Troubleshooting Overview
Cisco 12008 Gigabit Switch Router Installation and Configuration Guide
5-4
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 Cisco12008 will be
regarded as consisting of the following subsystems:
Power subsystemThe power subsystem consists of the following components:
AC-input power supplies or DC-input power suppliesThe Cisco12008 can be
configured to operate with either source AC power or source DC power.
Note An AC-input power supply and a DC-input power s upply cannot be used together
in the same Cisco12008 chassis.
A Cisco12008 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.
DC-DC convertersA DC-DC converter is incorporated into each of the cards that
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 +3.3VDC and +5 VDC required by
the cards circuitry.
Cooling subsystemThe cooling subsystem consists of two fan trays: one for the card
cage and one for the power supply bays.