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Appendix C
Using the ROM Monitor
Debugging Commands
Most debugging commands are functional only when Cisco IOS software has crashed or is aborted. If
you enter a debugging command and Cisco IOS crash information is not available, the following error
message displays:
"xxx: kernel context state is invalid, can not proceed."
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•
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Configuration Register Commands
The virtual configuration register resides in NVRAM. You can display or modify the virtual
configuration register from either the ROM monitor or the operating system software.
To change the virtual configuration register from the ROM monitor, enter confreg by itself for menu
mode, or enter the new value of the register in hexadecimal.
•
Note
Entering confreg without an argument displays the contents of the virtual configuration register and
prompts you to alter the contents by describing the meaning of each bit. In either case, the new virtual
configuration register value is written into NVRAM, but is not effective until you reset or
power-cycle the router.
OL-1957-03
stack or k—Produce a stack trace.
context—Display processor context.
frame—Display an individual stack frame.
sysret—Display return information from the last booted system image. This information includes
the reason for terminating the image, a stack dump of up to eight frames, and, if an exception is
involved, the address where the exception occurred. For example:
rommon 8 > sysret
System Return Info:
count: 19,
reason: a SegV exception
pc:0x802b1040,
error address: 0x802b1040
Stack Trace:
FP: 0x80908398, PC: 0x802b102c
FP: 0x809083b0, PC: 0x802b0b88
FP: 0x809083d8, PC: 0x8017039c
FP: 0x809083e8, PC: 0x8016f764
confreg [hexnum]—Change the virtual configuration register to the value specified. The value is
always interpreted as hexadecimal.
The following display shows an example of the confreg command:
rommon 7 > confreg
Configuration Summary
enabled are:
break/abort has effect
console baud: 9600
boot: the ROM Monitor
do you wish to change the configuration? y/n
enable
"diagnostic mode"? y/n
enable
"use net in IP bcast address"? y/n
enable
"load rom after netboot fails"? y/n
enable
"use all zero broadcast"? y/n
disable "break/abort has effect"? y/n
Software Configuration Guide for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
[n]:
y
[n]:
y
[n]:
[n]:
[n]:
[n]:
Entering the ROM Monitor Mode
C-5
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