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Cisco Catalyst Blade Switch 3120 for HP Software Configuration Guide
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Chapter 9 Configuring IEEE 802.1x Port-Based Authentication
Understanding IEEE 802.1x Port-Based Authentication
In single-host mode, only the IP phone is allowed on the voice VLAN. In multiple-hosts mode,
additional clients can send traffic on the voice VLAN after a supplicant is authenticated on the PVID.
When multiple-hosts mode is enabled, the supplicant authentication affects both the PVID and the
VVID.
A voice VLAN port becomes active when there is a link, and the device MAC address appears after the
first CDP message from the IP phone. Cisco IP phones do not relay CDP messages from other devices.
As a result, if several IP phones are connected in series, the switch recognizes only the one directly
connected to it. When IEEE 802.1x authentication is enabled on a voice VLAN port, the switch drops
packets from unrecognized IP phones more than one hop away.
When IEEE 802.1x authentication is enabled on a port, you cannot configure a port VLAN that is equal
to a voice VLAN.
Note
If you enable IEEE 802.1x authentication on an access port on which a voice VLAN is configured and
to which a Cisco IP Phone is connected, the Cisco IP phone loses connectivity to the switch for up to 30
seconds.
For more information about voice VLANs, see
Chapter 14, “Configuring Voice VLAN.”
Using IEEE 802.1x Authentication with Port Security
You can configure an IEEE 802.1x port with port security in either single-host or multiple-hosts mode.
(You also must configure port security on the port by using the switchport port-security interface
configuration command.) When you enable port security and IEEE 802.1x authentication on a port, IEEE
802.1x authentication authenticates the port, and port security manages network access for all MAC
addresses, including that of the client. You can then limit the number or group of clients that can access
the network through an IEEE 802.1x port.
These are some examples of the interaction between IEEE 802.1x authentication and port security on the
switch:
•
When a client is authenticated, and the port security table is not full, the client MAC address is added
to the port security list of secure hosts. The port then proceeds to come up normally.
When a client is authenticated and manually configured for port security, it is guaranteed an entry
in the secure host table (unless port security static aging has been enabled).
A security violation occurs if the client is authenticated, but the port security table is full. This can
happen if the maximum number of secure hosts has been statically configured or if the client ages
out of the secure host table. If the client address is aged, its place in the secure host table can be
taken by another host.
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 25-9
.
•
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.
