Cisco 3560G 48TS Software Configuration Guide - Page 200

Understanding 802.1X Port-Based Authentication Chapter 9 Configuring 802.1X Port-Based Authentication Ports in Authorized and Unauthorized States Depending on the switch port state, the switch can grant a client access to the network. The port starts in the unauthorized state. While in this state, the port disallows all ingress and egress traffic except for 802.1X, CDP, and STP protocol packets. When a client is successfully authenticated, the port transitions to the authorized state, allowing all traffic for the client to flow normally. If a client that does not support 802.1X is connected to an unauthorized 802.1X port, the switch requests the client's identity. In this situation, the client does not respond to the request, the port remains in the unauthorized state, and the client is not granted access to the network. In contrast, when an 802.1X-enabled client connects to a port that is not running the 802.1X protocol, the client initiates the authentication process by sending the EAPOL-start frame. When no response is received, the client sends the request for a fixed number of times. Because no response is received, the client begins sending frames as if the port is in the authorized state. You control the port authorization state by using the dot1x port-control interface configuration command and these keywords: • force-authorized-disables 802.1X authentication and causes the port to transition to the authorized state without any authentication exchange required. The port sends and receives normal traffic without 802.1X-based authentication of the client. This is the default setting. • force-unauthorized-causes the port to remain in the unauthorized state, ignoring all attempts by the client to authenticate. The switch cannot provide authentication services to the client through the port. • auto-enables 802.1X authentication and causes the port to begin in the unauthorized state, allowing only EAPOL frames to be sent and received through the port. The authentication process begins when the link state of the port transitions from down to up or when an EAPOL-start frame is received. The switch requests the identity of the client and begins relaying authentication messages between the client and the authentication server. Each client attempting to access the network is uniquely identified by the switch by using the client MAC address. If the client is successfully authenticated (receives an Accept frame from the authentication server), the port state changes to authorized, and all frames from the authenticated client are allowed through the port. If the authentication fails, the port remains in the unauthorized state, but authentication can be retried. If the authentication server cannot be reached, the switch can resend the request. If no response is received from the server after the specified number of attempts, authentication fails, and network access is not granted. When a client logs off, it sends an EAPOL-logoff message, causing the switch port to transition to the unauthorized state. If the link state of a port transitions from up to down, or if an EAPOL-logoff frame is received, the port returns to the unauthorized state. Supported Topologies The 802.1X port-based authentication is supported in two topologies: • Point-to-point • Wireless LAN Catalyst 3560 Switch Software Configuration Guide 9-4 78-16156-01