The Fundamentals of an Ethernet LAN, Explained

Most wired networks use Ethernet technology

Ethernet is the technology that is commonly used in wired local area networks (LANs). A LAN is a network of computers and other electronic devices that covers a small area such as a room, office, or building. It contrasts with a wide area network (WAN), which spans a large geographical area.

Ethernet is a network protocol that controls how data is transmitted over a LAN and is referred to as the IEEE 802.3 protocol. The protocol has evolved and improved over time to transfer data at the speed of more than a gigabit per second.

A family using various internet-connected devices all connected via Ethernet.

Lifewire / Joshua Seong

Many people have used Ethernet technology their whole lives without knowing it. It is likely that any wired network in your office, at the bank, and at home is an Ethernet LAN. Most desktop and laptop computers come with an integrated Ethernet card and are ready to connect to an Ethernet LAN.

What You Need in an Ethernet LAN 

To set up a wired Ethernet LAN, you need the following:

  • Computers and devices to connect: Ethernet connects any computer or other electronic device to its network as long as the device has an Ethernet adapter or network card.
  • Network interface cards in the devices: A network interface card is either integrated into the motherboard of the computer or installed separately in the device. There are also USB versions of Ethernet cards, such as external dongles. An Ethernet card is known as a network card. It has ports where you connect cables. There may be two ports, one for an RJ-45 jack that connects unshielded twisted pair (UTP) cables and one for a coaxial jack on the network card. (Coaxial connections are extremely rare, though.)
  • A router, hub, switch, or gateway to connect devices: A hub is a device that acts as a connecting point between devices on a network. It consists of several RJ-45 ports to which you plug the cables.
  • Cables: UTP (Unshielded Twisted Pair) cables are commonly used in Ethernet LANs. This cable is similar to the kind used for landline telephone sets but fatter, with eight twisted pairs of wires of different colors inside. The end is crimped with an RJ-45 connector, which is a larger version of the RJ-11 jack that plugs into a landline phone.
  • Software to manage the network: Modern operating systems like recent versions of Windows, Linux, and macOS are more than sufficient to manage Ethernet LANs. Third-party software that gives more features and better control is available.

How Ethernet Works 

Ethernet protocol requires technical knowledge in computer science to fully understand how it works. Here is a simple explanation:

When a machine on the network wants to send data to another, it senses the carrier, which is the main wire connecting the devices. If it is free, meaning no one is sending anything, it sends the data packet on the network, and the other devices check the packet to see whether they are the recipient. The recipient consumes the packet. If there is a packet on the highway, the device that wants to send holds back for some thousandths of a second to try again until it can send.

  • What is an Ethernet cable?

    Ethernet cables are the primary connectors used in an Ethernet network. In an Ethernet LAN, Ethernet cables will connect directly from computers to a router/modem so the computers can talk to one another without using the wider internet.

  • How do you run Ethernet cables through walls?

    Make an opening in your wall and thread the cable through. Pull it out through another created space where you want the cable to go. Ethernet cables are designed for a wide variety of use cases and there aren't generally any special precautions to take.

  • Where can you buy Ethernet cables?

    Ethernet cables are sold offline and online, from Amazon to Best Buy and everywhere in-between. If the retailer sells electronics, chances are they'll have Ethernet cables, too.

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