IEEE 801.1x Port Based Network Access Control is a standard for authenticating devices at the Data Link Level (Level 2 of the OSI model). When a device is connected to a LAN before it can communicate with other devices on the LAN it must first authenticate itself using the Extensible Authentication Protocol EAP.
If authentication fails, then the device is blocked from using the LAN.

Radius is often used as the Authentication Server.

Recent versions of Windows, Linux, and Mac OS support 802.1x.
802.1x support in VOIP devices is growing.

Resources

• Wikipedia 802.1x article
• Using the 802.1x standard to secure nextgen multimedia VoIP phones - Embedded.com Article
• IEEE 802.1x

See Also

• IEEE