After the version is upgraded, why the administrator fails to log in

There is difference between versions, so the administrator cannot log in after the version is upgraded.
To differentiate default authentication domains that common users and administrators belong to, V100R003 and later versions add the default domain default_admin for administrators. In V100R002, all users belong to the default domain default. In practice, users often use the default domain default. When the switch is upgrade from V100R002 to a later version, administrators use the default domain default_admin. The configuration of the default domain default_admin is different from that of the default domain default, so authentication fails and the administrator fails to log in.
You can use any of the following methods to solve the problem:
--Run the domain default admin command in the system view to change the administrator domain to default.
--Copy the configuration of the default domain default to the default domain default_admin.
--Enter the user name username@default during login. Ensure that the undo hwtacacs-server user-name domain-included or undo radius-server user-name domain-included command has been executed in the authentication template view.

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