76
Packet exchange
method
Benefits Limitations
The processing is complex on the
access device.
EAP relay
Figure 30 shows the basic 802.1X authentication procedure in EAP relay mode, assuming that
EAP-MD5 is used.
Figure 30 802.1X authentication procedure in EAP relay mode
The following steps describe the 802.1X authentication procedure:
1. When a user launches the 802.1X client and enters a registered username and password, the
802.1X client sends an EAPOL-Start packet to the access device.
2. The access device responds with an EAP-Request/Identity packet to ask for the client
username.
3. In response to the EAP-Request/Identity packet, the client sends the username in an
EAP-Response/Identity packet to the access device.
4. The access device relays the EAP-Response/Identity packet in a RADIUS Access-Request
packet to the authentication server.
5. The authentication server uses the identity information in the RADIUS Access-Request to
search its user database. If a matching entry is found, the server uses a randomly generated
EAPOL
EAPOR
(1) EAPOL-Start
(2) EAP-Request/Identity
(3) EAP-Response/Identity
(6) EAP-Request/MD5-Challenge
(10) EAP-Success
(7) EAP-Response/MD5-Challenge
(4) RADIUS Access-Request
(EAP-Response/Identity)
(5) RADIUS Access-Challenge
(EAP-Request/MD5-Challenge)
(9) RADIUS Access-Accept
(EAP-Success)
(8) RADIUS Access-Request
(EAP-Response/MD5-Challenge)
(11) EAP-Request/Identity
(12) EAP-Response/Identity
(13) EAPOL-Logoff
...
Client Device Authentication server
Port authorized
Port unauthorized
(14) EAP-Failure
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