Cisco Systems OL-6415-04 manual Radius Operation, Sequence for EAP Authentication

Chapter 7 Configuring RADIUS Servers

Configuring and Enabling RADIUS

RADIUS Operation

When a wireless user attempts to log in and authenticate to an access point whose access is controlled by a RADIUS server, authentication to the network occurs in the steps shown in Figure 7-1:

Figure 7-1 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	RADIUS Server
or bridge

(relay to server)

4.Authentication challenge (relay to server)

6.Authentication success

(relay to server)

8. Authentication response

(relay to server)	83
	655

In Steps 1 through 9 in Figure 7-1, 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 “Assigning Authentication Types to an SSID” section on page 6-9for instructions on setting up client authentication using a RADIUS server.

Cisco Wireless ISR and HWIC Access Point Configuration Guide

OL-6415-04 7-3