Cisco: Configure a Switch's Interface to Use 802.1x Authentication

Here are the Cisco command lines to enable a switch's interface to use 802.1x authentication:

Switch# configure terminal
Switch(config)# aaa new-model
Switch(config)# aaa authentication dot1x default group radius
Switch(config)# interface fastethernet0/1
Switch(config-if)# dot1x port-control auto
Switch(config-if)# end

Reference:
Configuring 802.1X Port-Based Authentication
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2950/software/release/12-1_9_ea1/configuration/guide/scg/Sw8021x.html