Cisco 8800 Series Manual page 154

802.1X Authentication
Cisco IP Phones provide an EAPOL pass-through mechanism. This mechanism allows a workstation attached
to the Cisco IP Phone to pass EAPOL messages to the 802.1X authenticator at the LAN switch. The
pass-through mechanism ensures that the IP phone does not act as the LAN switch to authenticate a data
endpoint before accessing the network.
Cisco IP Phones also provide a proxy EAPOL Logoff mechanism. In the event that the locally attached PC
disconnects from the IP phone, the LAN switch does not see the physical link fail, because the link between
the LAN switch and the IP phone is maintained. To avoid compromising network integrity, the IP phone sends
an EAPOL-Logoff message to the switch on behalf of the downstream PC, which triggers the LAN switch to
clear the authentication entry for the downstream PC.
Support for 802.1X authentication requires several components:
• Cisco IP Phone: The phone initiates the request to access the network. Cisco IP Phones contain an 802.1X
supplicant. This supplicant allows network administrators to control the connectivity of IP phones to the
LAN switch ports. The current release of the phone 802.1X supplicant uses the EAP-FAST and EAP-TLS
options for network authentication.
• Cisco Secure Access Control Server (ACS) (or other third-party authentication server): The authentication
server and the phone must both be configured with a shared secret that authenticates the phone.
• A LAN switch supporting 802.1X: The switch acts as the authenticator and pass the messages between
the phone and the authentication server. After the exchange completes, the switch grants or denies the
phone access to the network.
You must perform the following actions to configure 802.1X.
• Configure the other components before you enable 802.1X Authentication on the phone.
• Configure PC Port: The 802.1X standard does not consider VLANs and thus recommends that only a
single device should be authenticated to a specific switch port. However, some switches support
multidomain authentication. The switch configuration determines whether you can connect a PC to the
PC port of the phone.
• Yes: If you are using a switch that supports multidomain authentication, you can enable the PC port
• No: If the switch does not support multiple 802.1X-compliant devices on the same port, you should
• Configure Voice VLAN: Because the 802.1X standard does not account for VLANs, you should configure
this setting based on the switch support.
• Enabled: If you are using a switch that supports multidomain authentication, you can continue to
• Disabled: If the switch does not support multidomain authentication, disable the Voice VLAN and
Cisco IP Phone 8800 Series Multiplatform Phone Administration Guide for Release 11.3(1) and Later
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and connect a PC to it. In this case, Cisco IP Phones support proxy EAPOL-Logoff to monitor the
authentication exchanges between the switch and the attached PC.
disable the PC Port when 802.1X authentication is enabled. If you do not disable this port and
subsequently attempt to attach a PC to it, the switch denies network access to both the phone and
the PC.
use the voice VLAN.
consider assigning the port to the native VLAN.
Cisco IP Phone Configuration