C-21
Cisco 3900 Series, Cisco 2900 Series, and Cisco 1900 Series Integrated Services Routers Generation 2 Software Configuration Guide
Appendix C Using ROM Monitor
How to Use the ROM Monitor—Typical Tasks
Router Crashes
A router or system crash is a situation in which the system detects an unrecoverable error and restarts
itself. The errors that cause crashes are typically detected by processor hardware, which automatically
branches to special error-handling code in the ROM monitor. The ROM monitor identifies the error,
prints a message, saves information about the failure, and restarts the system. For detailed information
about troubleshooting crashes, see the Troubleshooting Router Crashes and Understanding
Software-forced Crashes tech notes.
Router Hangs
A router or system hang is a situation in which the system does not respond to input at the console port
or to queries sent from the network, such as Telnet and Simple Network Management Protocol (SNMP).
Router hangs occur when:
• The console does not respond
• Traffic does not pass through the router
Router hangs are discussed in detail in the Troubleshooting Router Hangs tech note.
ROM Monitor Console Communication Failure
Under certain mis-configuration situations, it can be impossible to establish a console connection with
the router due to a speed mismatch or other incompatibility. The most obvious symptom is erroneous
characters in the console display.
If a ROM monitor failure of this type occurs, you may need to change a jumper setting on the
motherboard so that the router can boot for troubleshooting. Procedures for accessing the motherboard
and jumper locations are described in the installation of internal components section of the hardware
installation document for your router.
The jumper to be changed is DUART DFLT, which sets the console connection data rate to 9600
regardless of user configuration. The jumper forces the data rate to a known good value.
Restrictions
Do not manually reload or power-cycle the router unless reloading or power cycling is required for
troubleshooting a router crash. The system reload or power-cycle can cause important information to be
lost that is needed for determining the root cause of the problem.
SUMMARY STEPS
1. stack
or
k
2. context
3. frame [number]
4. sysret
5. meminfo
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