What is a Managed Switch?

A managed switch allows you to control the individual ports of your switch. Features of course vary with manufacturers and models, but even the most basic will have the ability to turn the port on or off and control its link speed and duplex settings. That control is for security; it prevents someone just walking in and connecting to your lan through an unused port.

Beyond that, you might be able to specify a particular MAC address that is allowed to connect. That prevents someone from replacing machines with their own. You might be able to set login authentication, also. You may be able to designate certain ports as "high priority"; for example the ports your servers are on. Setting bandwidth limits, monitoring port traffic and of course logging are also features.

VLANS (Virtual LANS) are a popular option. This allows you to set a broadcast domain on certain ports, so that broadcast traffic isn't passed on to the other ports. This can also isolate machines from each other for security purposes.

Link aggregation ties together multiple ports, allowing two switches to be connected more than once for higher throughput between them. The switch may support Spanning Tree, which lets you have multiple paths for redundancy without having to worry about looping.

These switches may also have snmp agents that will report status to snmp monitors. Nowadays they usually have a web interface for configuration in addition to the traditional command line method. Older models might require access through a serial console, but more recent devices will have the web interface.

19 comments

More Articles by Tony Lawrence - Find me on Google+

Click here to add your comments




Fri Jan 23 09:20:57 2009:   amith


This artical is very good.. I want to know how spanning tree is used in managed switches? Can anyone answer.. please..





Fri Jan 23 12:37:06 2009:   TonyLawrence


That could be an article by itself. Spanning tree simply prevents loops when you have multiple switches wired together in a way that otherwise could loop back. Do a Google search if you want to find articles that explain how it works in practice,

This site deals with small business - I seldom am working with anyone large enough to even need such things; many of my customers get by with a single switch :-)

Still, these kind of features are appearing in lower priced equipment.. I imagine it might eventually show up in the $50 units my customers are more likely to own.



Tue Nov 10 06:23:57 2009:   santoshchauhan


this is a nice article but not so good for begener it's just need more clearence. thank u



Tue Nov 10 12:02:11 2009:   TonyLawrence


Tell me what confuses you and I'll try to help.



Tue Feb 2 02:23:48 2010:   ChadSpaltro


I've been looking for information that simply explains the difference between managed and unmanaged switches. Your article gave me a good head start. From what I've read on other sites, an unmanaged switch is really a hub, or could have some segregation built in but offers no way to program or setup how it works... is that correct?



Tue Feb 2 02:39:17 2010:   TonyLawrence


No. A switch is not a hub.

On a hub, every port sees all traffic. On a switch, once it learns that a particular ip address is on port 6, that's the only place traffic (except broadcasts) for that ip goes.



Tue Feb 2 02:40:57 2010:   TonyLawrence


For more on switches and hubs. see http://aplawrence.com/Lighter/routers-switches-hubs.html



Tue Feb 2 15:25:12 2010:   BigDumbDInosaur
http://bcstechnology.net

On a hub, every port sees all traffic. On a switch, once it learns that a particular ip address is on port 6, that's the only place traffic (except broadcasts) for that ip goes.

Actually, the switch learns about MAC addresses. Although IP is the dominant system at this point in time, one could theoretically use a switch in an older Novell network where IPX is used.



Tue Feb 2 15:29:46 2010:   TonyLawrence


Yes. Though for this person, I didn't want to complicate his understanding.



Fri Feb 12 18:06:33 2010:   anonymous


do managed switched have the ability to push dhcp to a group of ports? we have an all static ip network here, however, we have a need for dchp in a very small way. can i do this without purchasing another router?



Fri Feb 12 18:14:41 2010:   TonyLawrence


A DHCP request is a broadcast - ANY switch passes broadcasts to all ports by default.



Fri Feb 12 18:15:54 2010:   TonyLawrence


But if you are asking if a managed switch has DHCP server abilities, no.



Fri Feb 12 18:27:49 2010:   anonymous


thats what i was asking. thanks for the reply



Fri Feb 12 18:34:14 2010:   BigDumbDinosaur
http://bcstechnology.net

do managed switched have the ability to push dhcp to a group of ports? we have an all static ip network here, however, we have a need for dchp in a very small way. can i do this without purchasing another router?

You need either a router or a computer to respond to DHCP requests. If you have a server attached to your network it can take care of this for you. If not, an inexpensive router can do the job (3Com's office-connect series is good).

I'm hoping for your sake that you are not on a Windows peer-to-peer rig. If you are, shame on the IT person who set it up for you.



Sat May 15 06:08:03 2010:   THILLAIRAJAN


Do we have 2 / 3 managed Switch??



Sat May 15 12:34:37 2010:   TonyLawrence


You need to rephrase that question; I'm not sure what you are asking.

Don't miss responses! Subscribe to Comments by RSS or by Email

Click here to add your comments

If you want a picture to show with your comment, go get a Gravatar

Jump to Comments

Many of the products and books I review are things I purchased for my own use. Some were given to me specifically for the purpose of reviewing them. I resell or can earn commissions from the sale of some of these items. Links within these pages may be affiliate links that pay me for referring you to them. That's mostly insignificant amounts of money; whenever it is not I have made my relationship plain. I also may own stock in companies mentioned here. If you have any question, please do feel free to contact me.

Specific links that take you to pages that allow you to purchase the item I reviewed are very likely to pay me a commission. Many of the books I review were given to me by the publishers specifically for the purpose of writing a review. These gifts and referral fees do not affect my opinions; I often give bad reviews anyway.

We use Google third-party advertising companies to serve ads when you visit our website. These companies may use information (not including your name, address, email address, or telephone number) about your visits to this and other websites in order to provide advertisements about goods and services of interest to you. If you would like more information about this practice and to know your choices about not having this information used by these companies, click here.