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Appendix B      ROM Monitor
ROM Monitor Commands
Step 7Enter y to start the download. Successive exclamation points (!!!!!!) indicate that 
the download is occurring. The router reboots when the download is complete.
Updating in Cisco IOS EXEC Mode
Step 1Download the ROMMON image from CCO, and place it on your TFTP server.
Step 2In EXEC mode, save the current configuration, using the copy running-config 
startup-config command.
Step 3Enter the copy tftp rommon command, and answer the prompts. Replace the 
variables shown in the following example with the correct values for your router:
820-2#copy tftp:rommon:
Address or name of remote host []? IP_address_of_remote_host
Source filename []? rommon_image_source_file_name
Destination filename [rommon]? rommon_image_destination_file_name
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
dev                 list the device table
dir                 list files in 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 
						

							 
Appendix B      ROM Monitor
Command Descriptions
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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
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, refer 
to the documentation for that product for information on how to send a Break 
command. 
Command Descriptions
Ta b l e B - 1 describes the most commonly used ROM monitor commands.
Table B-1 Most 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] 
-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 
						

							 
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Appendix B      ROM Monitor
Disaster Recovery with TFTP Download
Disaster Recovery with TFTP Download
The standard way to load new software on your router is using the copy tftp flash 
privileged EXEC command from the Cisco IOS software command-line interface 
(CLI). However, if the router is unable to boot the 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.
tftpdnld 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.  reset or iResets and initializes the router, similar to a power up.
devLists boot device identifications on the router; for example:
rommon 10> dev
Devices in device table:
        id  name
    flash:  flash 
dir device:Lists the files on the named device; flash, for example:
rommon 4 > dir flash:
      File size           Checksum   File name
2835276 bytes (0x2b434c)   0x2073    c806-oy6-mz
boot commands For more information about the ROM monitor boot commands, refer to the 
Cisco IOS Configuration Guide and the Cisco IOS Command Reference.
bBoots 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.
Table B-1 Most Commonly Used ROM Monitor Commands (continued)
Command Description 
						

							 
Appendix B      ROM Monitor
Disaster Recovery with TFTP Download
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NoteThe 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 using the tftpdnld 
command.
Variable Command
IP address of the router.IP_ADDRESS=ip_address
Subnet mask of the routerIP_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
The name of the file that will be 
downloaded to the router.TFTP_FILE=filename 
						

							 
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Appendix B      ROM Monitor
Disaster Recovery with TFTP Download
Optional Variables
The following variables should be set with these commands before using the 
tftpdnld command.
Variable Command
Configures how the router displays file 
download progress.
0—No progress is displayed.
1—Exclamation points (!!!) are 
displayed to indicate file download 
progress. This is the default setting.
2—Detailed progress is displayed 
during the file download process; for 
example:
Initializing interface.
Interface link state up.
ARPing for 1.4.0.1
ARP reply for 1.4.0.1 received.  
MAC address 00:00:0c:07:ac:01TFTP_VERBOSE= setting
Number of times the router attempts 
ARP and TFTP download. The default 
is 7.TFTP_RETRY_COUNT= 
retry_times
Amount of time, in seconds, before the 
download process times out. The 
default is 7,200 seconds 
(120 minutes).TFTP_TIMEOUT= time
Whether or not the router performs a 
checksum test on the downloaded 
image:
1—Checksum test is performed.
0—No checksum test is performed.TFTP_CHECKSUM=setting 
						

							 
Appendix B      ROM Monitor
Using the TFTP Download Command Without Writing the Image to Flash Memory
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Using the TFTP Download Command Without 
Writing the Image to Flash Memory
Follow the steps below to do download new file in ROM monitor mode.
Step 1Use the appropriate commands to enter all the required variables and any optional 
variables described earlier in this section.
Step 2Enter the tftpdnld command as follows:
rommon 1 > tftpdnld [-r] 
NoteThe -r variable is optional. Entering this variable downloads and boots 
the new software but does not save the software to Flash memory. You 
can then use the image that is in Flash memory the next time you enter the 
reload command.
You will see output similar to the following:
IP_ADDRESS: 1.3.6.7
      IP_SUBNET_MASK: 255.255.0.0
     DEFAULT_GATEWAY: 1.3.0.1
         TFTP_SERVER: 223.255.254.254
           TFTP_FILE: c806-sy-mz
Invoke this command for disaster recovery only.
WARNING: all existing data in all partitions on flash will be lost!
Do you wish to continue? y/n:  [n]:
Step 3If you are sure that you want to continue, enter y in response to the question in the 
output:
Do you wish to continue? y/n:  [n]:y
The router begins to download the new file.
Enter Ctrl-C or Break to stop the transfer before the Flash memory is erased. 
						

							 
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Appendix B      ROM Monitor
Configuration Register
Configuration Register
The virtual configuration register is in nonvolatile RAM (NVRAM) and has the 
same functionality as other Cisco routers. You can view or modify the virtual 
configuration register from either the ROM monitor or the operating system 
software. Within ROM monitor, you can change the configuration register by 
entering the register value in hexadecimal format, or by allowing the ROM 
monitor to prompt you for the setting of each bit.
Changing the Configuration Register Manually
To change the virtual configuration register from the ROM monitor manually, 
enter the command confreg followed by the new value of the register in 
hexadecimal, as shown in the following example:
rommon 1 > confreg 0x2101
You must reset or power cycle for new config to take effect
rommon 2 >
The value is always interpreted as hexadecimal. The new virtual configuration 
register value is written into NVRAM but does not take effect until you reset or 
reboot the router.
Changing the Configuration Register Using Prompts
Entering confreg without an argument displays the contents of the virtual 
configuration register and a prompt 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 does not take effect until you reset or reboot the router.
The following display shows an example of entering the confreg command:
rommon 7> confreg
 
     Configuration Summary
enabled are:
console baud: 9600 
						

							 
Appendix B      ROM Monitor
Console Download
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do you wish to change the configuration? y/n  [n]:  y
enable  “diagnostic mode”? y/n  [n]:  y
enable  “use net in IP bcast address”? y/n  [n]:  
enable  “load rom after netboot fails”? y/n  [n]:  
enable  “use all zero broadcast”? y/n  [n]:  
enable  “break/abort has effect”? y/n  [n]:  
enable  “ignore system config info”? y/n  [n]:  
change console baud rate? y/n  [n]:  y
enter rate: 0 = 9600, 1 = 4800, 2 = 1200, 3 = 2400  [0]:  0
change the boot characteristics? y/n  [n]:  y
enter to boot:
 0 = ROM Monitor
 1 = the boot helper image
 2-15 = boot system
    [0]:  0
 
Configuration Summary
enabled are:
diagnostic mode
console baud: 9600
boot: the ROM Monitor
 
do you wish to change the configuration? y/n  [n]:  
 
 
You must reset or power cycle for new config to take effect
Console Download
You can use console download, a ROM monitor function, to download over the 
router console port either a software image or a configuration file. Make sure that 
the Cisco IOS image is in the same PC where you are to perform this function. 
After download, the file is either saved to the mini-Flash memory module or to 
main memory for execution (image files only).
Use console download when you do not have access to a TFTP server.
NoteIf you want to download a software image or a configuration file to the router over 
the console port, you must use the ROM monitor command. 
						

							 
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Appendix B      ROM Monitor
Console Download
Note If you are using a PC to download a Cisco IOS image over the router console port 
at 115,200 bps, ensure that the PC serial port is using a 16550 universal 
asynchronous transmitter/receiver (UART). If the PC serial port is not using a 
16550 UART, we recommend using a speed of 38,400 or less when downloading 
a Cisco IOS image over the console port.
Command Description
The following are the syntax and descriptions for the xmodem console download 
command:
xmodem [-cyrx] destination_file_name
cOptional. Performs the download using 16-bit cyclic 
redundancy check (CRC-16) error checking to validate 
packets. Default is 8-bit CRC.
yOptional. Sets the router to perform the download using 
Ymodem protocol. Default is Xmodem protocol. The 
protocols differ as follows:
Xmodem supports a 128-block transfer size. Ymodem 
supports a 1024-block transfer size.
Ymodem uses CRC-16 error checking to validate each 
packet. Depending on the device that the software is being 
downloaded from, this function might not be supported by 
Xmodem.
rOptional. Image is loaded into DRAM for execution. Default 
is to load the image into Flash memory.
xOptional. Image is loaded into DRAM without being executed.
destination_
file_nameThe name of the system image file or the system configuration 
file. In order for the router to recognize it, the name of the 
configuration file must be router_confg. 
						

							 
Appendix B      ROM Monitor
Debug Commands
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Follow the steps below to run Xmodem:
Step 1Move the image file to the local drive where the Xmodem will execute.
Step 2Enter the xmodem command.
Error Reporting
Because the ROM monitor console download uses the console to perform the data 
transfer, error messages are displayed on the console only when the data transfer 
is terminated. 
If an error does occur during a data transfer, the transfer is terminated, and an 
error message is displayed. If you have changed the baud rate from the default 
rate, the error message is followed by a message telling you to restore the terminal 
to the baud rate specified in the configuration register. 
Debug Commands
Most ROM monitor debugging commands are functional only when the Cisco 
IOS software has crashed or is halted. If you enter a debugging command and 
Cisco IOS crash information is not available, you see the following error 
message:
xxx: kernel context state is invalid, cannot proceed.
The following are ROM monitor debugging commands:
stack or k—produces a stack trace; for example:
rommon 6> stack
Stack trace:
PC = 0x801111b0
Frame 00: FP = 0x80005ea8    PC = 0x801111b0
Frame 01: FP = 0x80005eb4    PC = 0x80113694
Frame 02: FP = 0x80005f74    PC = 0x8010eb44
Frame 03: FP = 0x80005f9c    PC = 0x80008118
Frame 04: FP = 0x80005fac    PC = 0x80008064
Frame 05: FP = 0x80005fc4    PC = 0xfff03d70