9-5
Catalyst 2928 Switch Software Configuration Guide
OL-23389-01
Chapter 9 Configuring IEEE 802.1x Port-Based Authentication
Understanding IEEE 802.1x Port-Based Authentication
The Termination-Action RADIUS attribute (Attribute [29]) specifies the action to take during
re-authentication. The actions are
Initialize
and
ReAuthenticate
. When the
Initialize
action is set (the
attribute value is
DEFAULT
), the IEEE 802.1x session ends, and connectivity is lost during
re-authentication. When the
ReAuthenticate
action is set (the attribute value is RADIUS-Request),
the session is not affected during re-authentication.
•
You manually re-authenticate the client by entering the
dot1x re-authenticate interface
interface-id
privileged EXEC command.
Authentication Initiation and Message Exchange
During IEEE 802.1x authentication, 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 initiates authentication when the link state changes from down to up or periodically as long as
the port remains up and unauthenticated. The switch sends an EAP-request/identity frame to the client
to request its identity. 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.
Note
If IEEE 802.1x authentication 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 sends 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. For
more information, see the
“Ports in Authorized and Unauthorized States” section on page 9-7
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. If the authentication fails, authentication
can be retried, the port might be assigned to a VLAN that provides limited services, or network access
is not granted. For more information, see the
“Ports in Authorized and Unauthorized States” section on
.
The specific exchange of EAP frames depends on the authentication method being used.
shows a message exchange initiated by the client when the client uses the One-Time-Password (OTP)
authentication method with a RADIUS server.
