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Software Configuration Guide for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
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Appendix C Using the ROM Monitor
Entering the ROM Monitor Mode
Tip
From the Cisco IOS software, you can configure the router to automatically enter the ROM monitor
mode the next time the router boots by setting virtual configuration register bits 3, 2, 1, and 0 to zero.
From the console, enter the following configuration command:
configuration-register 0x0
The new configuration register value, 0x0, is effective after the router is rebooted with the reload
command. The router remains in the ROM monitor and does not boot the operating system.
As long as the configuration register value remains 0x0, you must manually boot the operating system
from the console. Refer to the boot command in the section “Command Descriptions” later in this
appendix.
ROM Monitor Commands
Enter ? or help at the ROM monitor mode prompt to display a list of available commands. For example:
rommon 1 > ?
alias set and display aliases command
boot boot up an external process
break set/show/clear the breakpoint
confreg configuration register utility
cont continue executing a downloaded image
context display the context of a loaded image
cookie display contents of cookie PROM in hex
dev list the device table
dir list files in the file system
dis display instruction stream
dnld serial download a program module
frame print out a selected stack frame
help monitor builtin command help
history monitor command history
meminfo main memory information
repeat repeat a monitor command
reset system reset
set display the monitor variables
stack produce a stack trace
sync write monitor environment to NVRAM
sysret print out info from last system return
tftpdnld tftp image download
unalias unset an alias
unset unset a monitor variable
xmodem x/ymodem image download
rommon 2 >
Note
You can abort any command by pressing the Break key at the console.
ROM Monitor Syntax Conventions
The ROM monitor syntax in this appendix uses the following conventions:
•
Square brackets [ ] denote an optional element. In the following example, the element abc is not
required, but you can specify it if you choose:
•
command [abc]