In a past Cisco CCENT qualification exam tutorial, we all talked about broadcasts plus the potential of a broadcast surprise. (If you overlooked that one, check out my website’s Lessons section. ) Inside of today’s tutorial, we’ll discuss many different normal network devices plus how they assist to limit broadcast distribution – or in some instances, how they perform not help!
Found in the “do not help” department, we will find hubs in addition to repeaters. These 2 devices operate in Layer 1 regarding the OSI one (the Physical layer), and their sole purpose is to be able to strengthen the power signals sent above the cable. Indicate have anything to do with turning or routing, and they tend not to aid to limit broadcasts. (A hub is actually just a repeater with increased ports. )
One the other side of the coin end of the spectrum, many of us have routers. Routers operate at Layer 3 of typically the OSI model (the Network layer), and by default routers do not ahead broadcasts. They can easily be configured to “translate” certain transmitted types into unicasts, but you’ll find out more about that in your CCNA research.
Since routers carry out not forward shows, there’s a belief that routers have nothing to do with broadcasts. Routers can indeed generate messages, plus they can take them – nevertheless they will not forwards them. That’s a great important distinction.
Between these two two extremes, we discover switches. Switches operate at Part 2 of typically the OSI model (the Data Link layer), and the standard behavior of a switch is in order to accept a transmission and forward it out every additional single port upon that switch apart from the port that first received typically the broadcast.
If that feels like a lot of broadcast forwarding, it is! When we offer an 80-port switch and something port receives a transmit, by default a duplicate of that transmit is going to be forwarded out there the other seventy nine ports. Most likely, certainly not all of these hosts connected to those switchports require to see that broadcast, and mailing unnecessary broadcast outcomes in an unnecessary use of network resources, particularly bandwidth.
Luckily for us all, there exists a way to be able to configure a Cisco switch to limit which ports obtain that broadcast, plus we’ll take a new look at of which method in the particular next installment of my Cisco CCENT certification exam article series!
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