IP Addressing·Lesson 1 of 10
IP Addressing
The Short Answer
An is a unique number that identifies a device on a network, so data can be sent to it and no other. IP stands for Internet Protocol — the shared set of rules that governs how data is addressed and delivered across networks. Just as a letter needs a street address to reach the right house, every phone, laptop, and server needs an IP address so that messages find their way to exactly the right machine and nowhere else.
The one thing to remember
An IP address answers one question: "which device should this data go to?" Without it, a network would have no way to tell one machine apart from another.
A postal address for your device
Think about how a letter reaches you: it carries your full address, and the postal system uses that address to route it to your door. An IP address works the same way for data. When your laptop asks for a web page, it includes its own IP address as the 'return address' so the reply knows where to come back to — and the web server's IP address as the destination.
Why Do We Need Them?
A is just a group of connected devices. The moment you have more than one device, you need a way to say "send this to that one, not the others." IP addresses are that way. They let data be routed across the room or across the planet, hopping from network to network until it reaches the exact device that the address points to.
Two Parts: Network and Host
Here's an idea that unlocks almost everything else about IP addressing: an IP address is really made of two parts joined together. The identifies which network the device belongs to, and the identifies the specific device within that network. It's exactly like a postal address, where the city and street narrow you down to a neighbourhood, and the house number picks out one home on that street.
How the address gets split into those two parts is decided by something called a , which we cover in its own lesson. For now, just hold on to the mental picture: every IP address = network part + host part.
Two Versions: IPv4 and IPv6
There are two versions of IP addresses in use today. is the original and still the most common — the familiar dotted number like 192.168.1.10. is its newer, much larger successor, written in a longer hexadecimal form like 2001:db8::1. IPv6 exists because the world simply ran out of IPv4 addresses. Here's the headline difference:
| IPv4 | IPv6 | |
|---|---|---|
| Size | 32 bits | 128 bits |
| Looks like | 192.168.1.10 | 2001:db8::1 |
| Total addresses | About 4.3 billion | About 340 undecillion (a huge number) |
| Written with | Decimal numbers and dots | Hexadecimal and colons |
“"An IP address is permanently tied to one specific device, like a serial number."”
Q:What is an IP address, in one sentence?
A: It's a unique number that identifies a device on a network so data can be delivered to it. It has two parts — a network part (which network) and a host part (which device on it) — and comes in two versions, IPv4 (32-bit) and IPv6 (128-bit).
Quick Revision Cheat Sheet
IP address: A unique number identifying a device on a network
IP: Internet Protocol — the rules for addressing and delivery
Two parts: Network part (which network) + host part (which device)
IPv4: 32-bit, dotted decimal, e.g. 192.168.1.10
IPv6: 128-bit, hexadecimal, e.g. 2001:db8::1
vs MAC address: IP is a logical, changeable label; MAC is fixed hardware