IOU tools
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IOU Tools


IOU tools are used to manipulate the IOU NVRAM file.

The following tools are available:

  • iou_export: exports startup/private configuration from IOU NVRAM file.
  • iou_import: imports startup/private configuration into IOU NVRAM file.

The IOU tools are based on Dynamips, see


This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2 as published by the Free Software Foundation.

The full license text is available in the file LICENSE.


Python 2.7 or 3.x is needed. Only standard modules are used.


  • When iou_import creates a new NVRAM image, it can't know, which IOU it will use. Therefore on the first saving of the startup-config within IOU you might get the warning "Attempting to overwrite an NVRAM configuration previously written by a different version of the system image."

    You can ignore this warning.

    This doesn't happen, if an existing NVRAM image is updated by iou_import.

  • iou_import will not compress the startup-configuration.

    Therefore if you extract a compressed configuration with iou_export and then re-import it with iou_import, the NVRAM usage will increase. If the flash size is quite small, you might get the error message "NVRAM size too small".

    In this case increase the NVRAM size.