The switchport port-security command is an interface configuration command used on a Catalyst 2950 series switch to enable basic port security on the interface. The syntax of the command is as follows:
switch(config-if)#switchport port-security
Switchport security can be used to:
* Limit the computers that are allowed to connect to the LAN (by specifying the MAC addresses allowed on the port)
* Limit the number of MAC address allowed to be accessing a port
* Set the action the port will take when a violation of the security rule occurs

The set port-security, set port-security enable, and switchport port-security enable commands are incorrect because these are not valid Cisco IOS commands.