Problem Solving Using A Subsystem Approach - Cisco Gigabit Switch Router 12008 Installation And Configuration Manual

Troubleshooting Overview

Problem Solving Using a Subsystem Approach

The key to solving system problems is to try to isolate the difficulty to a specific subsystem.
The first step in solving startup problems, for example, is to compare what the system is
doing to what it should be doing.
Since a startup problem is usually attributable to a single component, it is more effective to
isolate the problem to a specific subsystem, rather than trying to troubleshoot each system
component.
For purposes of the troubleshooting procedures in this chapter, the Cisco 12008 will be
regarded as consisting of the following subsystems:
•
Power subsystem—The power subsystem consists of the following components:
— AC-input power supplies or DC-input power supplies—The Cisco 12008 can be
Note
in the same Cisco 12008 chassis.
— DC-DC converters—A DC-DC converter is incorporated into each of the cards that
•
Cooling subsystem—The cooling subsystem consists of two fan trays: one for the card
cage and one for the power supply bays.
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Cisco 12008 Gigabit Switch Router Installation and Configuration Guide
configured to operate with either source AC power or source DC power.
An AC-input power supply and a DC-input power supply cannot be used together
A Cisco 12008 can be configured to operate with either a single AC-input power
supply or a single DC-input power supply. Adding a second power supply of the
same type provides redundancy (backup power capability) and enables the power
supplies to share the current load for the router.
you can install in the upper card cage (the RP, CSCs, and line cards) or the lower
card cage (the SFCs). The DC-DC converter on each card operates under control of
its onboard MBus module.
The converter takes the –48 VDC supplied to the card through the backplane from
the power supply(ies) and converts it into the +3.3 VDC and +5 VDC required by
the card's circuitry.