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(8) The supplicant system can also terminate the authenticated state by sending
EAPOL-Logoff packets to the switch. The switch then changes the port state from
accepted to rejected.
2. EAP Terminating Mode
In this mode, packet transmission is terminated at authenticator systems and the EAP packets
are mapped into RADIUS packets. Authentication and accounting are accomplished through
RADIUS protocol.
In this mode, PAP or CHAP is employed between the switch and the RADIUS server. This switch
supports the PAP terminating mode. The authentication procedure of PAP is illustrated in the
following figure.
Figure 12-21 PAP Authentication Procedure
In PAP mode, the switch encrypts the password and sends the user name, the
randomly-generated key, and the supplicant system-encrypted password to the RADIUS
server for further authentication. Whereas the randomly-generated key in EAP-MD5 relay
mode is generated by the authentication server, and the switch is responsible to encapsulate
the authentication packet and forward it to the RADIUS server.
802.1X Timer
In 802.1 x authentication, the following timers are used to ensure that the supplicant system,
the switch, and the RADIUS server interact in an orderly way:
1. Supplicant system timer (Supplicant Timeout): This timer is triggered by the switch
after the switch sends a request packet to a supplicant system. The switch will resend
the request packet to the supplicant system if the supplicant system fails to respond in
the specified timeout period.
2. RADIUS server timer (Server Timeout): This timer is triggered by the switch after the
switch sends an authentication request packet to RADIUS server. The switch will resend
the authentication request packet if the RADIUS server fails to respond in the specified
timeout period.
3. Quiet-period timer (Quiet Period): This timer sets the quiet-period. When a supplicant
system fails to pass the authentication, the switch quiets for the specified period before
it processes another authentication request re-initiated by the supplicant system.
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