What is Ethernet?

Online, machines talk to each other via the Internet. When opening a website, your computer asks a server for the site’s files. It then interprets those files and shows you the site. That is an extremely boiled-down version of the process, but it perfectly illustrates how things generally work. However, the Internet is on a global scale. On the other hand, Ethernet facilitates this communication between devices in a local network.

In this article, we will explore Ethernet, how it fits into the grand picture of the Internet, and why those colorful cables we are all familiar with are called Ethernet cables.

This post includes:

• What is Ethernet?
• How are Devices Identified Over Ethernet?

What is Ethernet?

To explain what Ethernet is, we should elaborate a bit more on how a connection on the Internet is established. When your Internet browser (whether on your computer or mobile device) tries to access a website, the connection must first go through a router or a switch. Think of that router or switch as a border checkpoint. On one side is the local area network, and on the other is the Internet. When your browser requests a website, that connection goes through that checkpoint, at which point your ISP picks up the request and routes it through all the necessary servers, routers, and switches until you get your website.

The distinction between Ethernet and the Internet lies in this separation at the router or switch. You can think of Ethernet (or Wi-Fi, which is just wireless Ethernet) as the Internet but for your local area devices. Devices that communicate on the local area side of the router/switch. Here is a quick visual aid.

[Computer] ←Ethernet→ [Router] ←Internet connection→ [World Wide Web]

That is the foundational difference between the two terms. Ethernet is local technology. It connects devices in your local network. It stops at the router, and beyond it, the Internet begins. That is also why the cable you use to plug your computer into your router or switch is called an Ethernet cable. It connects your computer to the local area network, enabling it to connect to the Internet.

However, since Ethernet is a communication standard, a router or switch is not necessary for devices to communicate in a local area. A computer and a printer connected directly via an Ethernet cable will still use Ethernet technology. Most use cases for Ethernet nowadays are through a switch or router, though, because they act as a singular connection point for multiple devices instead of having to connect each individually.

How are Devices Identified Over Ethernet?

We all know that each device that connects to the Internet has a unique IP address that serves as its identifier online. IPs are a fundamental part of the Internet that allows us to connect to the precise websites we need. For example, most everyday users have one IP address, and it is assigned to their router. That is, on the Internet side of things, to use the earlier analogy. On the Ethernet side of things, all devices have individual local IP addresses (192.168.0.1, 192.168.0.2, etc.) that distinguish them.

These local IPs allow your router to remember which device sent the request to the Internet so it can then direct the response correctly. However, there is a small hitch here: Ethernet does not recognize IP addresses. So, when the response comes, the router uses the Address Resolution Protocol to find out the MAC address associated with the local IP that needs the request.

The Address Resolution Protocol (ARP) is a simple but fundamental part of networking. Simply put, it queries all devices in the network about who has the specific local IP address. At that point, the device responds with its MAC address, and the router sends the response from the server to it. ARP is the method used to bridge the gap between the Internet, which works with IPs, and Ethernet, which works with MAC addresses. For more information on MAC addresses and their functionality, check our article on them.

With all of this said, you now know the difference between the Internet and Ethernet, why we need both of them, and the particular roles each plays in our daily online lives.

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