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Cannot log into EXOS switch after downgrading from EXOS 16 to an earlier release

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TitleCannot log into EXOS switch after downgrading from EXOS 16 to an earlier release
Symptoms
When booted to EXOS 15.7 or earlier, accounts that were created in EXOS 16.1 or higher will report an incorrect password when attempting to log in
Environment
  • EXOS 15.7 and lower
  • Accounts created in EXOS 16.1 and higher
Cause
In EXOS 16.1, the hash algorithm used to store account passwords was changed from MD5 to SHA-256. Any accounts created in EXOS 16.1 or higher will use SHA-256 for hashing the password. Since SHA-256 is not supported prior to EXOS 16.1, these accounts will not work in EXOS 15.7 and below.
Resolution
The failsafe account will still work in EXOS 15.7 and earlier. In order to allow login after downgrading, first configure the failsafe account, and ensure that it is enabled. Note that EXOS will not display the password while it is being entered.
X460-48t.1 # configure failsafe-account
enter failsafe user name: failsafe
enter failsafe password:
enter password again:
X460-48t.2 # configure failsafe-account permit ?
  all             Apply change to all failsafe account access methods
  control         Connections over the control fabric between nodes
  serial          Connections over the Serial Console ports
  ssh             Connections via the SSH protocol
  telnet          Connections via the TELNET protocol
X460-48t.2 # configure failsafe-account permit serial

Once the failsafe account has been configured, you can downgrade to an older EXOS release, then delete and re-create the accounts to save the passwords using MD5. A temporary account must be created, as EXOS will not allow all admin acccounts to be deleted.
X460-48t.2 # create account admin temp admin123
X460-48t.3 # delete account admin
X460-48t.4 # create account admin admin admin123
X460-48t.5 # delete account temp
In the example above, the account "admin" was deleted, and re-created with a password of "admin123".
Additional notes
If you have already booted into an EXOS version prior to 16.1 and are locked out, you can change to the other partition from the BootROM by following these steps.
  • Reboot the switch by unplugging the power and plugging it back in
  • Press and hold the <spacebar> while the switch is booting up to enter the BootROM menu
  • Select the image partition that contains the previous EXOS version by typing the command "boot 1" or "boot 2" (1 for Primary, 2 for Secondary)

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