Question

Port security and MAC addresses on managed switch

Asked by: Priest04

How important in real scenario is port security? I have some managed switch and I read in manual that there is an option to limit access to port to certain MAC addresses (you can do this manually, or by learning option). When and why would I use this option? If there is no way to join this network outside the building, would this option remain unused? And If I allow some MAC-A address to access this port, is this the source PC MAC address, or it must contain all the MACs that are in between this switch and a PC? like MAC of some other switch which interconnects these two devices?

Thanks in advance,
Goran

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Asked On
2009-11-03 at 18:53:48ID24869646
Topics

Network Switches & Hubs

,

Network Management

,

Network Security

Participating Experts
3
Points
500
Comments
8

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Answers

 

by: mutahirPosted on 2009-11-03 at 19:17:50ID: 25736104

Switch port security is a good feature if you have tight security policies or are a LAN with critical data

it has to be the client's (PC) network card's mac address, it can be useful as it will not let anyone just plug in their home laptop and get on the network access file resources etc

if you have critical data, financial, it is a good feature to enable as that will make sure only the computers / devices allowed can be plugged in via the network sockets on your business floor ; even if someone gets access to your comms room they won't be able to plug in and get access to the local (Lan).

You can do it by the learning option if your switch has the feature or manually

For manually, you can go into your dhcp server and check for ip addresses and their coresponding mac addresses

http://kl2217.wordpress.com/2009/07/23/basic-switch-security/

 

by: Priest04Posted on 2009-11-03 at 19:43:02ID: 25736208

Thanks for the response. If I have next layout

PC1 --------------------------|
PC2 --------------- some small switch -------------------  managed switch
PC3 --------------------------|


As you can see, 3 PCs through one small switch are connected to one port on main switch. Do I need to enter all 3PCs MAC addresses and MAC address of the intermediate switch to allowed list, or just 3 MAC addresses from PCs?

 

by: guardsman85Posted on 2009-11-03 at 19:46:38ID: 25736224

For networks using port authentication (802.1x), you would also want to use port security for devices which aren't capable of authenticating with the network (printers, scanners, etc.).  Port security is generally considered a relatively poor form of security, as MAC addresses are easily spoofed.  However, it is better than nothing.  If your computers will be moving ports a lot, you'll have to reconfigure the port every time one moves (another reason why many networks use 802.1x instead).

 

by: guardsman85Posted on 2009-11-03 at 19:49:37ID: 25736237

if you're going to be using an intermediary switch, then you might be better just leaving port security off.  it may depend on your model of switch, but most switches will only let you configure one (or maybe two, for a computer and IP phone for instance) address for the port.

 

by: Priest04Posted on 2009-11-04 at 04:33:32ID: 25738638

@guardsman85

After reading about Port authentication (802.1x), I am not sure if we are talking about same thing here? I am not tusing port authentication hereis, at least not in the form of authentication server, this is a sepratae option on a switch. I am not sure about maximimum supported MAC addresses per port, but here is an option called Maximum entries (per port), and it can be set to more than one, so I am guessing that its possible to add more MACs than one. And manual is talking in plural, too.

So, if id it supports more MAC addresses per port, should I always use this option, or not? What is the general rule for administrators?

 

by: donjohnstonPosted on 2009-11-04 at 05:17:52ID: 25738962

>Do I need to enter all 3PCs MAC addresses and MAC address of the intermediate switch to allowed list, or just 3 MAC addresses from PCs?

If the intermediate switch is manageable, then you'll need to add that MAC address. If not, just the 3 PCs MAC addresses.

 

by: guardsman85Posted on 2009-11-04 at 16:21:22ID: 25745646

I believe donjohnston's answer is adequate.   You are correct that port authentication and port security are different.  As to my explanation, i was focusing on answering the "When and why would I use this option?" portion of your question by illustrating when it might be used.

 

by: Priest04Posted on 2009-11-05 at 17:13:27ID: 25755904

Thank you all for the help provided.

20120131-EE-VQP-002

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