When you work with the Cisco Switches you can enable a function called port security.  Port Security is nice because you can limit the number of MAC addresses that can be learned and can pass traffic on a single port of a switch.  For example if you have a PC at a KIOSK and that is the only PC that should EVER be connected to switchport f0/5 you could accomplish this with port security.

Here is a sample of a port security configuration and a brief explanation of what it does.  Keep in mind that there is more to it than just this configuration but this should get you through the CCNA.

! Begin by entering the interface you want to configure port security on.

SwitchX(config)#interface fa0/5

! Next set the port as a static access port.  
! This must be done before enabling port security.

SwitchX(config-if)#switchport mode access

! Next Enable Port Security

SwitchX(config-if)#switchport port-security

! Next Set the Maximum number of MAC addresses to be seen, 
! or allowed on this port.

SwitchX(config-if)#switchport port-security maximum 1

! Next configure "Sticky MAC Address Learning" In essence this says
! to take the first MAC address I see and make it a permanent MAC address.

SwitchX(config-if)#switchport port-security mac-address sticky

! Finally set the action to happen if a violation occurs.  
! In this case the port will be shutdown,
! or end up in a state of ERR-Disable. 
! You can verify this with a Show Interface.
 
SwitchX(config-if)#switchport port-security violation shutdown

More Information on Port Security can be found here on the Cisco Web Site.

If you found this post helpful why not leave a comment? Also, dont forget to subscribe to our feed.

PS: Welcome StumbleUpon Readers! 

This post has gained some momentum lately and for those of you arriving here from Stumble, why not subscribe to our feed.  Why subscribe?

• Contests Every Other Month
• Loads of posts
• Answers to questions you need answers for.

Thats right!  This blog is for you!  How can we help?