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challenge (EAP-Request/MD5-Challenge) to encrypt the password in the entry. Then, the
server sends the challenge in a RADIUS Access-Challenge packet to the access device.
6. The access device transmits the EAP-Request/MD5-Challenge packet to the client.
7. The client uses the received challenge to encrypt the password, and sends the encrypted
password in an EAP-Response/MD5-Challenge packet to the access device.
8. The access device relays the EAP-Response/MD5-Challenge packet in a RADIUS
Access-Request packet to the authentication server.
9. The authentication server compares the received encrypted password with the encrypted
password it generated at step 5. If the two passwords are identical, the server considers the
client valid and sends a RADIUS Access-Accept packet to the access device.
10. Upon receiving the RADIUS Access-Accept packet, the access device performs the following
operations:
a. Sends an EAP-Success packet to the client.
b. Sets the controlled port in authorized state.
The client can access the network.
11. After the client comes online, the access device periodically sends handshake requests to
check whether the client is still online. By default, if two consecutive handshake attempts fail,
the device logs off the client.
12. Upon receiving a handshake request, the client returns a response. If the client fails to return a
response after a number of consecutive handshake attempts (two by default), the access
device logs off the client. This handshake mechanism enables timely release of the network
resources used by 802.1X users that have abnormally gone offline.
13. The client can also send an EAPOL-Logoff packet to ask the access device for a logoff.
14. In response to the EAPOL-Logoff packet, the access device changes the status of the
controlled port from authorized to unauthorized. Then, the access device sends an EAP-Failure
packet to the client.
EAP termination
Figure 31 shows the basic 802.1X authentication procedure in EAP termination mode, assuming that
CHAP authentication is used.
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