Appendix C --- IEEE 802.1x protocol over IP DSLAM

Understanding How 802.1X Authentication Works

IEEE 802.1X is a client-server-based access control and authentication protocol that restricts unauthorized devices from connecting to a local area network (LAN) through publicly accessible ports. 802.1X authenticates each user device that is connected to a switch port before making available any services that are offered by the switch or the LAN. Until the device is authenticated, 802.1X access control allows only Extensible Authentication Protocol over LAN (EAPOL) traffic through the port to which the device is connected. After authentication is successful, normal traffic can pass through the port.

802.1X controls network access by creating two distinct virtual access points at each port (See Above Figure). One access point is an uncontrolled port; the other is a controlled port. All traffic through the single port is available to both access points. Only EAPOL traffic is allowed to pass through the uncontrolled port, which is always open. The controlled port is open only when the device that is connected to the port has been authorized by 802.1X. After this authorization takes place, the controlled port opens, allowing normal traffic to pass.

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