GE -DSH-73 User Manual page 124

Chapter 5: Web-Based Management
the client. In this release, the Remote Authentication Dial-In User Service (RADIUS)
security system with Extensible Authentication Protocol (EAP) extensions is the
only supported authentication server; it is available in Cisco Secure Access Control
Server version 3.0. RADIUS operates in a client/server model in which secure
authentication information is exchanged between the RADIUS server and one or
more RADIUS clients.
• Switch (802.1X device)-controls the physical access to the network based on the
authentication status of the client. The switch acts as an intermediary (proxy)
between the client and the authentication server, requesting identity information
from the client, verifying that information with the authentication server, and
relaying a response to the client. The switch includes the RADIUS client, which is
responsible for encapsulating and decapsulating the Extensible Authentication
Protocol (EAP) frames and interacting with the authentication server. When the
switch receives EAPOL frames and relays them to the authentication server, the
Ethernet header is stripped and the remaining EAP frame is re-encapsulated in
the RADIUS format. The EAP frames are not modified or examined during
encapsulation, and the authentication server must support EAP within the native
frame format. When the switch receives frames from the authentication server,
the server's frame header is removed, leaving the EAP frame, which is then
encapsulated for Ethernet and sent to the client.
• Authentication Initiation and Message Exchange
The switch or the client can initiate authentication. If you enable authentication
on a port by using the dot1x port-control auto interface configuration command,
the switch must initiate authentication when it determines that the port link state
transitions from down to up. It then sends an EAP-request/identity frame to the
client to request its identity (typically, the switch sends an initial identity/request
frame followed by one or more requests for authentication information). Upon
receipt of the frame, the client responds with an EAP-response/identity frame.
However, if during bootup, the client does not receive an EAP-request/identity
frame from the switch, the client can initiate authentication by sending an EAPOL-
start frame, which prompts the switch to request the client's identity
NOTE: If 802.1X is not enabled or supported on the network access device, any EAPOL
frames from the client are dropped. If the client does not receive an EAP-
request/identity frame after three attempts to start authentication, the client
transmits frames as if the port is in the authorized state. A port in the authorized state
effectively means that the client has been successfully authenticated.
When the client supplies its identity, the switch begins its role as the intermediary,
passing EAP frames between the client and the authentication server until
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