One of the junior admins at my company was studying for his Cisco CCNA. He asked me about Repeaters, Hubs, and Switches. What is the difference? Well, let’s see. A repeater does exactly that- it repeats any electrical signals that come into one port, out its other port. (there are only 2 ports on a repeater). It is a very “dumb” device (no offense to any of you repeaters out there).
Hubs are very similar to repeaters. A Hub is essentially a multiport repeater. Any electrical signal that comes into one port, goes out all other ports. Again, a very dumb device.
A repeater and a hub both work on the Physical Layer of the OSI Model.
On the other hand, you have a switch. A switch is much more intelligent. It keeps track of all Ethernet devices connected to it using their MAC address and recording what port that MAC address is connected to. Then, it intelligently uses that table (MAC Address table) to switch Ethernet frames only to the Ethernet port where that traffic is destined to go to. This saves bandwidth and PC processing power. Additionally, most switches have mangement capabilities that allow you to see what is going on, see what device is on what port, if there are any errors, and configure speed & duplex.
A switch works at the Data-Link layer of the OSI Model, Layer 2.
All of these facts are excellent to remember for your Cisco CCENT/CCNA certification.