manuale Utente

Chassis backplane power distribution. –48 VDC power from the power 
supplies is transferred to the chassis backplane. The –48 VDC is distributed 
to all of the cards through the backplane connectors. The blower module 
receives power from the chassis backplane through a wiring harness and 
passes MBus data back to the chassis backplane.

Processor subsystem—Includes redundant RPs, line cards, switch fabrics, 
and two alarm cards. The RP and line cards are equipped with onboard 
processors. The RP downloads a copy of the Cisco IOS image to each line 
card processor. The system uses an alphanumeric display (on each line card 
and RP) to display status and error messages, which can help in 
troubleshooting.

Cooling subsystem—Consists of 2 blower modules, which circulate air 
through the card cages to cool the cards, and fan in each of the power 
modules, which circulates cooling air through the power module.

You can generally determine when and where the router failed during the startup 
sequence by checking the status LEDs on the power modules, and the 
alphanumeric displays on the RP and line cards. 

In a normal router startup sequence, the following sequence of events and 
conditions occur:

The fans in the blower module receive power and begin drawing air through 
the chassis.

The blower module OK indicator is on.

The fan in each PEM receives power and begins drawing air through the 
power supply.

The power supply Pwr OK indicator is on.

As the power on and boot process progresses for the RP and each installed 
line card, the status of each card appears on the alphanumeric display on the 
front panel of the card:

The upper row of the display is powered by the DC-to-DC converter on 
the card.

The lower row of the display is powered by the +5 VDC provided through 
the backplane.