ZyXEL Communications Prestige 2802HW(L)-IX Support Notes page 81

Prestige 2802HW(L)-Ix Support Notes
The EAP protocol can support multiple authentication mechanisms, such as MD5-challenge, One-Time
Passwords, Generic Token Card, TLS and TTLS etc. Typically, the authenticator will send an initial Identity
Request followed by one or more Requests for authentication information. When supplicant receive the EAP
request, it will reply associated EAP response. So far, ZyXEL Wireless AP only supports MD-5 challenge
authentication mechanism, but will support TLS and TTLS in the future.
EAPOL Exchange between 802.1x Authenticator and Supplicant
The authenticator or the supplicant can initiate authentication. If you enable 802.1x authentication on the
Wireless AP, the authenticator must initiate authentication when it determines that the Wireless link state
transitions from down to up. It then sends an EAP-request/identity frame to the 802.1x client to request its
identity (typically, the authenticator sends an initial identity/request frame followed by one or more requests for
authentication information). Upon receipt of the frame, the supplicant responds with an EAP-response/identity
frame.
However, if during bootup, the supplicant does not receive an EAP-request/identity frame from the Wireless AP,
the client can initiate authentication by sending an EAPOL-Start frame, which prompts the switch to request the
supplicant＇s identity. In above case, authenticator co-locate with authentication server. When the supplicant
supplies its identity, the authenticator directly exchanges EAPOL to the supplicant until authentication succeeds
or fails. If the authentication succeeds, the port becomes authorized. If the authentication fails, the port becomes
unauthorized. When the supplicant does not need Wireless access any more, it sends EAPOL-Logoff packet to
terminate its 802.1x session, the port state will become unauthorized. The following figure shows the EAPOL
exchange ping-pong chart.
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