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 switch port, you can configure an access port VLAN that
is also a voice VLAN.
When IP phones are connected to an 802.1x-enabled switch port that is in single host mode, the switch grants
the phones network access without authenticating them. We recommend that you use multidomain authentication
(MDA) on the port to authenticate both a data device and a voice device, such as an IP phone
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.
Note
IEEE 802.1x Authentication with Port Security
In general, Cisco does not recommend enabling port security when IEEE 802.1x is enabled. Since IEEE 802.1x
enforces a single MAC address per port (or per VLAN when MDA is configured for IP telephony), port
security is redundant and in some cases may interfere with expected IEEE 802.1x operations.
IEEE 802.1x Authentication with Wake-on-LAN
The IEEE 802.1x authentication with wake-on-LAN (WoL) feature allows dormant PCs to be powered when
the switch receives a specific Ethernet frame, known as the
magic packet
. You can use this feature in
environments where administrators need to connect to systems that have been powered down.
When a host that uses WoL is attached through an IEEE 802.1x port and the host powers off, the IEEE 802.1x
port becomes unauthorized. The port can only receive and send EAPOL packets, and WoL magic packets
cannot reach the host. When the PC is powered off, it is not authorized, and the switch port is not opened.
When the switch uses IEEE 802.1x authentication with WoL, the switch forwards traffic to unauthorized
IEEE 802.1x ports, including magic packets. While the port is unauthorized, the switch continues to block
ingress traffic other than EAPOL packets. The host can receive packets but cannot send packets to other
devices in the network.
If PortFast is not enabled on the port, the port is forced to the bidirectional state.
Note
When you configure a port as unidirectional by using the
authentication 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
authentication 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.
Catalyst 2960-X Switch Security Configuration Guide, Cisco IOS Release 15.0(2)EX
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Configuring IEEE 802.1x Port-Based Authentication
IEEE 802.1x Authentication with Port Security