Cisco 802.1X Authentication
This section provides information about 802.1X support on the Cisco Unified IP Phones.
Cisco Unified IP Phones and Cisco Catalyst switches traditionally use Cisco Discovery Protocol (CDP) to identify each other and determine parameters such as VLAN allocation and inline power requirements. CDP does not identify locally attached workstations. Cisco Unified IP Phones provide an EAPOL pass-through mechanism. This mechanism allows a workstation attached to the Cisco Unified 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 Unified 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.
Cisco Unified IP Phones also 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, EAP-TLS, and EAP-MD5 options for network authentication.
Required Network Components
Support for 802.1X authentication on Cisco Unified IP Phones requires several components, including:
Cisco Unified IP Phone: The
phone acts as the 802.1X supplicant, which
initiates the request to access the
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.
Cisco Catalyst Switch (or
other third-party switch): The switch must support 802.1X, so it can act 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.
Best Practices-Requirements and Recommendations
Authentication—If you want to use the
802.1X standard to authenticate Cisco Unified
IP Phones, be sure that you have properly configured the other
components before enabling it on the phone.
Configure PC Port—The 802.1X standard does not take into account
the use of VLANs and thus recommends
that only a single device should authenticate to a specific switch port.
However, some switches (including Cisco
Catalyst switches) support multi-domain authentication. The switch configuration determines if you can connect a
PC to the phone’s PC port.
- Enabled—If you use a switch that supports multidomain authentication, you can enable the PC port and connect a PC to it. In this case, Cisco Unified IP Phones support proxy EAPOL-Logoff to monitor the authentication exchanges between the switch and the attached PC. For more information about IEEE 802.1X support on the Cisco Catalyst switches, see the Cisco Catalyst switch configuration guides at: http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html
- Disabled—If the switch does not support multiple 802.1X-compliant devices on the same port, you should 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 will deny network access to both the phone and the PC.
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 use a switch that supports multidomain authentication, you can continue to use the voice VLAN.
- Disabled—If the switch does not support multidomain authentication, disable the Voice VLAN and consider assigning the port to the native VLAN.
Enter MD5 Shared Secret—If you disable 802.1X authentication or perform
a factory reset on the phone, the
previously configured MD5 shared secret is deleted.