Cisco WS-C2960-24LC-S Software Configuration Manual page 190

Understanding IEEE 802.1x Port-Based Authentication
When configured on the switch and the RADIUS server, IEEE 802.1x authentication with VLAN
assignment has these characteristics:
If no VLAN is supplied by the RADIUS server or if IEEE 802.1x authentication is disabled, the port
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is configured in its access VLAN after successful authentication. Recall that an access VLAN is a
VLAN assigned to an access port. All packets sent from or received on this port belong to this
VLAN.
If IEEE 802.1x authentication is enabled but the VLAN information from the RADIUS server is not
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valid, authorization fails and configured VLAN remains in use. This prevents ports from appearing
unexpectedly in an inappropriate VLAN because of a configuration error.
Configuration errors could include specifying a VLAN for a routed port, a malformed VLAN ID, a
nonexistent or internal (routed port) VLAN ID, an RSPAN VLAN, a shut down or suspended VLAN. In
the case of a mutlidomain host port, configuration errors can also be due to an attempted assignment of
a data VLAN that matches the configured or assigned voice VLAN ID (or the reverse).
If IEEE 802.1x authentication is enabled and all information from the RADIUS server is valid, the
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authorized device is placed in the specified VLAN after authentication.
• If the multiple-hosts mode is enabled on an IEEE 802.1x port, all hosts are placed in the same VLAN
(specified by the RADIUS server) as the first authenticated host.
• Enabling port security does not impact the RADIUS server-assigned VLAN behavior.
• If IEEE 802.1x authentication is disabled on the port, it is returned to the configured access VLAN
and configured voice VLAN.
• If an IEEE 802.1x port is authenticated and put in the RADIUS server-assigned VLAN, any change
to the port access VLAN configuration does not take effect. In the case of a multidomain host, the
same applies to voice devices when the port is fully authorized with these exceptions:
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When the port is in the force authorized, force unauthorized, unauthorized, or shutdown state, it is put
into the configured access VLAN.
The IEEE 802.1x authentication with VLAN assignment feature is not supported on trunk ports, dynamic
ports, or with dynamic-access port assignment through a VLAN Membership Policy Server (VMPS).
To configure VLAN assignment you need to perform these tasks:
Enable AAA authorization by using the network keyword to allow interface configuration from the
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RADIUS server.
Enable IEEE 802.1x authentication. (The VLAN assignment feature is automatically enabled when
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you configure IEEE 802.1x authentication on an access port).
Catalyst 2960 Switch Software Configuration Guide
9-10
If the VLAN configuration change of one device results in matching the other device configured
or assigned VLAN, then authorization of all devices on the port is terminated and multidomain
host mode is disabled until a valid configuration is restored where data and voice device
configured VLANs no longer match.
If a voice device is authorized and is using a downloaded voice VLAN, the removal of the voice
VLAN configuration, or modifying the configuration value to dot1p or untagged results in voice
device un-authorization and the disablement of multi-domain host mode.
Chapter 9 Configuring IEEE 802.1x Port-Based Authentication
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