Cisco XR 12404 - Manual (Page 103)

4-5
Cisco XR 12404 Router Installation Guide
OL-13830-02
Chapter 4 Troubleshooting the Installation
Problem-Solving with Subsystems
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.
For troubleshooting purposes, the Cisco XR 12404 router consists of the
following subsystems:
• Power subsystem—Includes the following components:
– AC-input power supplies or DC-input power entry modules (PEMs). The
Cisco XR 12404 router can be configured for source AC or source DC
power (you can not mix AC and DC power).
– Chassis backplane power distribution. The –48 VDC power from the
power supplies is transferred to the chassis backplane, which distributes
–48 VDC power to the cards in the card cages through the backplane
connectors.
– DC-DC converters. Each card in the router is equipped with DC-to-DC
converters. These converters are controlled by the MBus module on each
card. The DC-to-DC converters take –48 VDC and convert it into the
voltages required by the card circuitry.
• Processor subsystem—The processor subsystem includes the RP and all line
cards. The RP downloads a copy of the Cisco IOS XR image to each line card
processor. The system uses alphanumeric LED displays to display status and
error messages, which can help in troubleshooting.
• Cooling subsystem—The cooling subsystem is comprised of one fan tray
assembly and one air filter. The fan tray assembly and air filter are
hot swappable, and can be replaced while the system is running.
Caution Replace the fan tray assembly within 2 minutes of removing it from the
chassis or the router will go into a critical failure mode and shutdown
due to an overtemp condition.
todd.book Page 5 Monday, March 16, 2009 2:47 PM