Cisco Systems DL-2159-05 manual Sequence for EAP Authentication

Chapter 8 Security Setup

Security Overview

Figure 8-2 Sequence for EAP Authentication

Wired LAN

Client

device

1.Authentication request

2.Identity request

3.Username

(relay to client)

5.Authentication response (relay to client)

7.Authentication challenge (relay to client)

9.Successful authentication

Access point

or bridge

(relay to server)

4.Authentication challenge (relay to server)

6.Authentication success (relay to server)

8.Authentication response (relay to server)

Server

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In Steps 1 through 9 in Figure 8-2, 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.

There is more than one type of EAP authentication, but the access point behaves the same way for each type: it relays authentication messages from the wireless client device to the RADIUS server and from the RADIUS server to the wireless client device. See the “Setting Up EAP Authentication” section on page 8-15for instructions on setting up EAP on the access point.

Note If you use EAP authentication, you can select open or shared key authentication, but you don’t have to. EAP authentication controls authentication both to your access point and to your network.

Cisco Aironet 1200 Series Access Point Software Configuration Guide

8-4 OL-2159-05