The dot1x pae authenticator command enables 802.1x authentication on the port and configures the port as an authenticator. This command is required for the port to initiate the authentication process with the connected client. Without this command, the port will not send EAPOL packets to the client and will not receive the client credentials. Therefore, the client will not be authenticated and will remain in the unauthorized state. The other options are not mandatory for 802.1x authentication, although they can be used to modify the default behavior of the port. For example, authentication open allows the port to grant access to the client before authentication, dot1x reauthentication enables periodic reauthentication of the client, and cisp enable enables Cisco Identity Services Protocol (CISP) on the port. References: Implementing and Operating Cisco Security Core Technologies (SCOR) v1.0, Module 5: Secure Network Access, Lesson 5.1: Implementing 802.1X Authentication, Topic 5.1.2: Configuring 802.1X Authentication, Page 5-9.