LAN Switch

How LAN Switches Work

If you have read other HowStuffWorks articles on networking or the internet, then you know that a typical network consists of:

• nodes (computers)
• a connecting medium (wired or wireless)
• specialized network equipment like routers or hubs.

In the case of the Internet, all of these pieces work together to allow your computer to send information to another computer that could be on the other side of the world!

­Switches are another fundamental part of many networks because they speed things up. Switches allow different nodes (a network connection point, typically a computer) of a network to communicate directly with one another in a smooth and efficient manner.

There are many different types of switches and networks. Switches that provide a separate connection for each node in a company's internal network are called LAN switches. Essentially, a LAN switch creates a series of instant networks that contain only the two devices communicating with each other at that particular moment. In this article, we will focus on Ethernet networks that use LAN switches. You will learn what a LAN switch is and how transparent bridging works, as well as about VLANs, trunking and spanning trees.

Networking Basics

Here are some of the fundamental parts of a network:

• Network - A network is a group of computers connected together in a way that allows information to be exchanged between the computers.

• Node - A node is anything that is connected to the network. While a node is typically a computer, it can also be something like a printer or CD-ROM tower.

• Segment - A segment is any portion of a network that is separated, by a switch, bridge or router, from other parts of the network.

• Backbone - The backbone is the main cabling of a network that all of the segments connect to. Typically, the backbone is capable of carrying more information than the individual segments. For example, each segment may have a transfer rate of 10 Mbps (megabits per second), while the backbone may operate at 100 Mbps.

• Topology - Topology is the way that each node is physically connected to the network (more on this in the next section).

• Local Area Network (LAN) - A LAN is a network of computers that are in the same general physical location, usually within a building or a campus. If the computers are far apart (such as across town or in different cities), then a Wide Area Network (WAN) is typically used.

• Media Access Control (MAC) address - This is the physical address of any device -- such as the NIC in a computer -- on the network. The MAC address, which is made up of two equal parts, is 6 bytes long. The first 3 bytes identify the company that made the NIC. The second 3 bytes are the serial number of the NIC itself.

• Unicast - A unicast is a transmission from one node addressed specifically to another node.

• Multicast - In a multicast, a node sends a packet addressed to a special group address. Devices that are interested in this group register to receive packets addressed to the group. An example might be a Cisco router sending out an update to all of the other Cisco routers.

• Broadcast - In a broadcast, a node sends out a packet that is intended for transmission to all other nodes on the network.