Technology Explained

Networking 101: Ethernet, LANs, and How They Work

Aaron Peters 07-07-2017

In the early days of the web, users connected to the internet by dialing from a PC directly into their internet service provider (ISP) of choice. Can you hear the nostalgic screeching of a modem? But for today’s users having all of their devices “on the network” is a given. Businesses have been doing this for many years in the form of using Ethernet-based LANs… but “LAN” and “Ethernet” are not synonymous.


Let’s take a look at how each one contributes to your ability to watch funny cat videos.

What Is a LAN?

A Local Area Network (LAN) is a network whose members are known to one another, but not the rest of the world. LANs pre-date the internet’s predecessor by a decade or so. For example, an older type called token ring allowed you to connect the network in a big loop. Traffic circled the various network members (or nodes) until it reached its destination.

lan token ring

Modern LAN-connected machines can talk to each other as well as external computers (such as the web servers housing awesome sites like MakeUseOf). But those other computers can’t initiate contact in return. How is this possible? It’s because your local network is designated “private” by the IPv4 standard.

What Is a Private IPv4 Network?

Networks that use the internet Protocol version 4 (IPv4) use familiar addresses such as “” for each network node. The IPv4 standard dictates that members of private local networks use a particular range of addresses, as follows:

  • 10.*.*.*
  • 172.16.*.* to 172.31.*.*
  • 192.168.*.*

When you’re trying to contact one of the above addresses, your computer will look towards the other devices it’s connected to directly. In other words, it won’t go outside looking for these nodes (more on what “outside” means in a moment).

Say you want to look at a web page. When you type in its URL, your computer will try to figure out its IP address using a DNS search How to Change Your DNS Settings on Windows (And Why You Might Want To) DNS is an important part of browsing the internet, but the DNS servers your system uses aren't set in stone. Here's how to change that. Read More . If that IP ends up being one of those above (i.e. a local address), your computer will attempt to contact that machine directly. Since they’re members of the same private network, it will find that node.

lan local vs external network

Otherwise, your computer will need to venture into the internet to contact it. One of the nodes on the LAN is designated as the gateway and all the other machines are configured to use this gateway. A gateway will receive these outgoing requests (such as “fetch me the home page of MUO”) and determine where to send it next. Then it’ll send the request, receive the response, and forward that back along to the machine that asked for it. (This process is called network address translation What Is Network Address Translation (NAT) and How Does It Work? Read More .)


The result is your device has one IP address locally, but appears to external machines to have a different one. To see how this works, try the following:

  1. Look for the IP address of your computer on the LAN. Take a look at past MUO articles to do this on Windows using ipconfig How to View & Change Your IP Address in Windows 7, 8, and 10 You can use your computer without even knowing your own IP address, but would you like to know how to check? Here's how to quickly check or change your IP address in Windows. Read More or on Linux and Mac using ifconfig 2 Networking Command Line Tools Everyone Should Know Every computer user, regardless of which operating system you use, should know these command line tools. Read More .
  2. Now, go to the site What Is My IP. The premise of this site is simple: your request is coming from your public address, and the site simply shows this back to you.

whats my ip address mobile site

See how the two are different?

windows 10 ipconfig


When you request the MUO home page, our web server sees a request coming from the external address, not your local one. It also means the web server can’t try to connect to your machine on its own. The gateway (which is typically a router) by default will not forward an incoming request anywhere. In the next section we’ll examine how these two addresses work.

Local (Private) and Public Addresses in Action

Let’s try a little experiment to demonstrate this difference. If you have a Wi-Fi network, connect your phone to it and ping your PC (there are terminal applications available for both iOS and Android) with the following command:

ping [your internal IP address, e.g.]

lan phone ping local

You should get output like that shown above (i.e. that the ping command was successful). Now disconnect from Wi-Fi and try it using the external address you saw earlier (e.g. “8.14.*.*”). You’ll likely get no response, because the command is hitting your router and being ignored (hit Ctrl + C when you get tired of waiting).


lan phone ping external

Accessing Your LAN From Outside

So what use is a network if no one from the outside can ever get into it? They can, but it needs to happen in a controlled manner. Routers can be configured to open specific ports to incoming traffic and direct it to a specific machine within your local network, a process called port forwarding What Is Port Forwarding? Everything You Need to Know What is port forwarding? How can you set it up? Is port forwarding good for gaming? How does it help? Here's what you need to know. Read More .

lan router port forward

Consider your home network’s SSH server How to Set Up SSH on Linux and Test Your Setup: A Beginner's Guide Need to access your Linux computer or server remotely? Here's how to set up and configure SSH on Linux, Windows, and mobile. Read More , which likely has an internal IP such as “” You can configure your router to forward port 22 to this particular local machine. Now when you contact the SSH port of your external address (“8.14.*.*:22”), the router forwards this along to your local machine.

lan port forward

The result is you can reach your machine from the outside via the external address because your router will pass the request along to the LAN. This is also how MakeUseOf’s network can forward port 80 to a web server, allowing you to read this article right now.

Advanced LAN Configurations

In addition to your basic home or business network, there are a couple of other LAN configurations you may not even know you’re using. The following are some of the most common.


Tethering a device to your smartphone How to Connect Mobile Internet to Your PC via Tethering With data tethering, you can use your mobile internet on your PC, laptop, or tablet. All you need is an Android phone! Read More actually creates a (Wi-Fi based) LAN between the two devices. The phone then acts as a gateway, routing the requests it receives to the mobile carrier network (i.e. the “public” network).

“Infrastructure” Devices

lan wireless access point

Most home networking routers assume they will be the only device playing the role of both wired and wireless gateway. But it’s possible to set up a wireless router to serve only as an “access point.” This means it will then take any traffic it receives and forward it on to the “main” router. It’s a fine use for an older router, to act as a “range extender” of sorts.

Peer-to-Peer Networks

Most operating systems will allow you to directly connect two devices together, although this typically comes with some caveats. Firstly, you’ll need to configure them by hand — there won’t be any fancy router doling out IP addresses automatically (unless of course you set up one of the two devices as a DHCP server DHCP Explained: Installing & Configuring A Free DHCP Server [Linux] Read More ).

Second, when you do configure them, you’ll need to do it right. If you set them up with addresses from different ranges (e.g. one with an address of and the other, they won’t be able to see each other. Lastly, by using the network connections of each to connect to the other, you’ll need to take additional steps if any of them are to reach the internet (such as turning your Windows PC into a wireless router Turn Windows Into a Wi-Fi Hotspot and Share Your Internet Connection You've got an Internet connection via a network cable. Can you wirelessly share that connection with other devices? Can you make your Windows computer run like a WiFi router? In short: Yes! Read More ).

What About Ethernet?

A LAN, then, is a network configuration, or topology. So what is Ethernet? Ethernet is one medium (of several) you can use to create a LAN. Others include Wi-Fi, Bluetooth, and USB. These can all be used to create a local network, or can even all co-exist within the same one. While wireless has its conveniences, Ethernet still serves several important roles, as follows:

The main pieces of networking gear in an Ethernet network is the Category-5 cable that runs between two RJ-45 ports. A very basic Ethernet network could consist of just three parts: two nodes with RS-45 ports and the cable running between them. In a home network, this is the equivalent of plugging your device (e.g. an Xbox) directly into the port on your cable modem.

lan p2p network

More complex networks make use of other elements such as hubs and routers. These two terms are easy to mix up, but we’ve explained the difference in greater detail What's the Difference Between Routers, Hubs, and Switches? Are you confused about the differences between a hub, a switch, and a router? Don't worry. The answer is actually quite simple. In this article, we break it down for you. Read More . The important thing to remember is that hubs connect the network internally, and routers connect it with other outside networks. All of the above can also be combined, with a network containing Ethernet connections to devices like desktop PCs or servers and wireless connections to printers, phones/tablets, and devices outside the reach of wired drops.

lan mixed network

Basically, Not All LANs Are Ethernet

Ethernet is one of the oldest, and in many ways still one of the best, media for LANs today. But networks have grown beyond just this one type of connection. And while Ethernet is still a key element in most LANs both at home and at the office, they are not one and the same.

What does your home network look like? Do you have any devices still hard-wired over Ethernet? Prefer Ethernet to other types of connections for certain applications? Let us know in the comments!

Related topics: Computer Networks, Ethernet, LAN.

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  1. Jeffrey W. Mortenson
    February 5, 2018 at 10:45 am

    "Token ring"? Really? You could have *easily* depicted a "star topology" and it would have been a much better primer. "Hubs" and "token ring" do not exist in a modern network.

    • Im an idiot
      February 5, 2018 at 11:09 am

      And yet their example of the "token ring" was not of a modern network. Maybe reread before you bash something you missed

      • Jeffrey W. Mortenson
        February 5, 2018 at 11:14 am

        I did read it, imagine going to buy a new car but you have to go through the scrap yard first. "Yes, those are old cars that no longer operate ... now let's get to the new cars."
        Thanks for your reply, have a great day!