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Chapter 8
Configuring IEEE 802.1x Port-Based Authentication
When you configure a port as unidirectional by using the dot1x control-direction in interface
configuration command, the port changes to the spanning-tree forwarding state. The port can send
packets to the host but cannot receive packets from the host.
When you configure a port as bidirectional by using the dot1x control-direction both interface
configuration command, the port is access-controlled in both directions. The port does not receive
packets from or send packets to the host.
Using IEEE 802.1x Authentication with MAC Authentication Bypass
You can configure the switch to authorize clients based on the client MAC address (see
page
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.
If re-authentication is based on the Session-Timeout RADIUS attribute (Attribute[27]) and the
Termination-Action RADIUS attribute (Attribute [29]) and if the Termination-Action RADIUS attribute
(Attribute [29]) action is Initialize, (the attribute value is DEFAULT), the MAC authentication bypass
session ends, and connectivity is lost during re-authentication. If MAC authentication bypass is enabled
and the IEEE 802.1x authentication times out, the switch uses the MAC authentication bypass feature to
initiate re-authorization. For more information about these AV pairs, see RFC 3580, "IEEE 802.1X
Remote Authentication Dial In User Service (RADIUS) Usage Guidelines."
MAC authentication bypass interacts with the features:
•
•
OL-8915-03
8-4) by using the MAC authentication bypass feature. For example, you can enable this feature on
IEEE 802.1x authentication—You can enable MAC authentication bypass only if IEEE 802.1x
authentication is enabled on the port.
Guest VLAN—If a client has an invalid MAC address identity, the switch assigns the client to a
guest VLAN if one is configured.
Understanding IEEE 802.1x Port-Based Authentication
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
Figure 8-2 on
8-17
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