What do switches do?

Answer 1

A switch is a device that segments networks into different subnets. Segmenting the network into different subnets keeps one network from overloading with traffic. Therefore, a switch forwards all data in the data layer and sometimes the network layer as it filters the data. A switch allows a connection to be established and it terminates a connection when there is no longer a session to support.

Prior to switches there were hubs. Hubs also connected multiple independent (connected) modules in a network, but they were not as efficient as switches. Since most switches work in Layer 2, and not in Layer 1 like a hub, they are better at filtering data. A switch looks for Ethernet MAC addresses, keeps a table (the bridge forwarding table) of these addresses, and navigates the switch between ports. The switch prevents collisions and gives full bandwidth to each connection at the switch port. Switches save bandwidth by only sending traffic to destinations that have traffic. When a switch switches Ethernet frames, they monitor the traffic for the response from that frame and see what device, on what port, responds to that flooded frame. There are different types of switches that range from "dumb" switches that lack manageability and can monitor only 4-8 ports to "managed" switches that can get statistics on switch traffic, monitor connections, and hard-code up to 96 port speeds and duplex. Then again, there are "chassis-based" switches with blades or cards that perform not just switching, but routing and intrusion detection too! If you are interested in this, look into Cisco's Catalyst 6500 Series. Another type of switch preferred by large enterprises is the "Layer 3 Switch," because it has the functionality of a router .