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B-12
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01
Appendix B
Concepts
Access Lists
Page 177 / 196
C-1
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01
A P P E N D I X
C
ROM Monitor
The ROM monitor firmware runs when the router is powered up or reset. The firmware helps to initialize
the processor hardware and boot the operating system software. You can use the ROM monitor to
perform certain configuration tasks, such as recovering a lost password or downloading software over
the console port. If there is no Cisco IOS software image loaded on the router, the ROM monitor runs
the router.
This appendix contains the following sections:
•
Entering the ROM Monitor
•
ROM Monitor Commands
•
Command Descriptions
•
Disaster Recovery with TFTP Download
•
Configuration Register
•
Console Download
•
Debug Commands
•
Exiting the ROM Monitor
Entering the ROM Monitor
To use the ROM monitor, you must be using a terminal or PC that is connected to the router over the
console port.
Perform these steps to configure the router to boot up in ROM monitor mode the next time it is rebooted.
Command
Purpose
Step 1
enable
Enters privileged EXEC mode.
Enter your password if prompted.
Step 2
configure terminal
Enters global configuration mode.
Step 3
config-reg 0x0
Resets the configuration register.
Page 178 / 196
C-2
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01
Appendix C
ROM Monitor
ROM Monitor Commands
Timesaver
Break (system interrupt) is always enabled for 60 seconds after the router reboots, regardless of whether
it is set to on or off in the configuration register. During this 60-second window, you can break to the
ROM monitor prompt by pressing the Break key.
ROM Monitor Commands
Enter
?
or
help
at the ROM monitor prompt to display a list of available commands and options, as
follows:
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
copy
Copy a file-copy [-b <buffer_size>] <src_file> <dst_file>
delete
Delete file(s)-delete <filenames ...>
dir
List files in directories-dir <directory>
dis
display instruction stream
dnld
serial download a program module
format
Format a filesystem-format <filessystem>
frame
print out a selected stack frame
fsck
Check filesystem consistency-fsck <filesystem>
help
monitor builtin command help
history
monitor command history
meminfo
main memory information
mkdir
Create dir(s)-mkdir <dirnames ...>
more
Concatenate (type) file(s)-cat <filenames ...>
rename
Rename a file-rename <old_name> <new_name>
repeat
repeat a monitor command
reset
system reset
rmdir
Remove a directory
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
Step 4
exit
Exits global configuration mode.
Step 5
reload
Reboots the router with the new configuration register value. The router
remains in ROM monitor and does not boot the Cisco IOS software.
As long as the configuration value is 0x0, you must manually boot the
operating system from the console. See the
boot
command in the “
Command
Descriptions
” section in this appendix.
After the router reboots, it is in ROM monitor mode. The number in the
prompt increments with each new line.
Command
Purpose
Page 179 / 196
C-3
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01
Appendix C
ROM Monitor
Command Descriptions
Commands are case sensitive. You can halt any command by pressing the Break key on a terminal. If
you are using a PC, most terminal emulation programs halt a command when you press the Ctrl and the
Break keys at the same time. If you are using another type of terminal emulator or terminal emulation
software, see the documentation for that product for information on how to send a Break command.
Command Descriptions
Table C-1
describes the most commonly used ROM monitor commands.
Table C-1
Commonly Used ROM Monitor Commands
Command
Description
help
or
?
Displays a summary of all available ROM monitor commands.
-?
Displays information about command syntax; for example:
rommon 16 >
dis -?
usage : dis [addr] [length]
The output for this command is slightly different for the
xmodem
download
command:
rommon 11 >
xmodem -?
xmodem: illegal option -- ?
usage: xmodem [-cyrxu] <destination filename>
-c
CRC-16
-y
ymodem-batch protocol
-r
copy image to dram for launch
-x
do not launch on download completion
-u
upgrade ROMMON, System will reboot after upgrade
reset
or
i
Resets and initializes the router, similar to a power up.
dir
device
:
Lists the files on the named device;
for example, flash memory files:
rommon 4 > dir flash:
Directory of flash:/
2 -rwx 10283208 <date> c870-advsecurityk9-mz
9064448 bytes available (10289152 bytes used)
boot commands
For more information about the ROM monitor boot commands, see the
Cisco IOS
Configuration Fundamentals and Network Management Guide
.
b
Boots the first image in flash memory.
b
flash:
[
filename
]
Attempts to boot the image directly from the first partition of flash memory. If you
do not enter a filename, this command will boot this first image in flash memory.
Disaster Recovery with TFTP Download
The standard way to load new software on your router is to use the
copy tftp flash
privileged EXEC
command from the Cisco IOS software command-line interface (CLI). However, if the router is unable
to boot Cisco IOS software, you can load new software while in ROM monitor mode.
This section describes how to load a Cisco IOS software image from a remote TFTP server to the router
flash memory. Use the
tftpdnld
command only for disaster recovery, because it erases all existing data
in flash memory before downloading a new software image to the router.
Page 180 / 196
C-4
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01
Appendix C
ROM Monitor
Disaster Recovery with TFTP Download
TFTP Download Command Variables
This section describes the system variables that can be set in ROM monitor mode and that are used
during the TFTP download process. There are both required variables and optional variables.
Note
The commands described in this section are case sensitive and must be entered exactly as shown.
Required Variables
These variables must be set with these commands before you use the
tftpdnld
command:
Variable
Command
IP address of the router.
IP_ADDRESS=
ip_address
Subnet mask of the router.
IP_SUBNET_MASK=
ip_address
IP address of the default gateway of the
router.
DEFAULT_GATEWAY=
ip_address
IP address of the TFTP server from which the
software will be downloaded.
TFTP_SERVER=
ip_address
Name of the file that will be downloaded to
the router.
TFTP_FILE=
filename

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