Kids IT Lab No.4 | Network

What Is an IP Address?

Every device on the Internet has an "IP address" — something like a street address. Without one, packets have nowhere to go and no website can load. In this article we'll cover the format of IP addresses, the difference between global and private IPs, and how to check your own phone's IP — all explained with diagrams.

So what exactly is an IP address?

An IP address is a number assigned to every computer, smartphone, game console, or server connected to a network. Just as every house has an address, every networked device has a number, and data is sent to that number.

The common IPv4 format looks like 192.168.1.10 — four numbers from 0 to 255, separated by dots. There are only about 4.3 billion possible combinations, so a newer standard called IPv6 (which uses much longer numbers) is being used alongside it.

An IP address is similar to an address, but it's not the name itself. Humans remember names like digitalkodomo.jp, while computers convert those names into IP addresses behind the scenes. The system that does this conversion is called DNS. In short, domain names are human-friendly labels; IP addresses are machine-friendly destinations.

Global IPs and private IPs

IPv4 vs IPv6 (the difference in address length) IPv4 has ~4.3 billion addresses and is running out. Migration to IPv6 is underway. IPv4 (current standard — running low) 192.168.1.10 4 numbers 0–255 = 32 bits = ~4.3 billion addresses → Fewer than the world's population (8 billion). Already not enough. IPv6 (new standard — gradually spreading) 2001:db8:85a3::8a2e:370:7334 8 groups of hex = 128 bits = ~340 undecillion addresses → More than the grains of sand on Earth. Won't run out for centuries. Why is IPv4 running out? → IoT devices (appliances, cars, sensors) exploded in number — machines need more IPs than people. ISPs in Japan are migrating to dual IPv6/IPv4. Your router handles the switch automatically.
Fig 1: IPv4's 4.3 billion addresses are not enough, so IPv6 (effectively unlimited) is taking over. The switch usually happens transparently.

Devices inside your home (phones, PCs, game consoles) each receive a private IP like 192.168.x.x from your router. These numbers only work inside your home and never go out to the Internet.

When communicating with the outside world, your router uses a single "global IP" assigned by your ISP (NTT, au, etc.). The whole household shares this one number. From a website's perspective, every family member looks like the same single IP.

What is an IP address used for?

IP address layout in a home network Each device gets a "home-only number"; the whole home gets one "world-facing number" Inside (private IPs) Numbers that work only inside the home Phone 192.168.1.10 PC 192.168.1.11 Game console 192.168.1.12 TV 192.168.1.13 Printer 192.168.1.14 Smart bulb 192.168.1.15 Wi-Fi router (NAT) Bridges inside ↔ outside → Outside (Internet) Assigned by ISP — one per home Global IP 126.45.78.123 Everyone in the house appears as this same IP to the outside → Websites see all visitors from one home as one unit Changes when you switch ISP
Fig 2: Each home device gets a private IP; the whole home gets one global IP. The router translates between them.

Website administrators can log visitors' global IPs and use them for analytics, blocking abuse, or showing region-specific content (e.g., showing a Japanese page to Japanese IPs).

Gaming and calling apps also involve IP addresses. Terms like "NAT type" or "port forwarding" in games come from the router translating between private and global IPs. It usually works automatically, but running your own game server or home server requires understanding this system.

How to check your IP address

To find your global IP, just search "what is my IP" in a browser — the site will display it. For your private IP: on Windows, open Command Prompt and type ipconfig; on Mac, go to System Settings → Wi-Fi → Details; on a phone, go to Settings → Wi-Fi → your connected network. Private IPs usually start with 192.168.x.x or 10.x.x.x.

Comparing those numbers reveals the structure of your network. Your phone and PC on the same home Wi-Fi will differ only in the last number of their private IPs. Switch to mobile data and your global IP changes. Use a VPN and your apparent IP becomes the VPN provider's address. Watching those changes is a great way to understand how network traffic flows.

Watch out for these common mix-ups

Things to keep in mind with IP addresses
  • Never show your global IP on social media or in a stream. It can be a target for attacks.
  • "Your IP can identify you personally" is half true, half false. Only your ISP has the link between your IP and your name — a third party can't reach it without official legal process.
  • On a café or school Wi-Fi, everyone appears to be coming from the same IP. If one person causes trouble, it can affect everyone else on that connection.

How will this help you in the future?

Server management, cloud operations, security investigations, app development — IP addresses come up every day in almost every IT role. "Identify by IP," "block by IP," and "determine location by IP" are standard concepts in web advertising, logistics apps, and streaming services.

Reading logs also relies on IP addresses: "this IP has failed to log in many times," "a sudden spike from an overseas IP," "which device on the company network is sending traffic." If you're heading into networking or security, IP addresses are unavoidable bedrock knowledge.

Try it today

3 steps to get started
  1. Search "what is my IP" in a browser and note your home's global IP address.
  2. Check your private IP in your phone or PC's settings (it should start with 192.168).
  3. Switch between home Wi-Fi and mobile data and see whether your global IP changes.

Summary

An IP address is the network address of a device. There are two kinds: private IPs inside your home and a global IP facing the outside world. Your router translates between them. Just checking your own IP gives you a much clearer picture of how the Internet is structured — and it's the foundation for everything in networking and security.

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