1. Remember that the goal of low-impact mode is to provide very limited network access to devices without authentication and then provide very specific access to those that have been authorized; this is the least privilege security principle.
2. Low-impact mode uses authentication open but adds security on top of the framework was built in monitor mode. It uses a PACL on the switch port to permit critical traffic of certain endpoints, such as thin clients, to function prior to an attempted authentication. After the authentication, the authorization should provide specific access, unlike monitor mode, which is the same before and after authentication.