The value of tmnxSubAuthPlcyFallbackAction specifies the
authentication action in case no RADIUS server is available.
When the value is 'deny', all hosts are denied access.
When the value is 'accept', all hosts are granted access.
When the value is 'userDb', the local user database identified by the
value of the object tmnxSubAuthPlcyFallbackUserDb' is used for
authentication.
The value of this object must be set together with the value of
the object tmnxSubAuthPlcyFallbackUserDb.