Cisco Catalyst 3550 Series User Manual

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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter9 Configuring 802.1X Port-Based Authentication
Understanding 802.1X Port-Based Authentication
• Port security and a voice VLAN can be configured simultaneously on an 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).
• When an 802.1X client address is manually removed from the port security table, we recommend
that you re-authenticate the client by entering the dot1x re-authenticate privileged EXEC
command.
For more information about enabling port security on your switch, see the “Configuring Port Security”
section on page 21-8.
Using 802.1X with Voice VLAN Ports
A voice VLAN port is a special access port associated with two VLAN identifiers:
• VVID to carry voice traffic to and from the IP phone. The VVID is used to configure the IP phone
connected to the port.
• PVID to carry the data traffic to and from the workstation connected to the switch through the IP
phone. The PVID is the native VLAN of the port.
Each port that you configure for a voice VLAN is associated with a PVID and a VVID. This
configuration allows voice traffic and data traffic to be separated onto different VLANs.
When you enable the single-host mode, only one 802.1X client is allowed on the primary VLAN; other
workstations are blocked. When you enable the multiple-hosts mode and an 802.1X client is
authenticated on the primary VLAN, additional clients on the voice VLAN are unrestricted after 802.1X
authentication succeeds on the primary VLAN.
A voice VLAN port becomes active when there is 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 Cisco IP phones are connected in series, the switch recognizes only the one directly
connected to it. When 802.1X is enabled on a voice VLAN port, the switch drops packets from
unrecognized Cisco IP phones more than one hop away.
When 802.1X is enabled on a port, you cannot configure a port VLAN that is equal to a voice VLAN.
For more information about voice VLANs, see Chapter 14, “Configuring Voice VLAN.”
Using 802.1X with VLAN Assignment
You can limit network access for certain users by using VLAN assignment. After successful 802.1X
authentication of a port, the RADIUS server sends the VLAN assignment to configure the switch port.
The RADIUS server database maintains the username-to-VLAN mappings, which assigns the VLAN
based on the username of the client connected to the switch port.
When configured on the switch and the RADIUS server, 802.1X with VLAN assignment has these
characteristics:
• If no VLAN is supplied by the RADIUS server or if 802.1X authorization is disabled, the port is
configured in its access VLAN after successful authentication.
• If 802.1X authorization is enabled but the VLAN information from the RADIUS server is not valid,
the port returns to the unauthorized state and remains in the configured access VLAN. This prevents
ports from appearing unexpectedly in an inappropriate VLAN because of a configuration error.
Configuration errors could include a VLAN specified for a routed port, a malformed VLAN ID, a
nonexistent or internal (routed port) VLAN ID, or attempted assignment to a voice VLAN ID.

Cisco Catalyst 3550 Series Specifications

General

Brand	Cisco
Model	Catalyst 3550 Series
Category	Network Router
Language	English