Cisco Systems EAP Authentication to the Network

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Cisco IOS Software Configuration Guide for Cisco Aironet Access Points
OL-29225-01
Chapter11 Configuring Authentication Types
Understanding Authentication Types
EAP Authentication to the Network
This authentication type provides the highest level of security for your wireless network. By using the
Extensible Authentication Protocol (EAP) to interact with an EAP-compatible RADIUS server, the
access point helps a wireless client device and the RADIUS server to perform mutual authentication and
derive a dynamic unicast WEP key. The RADIUS server sends the WEP key to the access point, which
uses it for all unicast data signals that it sends to or receives from the client. The access point also
encrypts its broadcast WEP key (entered in the access point’s WEP key slot 1) with the client’s unicast
key and sends it to the client.
When you enable EAP on your access points and client devices, authentication to the network occurs in
the sequence shown in Figure 11-3:
Figure11-3 Sequence for EAP Authentication
In Steps 1 through 9 in Figure11-3, a wireless client device and a RADIUS server on the wired LAN
use 802.1x and EAP to perform a mutual authentication through the access point. The RADIUS server
sends an authentication challenge to the client. The client uses a one-way encryption of the user-supplied
password to generate a response to the challenge and sends that response to the RADIUS server. Using
information from its user database, the RADIUS server creates its own response and compares that to
the response from the client. When the RADIUS server authenticates the client, the process repeats in
reverse, and the client authenticates the RADIUS server.
When mutual authentication is complete, the RADIUS server and the client determine a WEP key that
is unique to the client and provides the client with the appropriate level of network access, thereby
approximating the level of security in a wired switched segment to an individual desktop. The client
loads this key and prepares to use it for the logon session.
During the logon session, the RADIUS server encrypts and sends the WEP key, called a session key, over
the wired LAN to the access point. The access point encrypts its broadcast key with the session key and
sends the encrypted broadcast key to the client, which uses the session key to decrypt it. The client and
access point activate WEP and use the session and broadcast WEP keys for all communications during
the remainder of the session.
Access point
or bridge
Wired LAN
Client
device RADIUS Server
1. Authentication request
2. Identity request
3. Username
(relay to client)
(relay to server)
4. Authentication challenge
5. Authentication response
(relay to client)
(relay to server)
6. Authentication success
7. Authentication challenge
(relay to client)
(relay to server)
8. Authentication response
9. Successful authentication (relay to server)
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