Protected ports

The basic security feature available in a switch.

The protected ports are used for isolating ports within same vlan and this work within a single switch. 

For example if a switch has 3 ports i.e fa0/0, fa0/1 and fa1/1, all in a same vlan 100. If "switchport protected" command is configured in fa0/0 and fa0/1 that means host on f0/0 and host on f0/1 can not send frames to each other while both hosts on fa0/0 and fa0/1 can still send and receive frames to or from  host on fa1/1. 

Configuration on switch ports fa0/0 and fa0/1

#interface range fa0/0 , fa0/1

#switchport access vlan 100

#switchport protected

Configuration on switch port fa1/1

#interface fa1/1
#switchport access vlan 100