IP Addresses - Your Computer's Address
Public vs private, LAN vs internet, and why you need both
What Is an IP Address?
An IP (Internet Protocol) address is a unique number that identifies a device on a network. Think of it as a house address - without it, nobody can send you anything and you can't receive anything.
A typical IP address looks like: 192.168.1.15 (four numbers separated by dots, each between 0 and 255).
Two Types of IP Addresses
Here's the key thing most people don't realise: your device has TWO different IP addresses at the same time.
1. Private IP (LAN IP)
This is the address your DHCPThe service on your router that automatically assigns IP addresses. More Info… server (router) gives your device. It only works inside your home network. Common ranges:
- 192.168.x.x - Used in home routers and small offices. Why not for large networks?192.168.x.x only supports ~65,000 addresses — not enough for universities or large offices with thousands of devices. It also causes conflicts when VPN users connect from home, since both networks may use the same range. That's why large organisations prefer 10.x.x.x instead. Can technically be used in any local network, but not ideal for large organisations.
- 10.x.x.x - Preferred for large networks like universities, hospitals, and corporations. Supports over 16 million addresses and avoids VPN conflicts with home networks.
- 172.16.x.x to 172.31.x.x - Less common, used in some organisations as a middle ground (~1 million addresses).
Your phone might be 192.168.1.15, your laptop 192.168.1.16, your smart TV 192.168.1.17. These addresses only work inside your local network.
2. Public IP (Internet IP)
This is the address your Internet Service Provider (ISP) assigns to your router. It's the address that websites see when you visit them. Check your public IP here.
Every device in your home shares this single public IP. Whether your phone, laptop, or tablet visits a website, the website sees the same address - your router's public IP.
Why Do We Need Both?
There are only about 4.3 billion possible IPv4 addresses. That sounds like a lot, but there are far more than 4.3 billion devices in the world. We simply don't have enough public IP addresses for every device to have its own.
The solution? Private IP addresses. Your home can have dozens of devices, each with a private IP, but they all share one public IP when talking to the internet.
NAT - The Translator
Your router uses a system called NAT (Network Address Translation) to manage this. When your laptop sends a request to a website:
- Your laptop sends it from its private IP (192.168.1.15) to the gatewayYour router - the device that connects your home network to the internet. More Info…
- Your router replaces the private IP with its public IP
- The website sees and responds to the public IP
- Your router receives the response and remembers "this was for the laptop" and forwards it to 192.168.1.15
This is why websites like this one show your router's public IP, not your device's private IP.
IPv4 vs IPv6
IPv4 is the system described above (e.g., 192.168.1.15). It's been around since the 1980s and is running out of addresses.
IPv6 is the newer system with vastly more addresses (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). It has enough addresses to give every grain of sand on Earth its own IP - multiple times over. IPv6 adoption is growing, but IPv4 is still dominant.