Cisco 10000 Series Routers

Field Notice: Cisco ESR10000 Comes Up in ROMMON - Unable to Open disk0:

January 11, 2002

Products Affected

  • ESR-PRE=

  • ESR-PRE1=

Problem Description

Performance routing engines (PREs) shipped as spares do not have their flash disks formatted and they are configured to boot in ROM Monitor (ROMMON).


A PRE which was shipped as a spare (order number ESR-PRE= or ESR-PRE1=) has a blank flash disk and its config register set to 0x0 to boot into ROMMON. Because the PRE was shipped as a spare, the PRE was not installed in a chassis or loaded with an image prior to shipping.

Problem Symptoms

An ESR system comes up in ROMMON if it is booted with a PRE that is still configured as a spare. If the flash disk is unformatted, this message is also displayed when you attempt to issue the dir command on the disk:

rommon 2> dir disk0:
    device does not contain a valid magic number
    dir: cannot open device "disk0:"

Note:?Cisco IOS® Software and boot helper images are more robust than ROMMON and do not have the same issues with new flashdisks. Be aware that this difference between Cisco IOS Software and ROMMON can result in a situation in which an image has been successfully loaded onto the flashdisk with the use of either a boot helper or Cisco IOS Software image, but the device still is not recognized in ROMMON. The cannot open device error message is displayed by ROMMON until the device has been formatted, even if an image already exists on the card.


The workaround to this issue is to ensure that the flashdisk on a PRE is formatted and contains a valid system image before you attempt to boot from it.

The most common method to do this is to install the blank flash disk into a PRE that already runs from Cisco IOS Software. Use the appropriate format disk command, such as format disk0: or format disk1:, and then copy an appropriate image to the flash disk after the format.

If you do not have access to a PRE that already runs a Cisco IOS Software image, you can configure the spare PRE to use its bootflash image. While running from a bootflash image, you can format the disk and load the required image via TFTP. An example of this procedure is shown here:

rommon 1 > confreg
    Configuration Summary
    enabled are:
    break/abort has effect
    console baud: 9600
    boot: image specified by the boot system commands
    or default to: system2-C10K
    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]:
    change the boot characteristics? y/n [n]: y
    enter to boot:
    0 = ROM Monitor
    1 = the boot helper image
    2-15 = boot system
    Configuration Summary
    enabled are:
    break/abort has effect
    console baud: 9600
    boot: the boot helper image
    do you wish to change the configuration? y/n [n]: n
    You must reset or power cycle for new config to take effect
    rommon 2 > reset

After the system has restarted and displays the boot prompt, go to enable mode and format the disk as shown in this example:

c10k (boot)> enable
    c10k (boot)#
    c10k (boot)# format disk0:
    Format operation may take a while. Continue? [confirm]y
    Format operation will destroy all data in "disk0:" Continue? [confirm]y
    . . . (extra periods deleted here) . . ..
    Format of disk0 complete

After the flash disk is formatted, TFTP can be used to load a system image to the disk.

Note:?You need to configure the Fast Ethernet (FE) interface on the PRE (interface f0/0/0) with the appropriate IP address. The TFTP server must be accessible from this interface.

After you use the bootflash image to format and load a flash disk, the config register needs to be changed to a normal value, such as 0x2102, before you do the next router reload command. This register was changed to 0x1 to direct the router to run with the bootflash image in order to format the flash disk.

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

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