Keep in mind that filtering by MAC addresses is not a security measure—someone can easily change the MAC address in your operating system. Do you have a good switch configuration recommendation that you want to share? What other switch topics would you like to see covered in this column? Share your thoughts in this article's discussion.
Want to learn more about router and switch management? Automatically sign up for our free Cisco Routers and Switches newsletter , delivered each Friday! Here are some examples: Editor's Picks. Python is eating the world: How one developer's side project became the hottest programming language on the planet.
- mac os x cursors for xp.
- fleetwood mac stevie nicks dreams lyrics!
- How to trace MAC address | CiscoZine.
- IP phones in Packet Tracer - - The Cisco Learning Network.
- sd gundam online download mac?
- how to download mac app store games for free;
- barcode font for mac word.
How iRobot used data science, cloud, and DevOps to design its next-gen smart home robots. Beyond the PC: Lenovo's ambitious plan for the future of computing. Straight up: How the Kentucky bourbon industry is going high tech. Show Comments. An administrator must re-enable the port manually by issuing the shutdown interface command followed by no shutdown.
This must be done after the offending host has been removed, or the violation will be triggered again as soon as the second host sends another frame.
By changing the violation mode to restrict , we are still alerted when a violation occurs, but legitimate traffic remains unaffected:. Unfortunately, violating traffic will continue to trigger log notifications, and the violation counter will continue to increase, until the violating host is dealt with. By default, port security limits the ingress MAC address count to one. This can be modified, for example, to accommodate both a host and an IP phone connected in series on a switch port:.
An administrator has the option of statically configuring allowed MAC addresses per interface. Obviously, this is not a scalable practice. A much more convenient alternative is to enable "sticky" MAC address learning; MAC addresses will be dynamically learned until the maximum limit for the interface is reached. After a MAC address has been learned, it is recorded to the configuration similarly to as if it were entered manually:.
By default, secure MAC addresses are learned in effect permanently. Aging can be configured so that the addresses expire after a certain amount of time has passed. This allows a new host to take the place of one which has been removed. Aging can be configured to take effect at regular intervals, or only during periods of inactivity.
The following example configures expiration of MAC addresses after five minutes of inactivity:.
Configure static MAC address
At this point, the old address will be re-learned the next time a frame is sent from that host, or a new host can take its place. To avoid having to manually intervene every time a port-security violation forces an interface into the error-disabled state, one can enable auto-recovery for port security violations. A recovery interval is configured in seconds. Ten minutes after a port was error-disabled, we can see that the port is automatically transitioned back into operation:.
This is a great way to automatically clear port security violations after the user has been given an opportunity to remove the offending host s. Note that is the cause is not cleared, the violation will trigger again after the port comes back up, re-initating the auto-recovery cycle. Although a deterrent, port security is not a reliable security feature, as MAC addresses are trivially spoofed, and multiple hosts can still easily be hidden behind a small router. IEEE Posted in Security , Switching. I actually had to learn his the other day. We had enabled all user facing ports on our G's using the Catalyst Web Interface, configuring them as "Desktop" ports.
As a result, when a rogue switch is connected, the port was shutdown permanently and a manual "shut" and "no shut" would be needed each time an offense occurred. Only glanced over the article, but port-security is definitely a cool feature to have in smaller to medium sized enviroments, good for preventing mac-address-table flooding attacks where a user may attempt to take advantage of a full mac table and sniffing those unknown unicast frames that will get flooded once the switch can no longer learn additional mac addresses.
Talk about just in time.
Tweaking Port Security
I was needing to implement some of these features this week. Thanks for the write up. Something to keep in mind: some protocols, e. The switch port where the routers are connected will see two separate mac address from that port. If the port is set to MAX 1 then the port will err-disable.
Share on LinkedIn Share.
Problem with IP Telephony Setup with Packet Tracer | Network Infrastructure Forums
Share on Digg Share. In Cisco technology, the traceroute mac command output shows the Layer2 path when the specified source and destination addresses belong to the same VLAN.
- How to trace MAC address.
- smb mac os x yosemite.
- coupon code for mac photo book.
Fabio Semperboni. Join us on LinkedIn! Join us on Facebbook! Follow Us on Twitter! Subscribe to our RSS Feed! Join us on Youtube!