Troubleshooting "Unknown error 0" On Catalyst 6500 Series Switch


Fri, 06/29/2012 - 04:12
Jun 29th, 2012


This document shows the steps to troubleshoot the “Unknown error 0” message on Catalyst 6500 Series Switch.


Have basic knowledge on administration of the Catalyst 6500 Series switch.


Getting “Unknown error 0” message on Catalyst 6500 Series switch.

The switch throws the following error message:

  • %Error opening slavesup-bootdisk:/s72033-adventerprisek9_wan-mz.122-33.SXH3a.bin (Unknown error 0)


This issue occurs on switch when you have version mismatch between the redundant supervisors. No action can be done from the active supervisor to the backup supervisor.

Perform the following steps to resolve the issue:

  • Reseat the secondary supervisor physically or reseat it from the primary supervisor.
  • Perform the following steps to ensure that you have the right image on one of the secondary supervisor disks.     
    • You need an external flash, insert it on the active supervisor.
    • Format the external flash by using the format disk1 command on the privileged mode.

    • Copy the correct image s72033-adventerprisek9_wan-mz.122-33.SXH3a to the external flash.

    • Then insert the external flash back to the secondary supervisor.

  • Connect the console cable to the secondary supervisor.
  • Boot the secondary supervisor with the new image by using the following command.     
    • Rommon 1 > boot disk0:s72033-adventerprisek9_wan-mz.122-33.SXH3a


    • Rommon 1 > boot disk1:s72033-adventerprisek9_wan-mz.122-33.SXH3a

  • Once the secondary supervisor is booted up the issue will resolve.


Cisco Catalyst 6500 Series Switches



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