The 802.1X authenticator operates as a go-between with the supplicant and the authentication server to provide services to the network. When a switch is configured as an authenticator, the ports of the switch must then be configured for authorization. In an authenticator-initiated port authorization, a client is powered up or plugs into the port, and the authenticator port sends an Extensible Authentication Protocol (EAP) PDU to the supplicant requesting the identification of the supplicant. At this point in the process, the port on the switch is connected from a physical standpoint; however, the 802.1X process has not authorized the port and no frames are passed from the port on the supplicant into the switching engine. If the PC attached to the switch did not understand the EAP PDU that it was receiving from the switch, it would not be able to send an ID and the port would remain unauthorized. In this state, the port would never pass any user traffic and would be as good as disabled. If the client PC is running the 802.1X EAP, it would respond to the request with its configured ID. (This could be a username/password combination or a certificate.)
After the switch, the authenticator receives the ID from the PC (the sup- plicant). The switch then passes the ID information to an authentication server (RADIUS server) that can verify the identification information. The RADIUS server responds to the switch with either a success or failure message. If the response is a success, the port will be authorized and user traffic will be allowed to pass through the port like any switch port connected to an access device. If the response is a failure, the port will remain unauthorized and, therefore, unused. If there is no response from the server, the port will also remain unauthorized and will not pass any traffic.
The following configuration settings are required in the switch to make
802.1X function work:
