Beginner · 7 min read · Updated 2026-11
What is an IP address?
Every device on a network has a number so others can find it. Here's how those numbers work, in plain language.
When your laptop talks to a website, both need an address — just like sending a letter. On a network that address is the IP address. The common kind, IPv4, is four numbers from 0 to 255 separated by dots, like 192.168.1.10.
Private and public
Addresses that start with 192.168, 10., or 172.16–31 are private: they only work inside your home or office. Your router has one public address that the whole world sees, and it shares it among all your devices. That's why every phone in a house can show the same “public IP”.
See your own
On Linux, ip a shows your device's addresses. The one next to inet is your private IPv4 on the local network.
$ ip -4 addr show | grep inet inet 127.0.0.1/8 scope host lo inet 192.168.1.42/24 scope global eth0
The /24 at the end
192.168.1.42/24 means the first 24 bits (192.168.1) identify the network and the last part (42) identifies the device. Everything from 192.168.1.1 to 192.168.1.254 is on the same network and can talk directly. This idea — the subnet — is the foundation of all networking, and our subnet calculator tool does the math for you.