similar questions being asked many times, that maybe why
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Installing ROS via CD.ISO will not cause to loose SOFT-ID, unless you do low level format on the Disk (CF or HDD)
Reconfigure the box all over from beginning, will not change the soft-id
even it is asking to keep old configuration when answered as no.
This will only reset the configuration to 0 setting, similar to ‘/system reset’ command on RBs (or console) while it is retaining the original SOFT-ID.
Backup files are and will still remain in the disk even it is resetted, unless it is erased manually.