IFS NS3502-8P-2S User Manual
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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 boot up, 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
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 authentication succeeds or fails. If the
authentication succeeds, the switch port becomes authorized.
The specific exchange of EAP frames depends on the authentication method being used. “
Figure
4-11-2
” shows a message exchange initiated by the client using the One-Time-Password (OTP)
authentication method with a RADIUS server.
