Cisco XR 12406 - Manual (Page 134)

Chapter 4 Troubleshooting the Installation
Problem-Solving with Subsystems
4-4
Cisco XR 12406 Router Installation Guide
OL-13831-01
– All internal DC voltages are within tolerance.
If the AC power source or any of the internal DC voltages exceed
allowable tolerances, the OUTPUT OK LED shuts off, or will shut off
shortly after you turn on the power. Because both the RP (which uses
+2.5, +3.3 and +5 VDC), and the fan tray assembly (which uses –48
VDC) are required for operation, a problem with any of the internal DC
lines can prevent the system from starting up or continuing operation.
For example, if there is a problem with the –48 VDC line that supplies
the fan tray, the system powers up, but will also recognize that the fans
are not operating. The system will initiate a fan failure shutdown
sequence, display the appropriate warning messages, and then shut down
after two minutes.
If there is a problem with any of the other DC lines, the RP will not be
able to initialize the system software, so the system might attempt to start
up and fail during the boot sequence.
• The blower module immediately begins operating.
• The alphanumeric LED displays on the RP indicate the following:
– The left display indicates which RP software component is running.
– The right display indicates the phase of the boot process that is currently
occurring.
Problem-Solving with Subsystems
The key to solving router problems is to isolate the problem to a specific
subsystem. The first step in solving startup problems is to compare what the
system is doing to what it should be doing. Because a startup problem is usually
attributable to a single component, it is more efficient to first isolate the problem
to a subsystem rather than trying to troubleshoot each component in the system.