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Catalyst 2928 Switch Software Configuration Guide
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Chapter 9 Configuring IEEE 802.1x Port-Based Authentication
Understanding IEEE 802.1x Port-Based Authentication
If the security violation is caused by the first authenticated host, the port becomes error-disabled and
immediately shuts down.
The port security violation modes determine the action for security violations. For more
information, see the
“Security Violations” section on page 22-10
.
•
When you manually remove an IEEE 802.1x client address from the port security table by using the
no switchport port-security mac-address
mac-address
interface configuration command, you
should re-authenticate the IEEE 802.1x client by using the
dot1x re-authenticate interface
interface-id
privileged EXEC command.
•
When an IEEE 802.1x client logs off, the port changes to an unauthenticated state, and all dynamic
entries in the secure host table are cleared, including the entry for the client. Normal authentication
then takes place.
•
If the port is administratively shut down, the port becomes unauthenticated, and all dynamic entries
are removed from the secure host table.
•
Port security and a voice VLAN can be configured simultaneously on an IEEE 802.1x port that is in
either single-host or multiple-hosts mode. Port security applies to both the voice VLAN identifier
(VVID) and the port VLAN identifier (PVID).
For more information about enabling port security on your switch, see the
Using IEEE 802.1x Authentication with MAC Authentication Bypass
You can configure the switch to authorize clients based on the client MAC address (see
) by using the MAC authentication bypass feature. For example, you can enable this feature on
IEEE 802.1x ports connected to devices such as printers.
If IEEE 802.1x authentication times out while waiting for an EAPOL response from the client, the switch
tries to authorize the client by using MAC authentication bypass.
When the MAC authentication bypass feature is enabled on an IEEE 802.1x port, the switch uses the
MAC address as the client identity. The authentication server has a database of client MAC addresses
that are allowed network access. After detecting a client on an IEEE 802.1x port, the switch waits for an
Ethernet packet from the client. The switch sends the authentication server a RADIUS-access/request
frame with a username and password based on the MAC address. If authorization succeeds, the switch
grants the client access to the network. If authorization fails, the switch assigns the port to the guest
VLAN if one is configured.
If an EAPOL packet is detected on the interface during the lifetime of the link, the switch determines
that the device connected to that interface is an IEEE 802.1x-capable supplicant and uses IEEE 802.1x
authentication (not MAC authentication bypass) to authorize the interface. EAPOL history is cleared if
the interface link status goes down.
If the switch already authorized a port by using MAC authentication bypass and detects an IEEE 802.1x
supplicant, the switch does not unauthorize the client connected to the port. When re-authentication
occurs, the switch uses IEEE 802.1x authentication as the preferred re-authentication process if the
previous session ended because the Termination-Action RADIUS attribute value is DEFAULT.
Clients that were authorized with MAC authentication bypass can be re-authenticated. The
re-authentication process is the same as that for clients that were authenticated with IEEE 802.1x.
During re-authentication, the port remains in the previously assigned VLAN. If re-authentication is
successful, the switch keeps the port in the same VLAN. If re-authentication fails, the switch assigns the
port to the guest VLAN, if one is configured.
