User’s Manual
The specific exchange of EAP frames depends on the authentication method being used. “Figure 4-11-2” shows a message
exchange initiated by the client using the One-Time-Password (OTP) authentication method with a RADIUS server.
Figure 4-11-2: EAP Message Exchange
Ports in Authorized and Unauthorized States
The switch port state determines whether or not the client is granted 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 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
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
retransmit 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.
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