When the customer was trying to downgrade from V500R001C60SPC300
to usg6000v500r001c30spc600.bin , after
uploading the firmware he was receiveing an error that says it can't be set as
system software file of versions earlier than V500R001C50 does not include any digital
certificate. To load the system software file of an early version, run the set
system-software check-mode all command to set the mode for verifying system
software integrity to all. Otherwise, the file cannot be used for the next
set system-software check-mode all command takes effect once. After the system
restarts, the mode for verifying system software integrity is restored to
command is not included in the configuration file. To view the configuration of
the command, run the display system-software check-mode command.
set system-software check-mode all
Succeeded in setting the check-mode all.
After applying the above command, the downgrade was possible.