Cisco Router 850 Series Software Configuration Guide

							 
C-1
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01 
APPENDIXC
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.
CommandPurpose
Step 1enableEnters privileged EXEC mode.
Enter your password if prompted.
Step 2configure terminalEnters global configuration mode.
Step 3config-reg 0x0Resets the configuration register. 
						

							 
C-2
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01 
Appendix C      ROM Monitor
  ROM Monitor Commands
TimesaverBreak (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 breakpointconfreg configuration register utility
cont continue executing a downloaded image
context display the context of a loaded image
cookie display contents of cookie PROM in hexcopy Copy a file-copy [-b ]  
delete Delete file(s)-delete 
dir List files in directories-dir dis display instruction stream
dnld serial download a program module
format Format a filesystem-format frame print out a selected stack frame
fsck Check filesystem consistency-fsck 
help monitor builtin command helphistory monitor command history
meminfo main memory information
mkdir Create dir(s)-mkdir more Concatenate (type) file(s)-cat 
rename Rename a file-rename  
repeat repeat a monitor commandreset system reset
rmdir Remove a directory
set display the monitor variablesstack produce a stack trace
sync write monitor environment to NVRAM
sysret print out info from last system returntftpdnld tftp image download
unalias unset an alias
unset unset a monitor variablexmodem x/ymodem image download
Step 4exitExits global configuration mode.
Step 5reloadReboots 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 
						

							
 
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
Ta b l e C-1  describes the most commonly used ROM monitor commands.
Ta b l e C-1 Commonly Used ROM Monitor Commands 
CommandDescription
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
reset or iResets and initializes the r outer, 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  c870-advsecurityk9-mz
9064448 bytes available (10289152 bytes used)
boot commandsFor more information about the ROM monitor boot commands, see the  Cisco IOS 
Configuration Fundamentals and Network Management Guide.
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 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 soft ware 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. 
						

							
 
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. 
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 you use the  tftpdnld command:
VariableCommand
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 
						

							
 
C-5
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01 
Appendix C      ROM Monitor   Disaster Recovery with TFTP Download
Optional Variables
These variables can be set with these commands before using the tftpdnld command:
VariableCommand
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:01
TFTP_VERBOSE=  setting
Number of times the router attempts ARP and 
TFTP download. The default is 7. TFTP_RETRY_COUNT=  
retry_times
Length of time, in seconds, before the download 
process times out. The default is 
 
2,400 seconds (40 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
Using the TFTP Download Command
Perform these steps in ROM monitor mode to download a file through TFTP.
Step 1Use the appropriate commands to enter all the required variables and any optional variables described in 
preceding sections.
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. 
						

							 
C-6
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01 
Appendix C      ROM Monitor
  Configuration Register
You will see output similar to the following:
IP_ADDRESS: 10.3.6.7
IP_SUBNET_MASK: 255.255.0.0DEFAULT_GATEWAY: 10.3.0.1
TFTP_SERVER: 192.168.254.254
TFTP_FILE: c870-advsecurityk9-mzDo 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.
If you mistakenly entered yes, you can enter Ctrl-C or Break to stop the transfer before the flash 
memory is erased.
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 the 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 confreg 
command followed by the new value of the register in hexadecimal format, 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 the confreg command 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. 
						

							 
C-7
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01 
Appendix C      ROM Monitor
  Console Download
The following display shows an example of entering the confreg command:
rommon 7> confreg
      Configuration Summary
enabled are:
console baud: 9600boot: the ROM Monitor
 
do you wish to change the configuration? y/n  [n]:  yenable  “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]:  yenter to boot:
 0 = ROM Monitor
 1 = the boot helper image 2-15 = boot system
    [0]:  0
 
Configuration Summaryenabled are:
diagnostic mode
console baud: 9600boot: 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 either a software image or a 
configuration file over the router console port. 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 dnld command.
NoteIf 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 bps or less when 
downloading a Cisco IOS image over the console port. 
						

							
 
C-8
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01 
Appendix C      ROM Monitor
  Debug Commands
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 do wnload using Ymodem protocol. The 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. The default is to load the image 
into flash memory.
xOptional. Image is loaded into DRAM without being executed.
destination_
file_nameName 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.
Follow these steps to run Xmodem:
Step 1Move the image file to the local drive where Xmodem will execute.
Step 2Enter the xmodem command.
Error Reporting
Because the ROM monitor console download uses the co nsole to perform the data transfer, when an error 
occurs during a data transfer, error messages are only  displayed on the console once the data transfer is 
terminated. 
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 functiona l only when 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, can not proceed. 
						

							 
C-9
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01 
Appendix C      ROM Monitor
  Debug Commands
The following are ROM monitor debugging commands:
 stack or k—Produces a stack trace; for example:
rommon 6> stack
Stack trace:
PC = 0x801111b0Frame 00: FP = 0x80005ea8    PC = 0x801111b0
Frame 01: FP = 0x80005eb4    PC = 0x80113694
Frame 02: FP = 0x80005f74    PC = 0x8010eb44Frame 03: FP = 0x80005f9c    PC = 0x80008118
Frame 04: FP = 0x80005fac    PC = 0x80008064
Frame 05: FP = 0x80005fc4    PC = 0xfff03d70
 context—Displays processor context; for example:
rommon 7> context
CPU context of the most recent exception:
PC  = 0x801111b0  MSR = 0x00009032  CR  = 0x53000035  LR    = 0x80113694CTR = 0x801065e4  XER = 0xa0006d36  DAR = 0xffffffff  DSISR = 0xffffffff
DEC = 0xffffffff  TBU = 0xffffffff  TBL = 0xffffffff  IMMR  = 0xffffffff
R0  = 0x00000000  R1  = 0x80005ea8  R2  = 0xffffffff  R3    = 0x00000000R4  = 0x8fab0d76  R5  = 0x80657d00  R6  = 0x80570000  R7    = 0x80570000
R8  = 0x00000000  R9  = 0x80570000  R10 = 0x0000954c  R11   = 0x00000000
R12 = 0x00000080  R13 = 0xffffffff  R14 = 0xffffffff  R15   = 0xffffffffR16 = 0xffffffff  R17 = 0xffffffff  R18 = 0xffffffff  R19   = 0xffffffff
R20 = 0xffffffff  R21 = 0xffffffff  R22 = 0xffffffff  R23   = 0xffffffff
R24 = 0xffffffff  R25 = 0xffffffff  R26 = 0xffffffff  R27   = 0xffffffff
R28 = 0xffffffff  R29 = 0xffffffff  R30 = 0xffffffff  R31   = 0xffffffff
 frame—Displays an individual stack frame. 
 sysret—Displays 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> sysretSystem Return Info:
count: 19,  reason: user break
pc:0x801111b0,  error address: 0x801111b0Stack Trace:
FP: 0x80005ea8, PC: 0x801111b0
FP: 0x80005eb4, PC: 0x80113694FP: 0x80005f74, PC: 0x8010eb44
FP: 0x80005f9c, PC: 0x80008118
FP: 0x80005fac, PC: 0x80008064FP: 0x80005fc4, PC: 0xfff03d70
FP: 0x80005ffc, PC: 0x00000000
FP: 0x00000000, PC: 0x00000000
 meminfo—Displays size in bytes, starting address, available range of main memory, the starting 
point and size of packet memory, and size of NVRAM; for example:
rommon 9> meminfo
Main memory size: 40 MB.
Available main memory starts at 0x10000, size 40896KBIO (packet) memory size: 5 percent of main memory.
NVRAM size: 32KB 
						

							 
C-10
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01 
Appendix C      ROM Monitor
  Exiting the ROM Monitor
Exiting the ROM Monitor
You must set the configuration register to a value from 0x2 to 0xF for the router to boot a Cisco IOS 
image from flash memory upon startup or reloading. 
The following example shows how to reset the configuration register and cause the router to boot a 
Cisco
 IOS image stored in flash memory:
rommon 1 > confreg 0x2101
You must reset or power cycle for new config to take effect:
rommon 2 > boot
The router will boot the Cisco IOS image in flash memory. The configuration register will change to 
0x2101 the next time the router is reset or power cycled.