IP Addresses: Everything Has a Number

Lesson 4 · taught by Pip

Here's the plain idea: every device on the internet has its own number, and that number is its address. When a packet needs to travel somewhere, the number is how it knows where to go.

We've already met packets — those little postcards of the net from the last lesson. A postcard is useless without an address on it. The IP address is that address.

Why everything needs a number

Think of a big apartment building. Hundreds of doors, and a letter carrier holding a stack of mail. The carrier doesn't read your letters or know your name by heart. They look at the number on each envelope and walk it to the matching door.

The internet works the same way. Your phone, your laptop, a shop's web server in another country — each one has a number so the network can carry packets to the right door and back. "IP" just stands for Internet Protocol, which is the shared rulebook for how those numbers are written and used. No number, no delivery. 🔦

What the number looks like

The familiar kind of IP address is four small numbers with dots between them, like 142.250.72.14. Each of those four slots holds a value from 0 to 255. String them together and you get an address the network understands.

You don't have to memorize the math. The key thing to feel is that it's just a number, written in a tidy, agreed-upon shape so every machine reads it the same way.

There's a catch, though. Four-slot addresses only allow for a few billion combinations, and the world ran out of room. So a newer, much longer style was invented — it looks like a jumble of letters and numbers separated by colons, and it gives us more addresses than we could ever use. Both styles live side by side today. Same job, bigger pool.

Public and private numbers

Here's a friendly wrinkle. Your home has one public number that the outside internet sees — handed to you by your internet provider. But inside your home, your router gives each gadget its own little private number.

It's like a company with one street address out front, and room numbers inside. Mail arrives at the front desk, and the desk knows which room to walk it to. Your router is that front desk.

This is also why a device's number can change. Move to a new café, join their network, and you borrow a number from their front desk. The address belongs to where you are, not to you personally.

Your turn

On your computer or phone, open the settings for the network you're connected to and look for "IP address." You'll likely see something starting with 192.168 or 10. — that's your private, inside-the-house number. Notice how it's just four small numbers with dots.

One more thing before we sail on

Numbers are great for machines, but you've never typed 142.250.72.14 to visit a website — you typed a name. Something quietly turns the name you remember into the number the network needs. That something is our next stop: DNS, the internet's phone book. 🐙