21 Oct 2014 
Support Center » Knowledgebase » How to load an IOS onto a Cisco router using the ROMmon mode
 How to load an IOS onto a Cisco router using the ROMmon mode
Solution

To load an IOS onto a router using ROMmon mode via Ethernet cable:

  1. Start the TFTP server (make sure the file path is correct and that you allow both transfer and receive)
  2. Connect to the router via Ethernet cable (an Ethernet cable is preferred due to the large size of the file and the maximum speed that data can travel over the console cable)

¨ Before the IOS is loaded it is important to make sure that your router has enough memory to support the IOS. The router will allow an IOS to be loaded even if there is not enough memory, in this case a smaller IOS will have to be loaded.

  1. At the rommon prompt enter the following commands (commands are case sensitive, and the use of the directional arrows and tab auto complete function is not allowed):

 
IP_ADDRESS=IP address of the Ethernet port
IP_SUBNET_MASK=subnet mask of the Ethernet port
DEFAULT_GATEWAY=the default gateway
TFTP_SERVER=the IP of the TFTP server (your local computer)
TFTP_FILE=the file name of the IOS file
tftpdnld

  1. The router will then issue a warning message:

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]: y

  1. Enter y, and the IOS will load
  2. Once loaded you must boot up the new IOS by issuing the boot command


To load an IOS onto a router using ROMmon mode via the Cisco console cable:

  1. Connect to the router using the light blue Cisco console cable (make sure the RJ-45 connector is plugged into the console port on the router) using the 9600-8-N-1 settings. The next two steps (changing the console baud rate) are optional.
  2. In ROMmon mode, change the baud rate to 15200 using the confreg command.

rommon 1>confreg
Configuration Summary
enabled are:
break/abort has effect
console baud: 9600
boot: the ROM monitor

¨ The router will guide you through changing the registry. You want to press y to chang the configuration. The only other change you need to make is the change to the console baud rate, set that to 7 (115200).

do you wish to change the configuration? y/n [n]: y
enable "diagnostic mode"? y/n [n]:
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]:
disable "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
4 = 19200, 5 = 38400, 6 = 57600, 7 = 115200 [0]: 7
change the boot characteristics? y/n [n]:
 
Configuration Summary
enabled are:
break/abort has effect
console baud: 115200
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.

 rommon 2>

  1. When you reset the router in your console window you will see characters that you cannot read. You have to stop the session and set your baud rate to 115200. This will let you increase the speed that you use to transfer the file.
  2. At the rommon prompt enter xmodem -c {filename}
  3. When prompted, enter y to continue
  4. From your hyperterminal prompt, click on transfter then send file
  5. Select the IOS image then change the protocol to xmodem via the dropdown box then click send.
  6. After the IOS has been downloaded, change the boot order by using the confreg 0x2102 command.

 



Article Details
Article ID: 1
Created On: 16 Sep 2006 06:51 AM

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