Networking Fundamentals

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 LAN (Local Area Network 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.

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 “192.168.0.25” 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. 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.