What is an IP Address?
Every device connected to a network — your laptop, phone, smart TV, or games console — has an IP address (Internet Protocol address). It is a unique number that identifies the device on the network, similar to how a postal address identifies a house.
When data is sent across the internet, each packet is labelled with the sender's IP address and the recipient's IP address, so routers know where to deliver it.
IPv4 Addresses
The most common format is IPv4, which uses four groups of numbers separated by dots. Each number can be from 0 to 255.
Example: 192.168.1.45
Since each number uses 1 byte (8 bits), an IPv4 address is 32 bits total. This gives 2³² = about 4.3 billion unique addresses.
In the early internet era, 4.3 billion seemed like more than enough. But with billions of smartphones, smart devices, and computers all needing addresses, IPv4 addresses are now running out.
IPv4 addresses have been almost completely exhausted. Technologies like NAT (Network Address Translation) have helped delay the problem by letting many devices share one public IP address, but a permanent solution was needed.
IPv6 Addresses
IPv6 is the newer version, designed to solve the shortage. It uses 128 bits, written as eight groups of four hexadecimal digits separated by colons.
Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
IPv6 provides 2¹²⁸ ≈ 340 undecillion unique addresses — enough for every atom on Earth's surface to have its own address, many times over.
| Feature | IPv4 | IPv6 |
|---|---|---|
| Bits | 32 | 128 |
| Notation | Decimal dots (192.168.0.1) | Hex colons (2001:db8::1) |
| Addresses | ~4.3 billion | ~340 undecillion |
| Status | Running out | Gradual adoption |
Public vs Private IP Addresses
- Public IP address: The address your home network uses to communicate with the wider internet. Assigned by your ISP. Every household has a unique public IP.
- Private IP address: The address used inside your home network (e.g. 192.168.x.x). Your router assigns private addresses to each device at home. These are not unique on the internet — millions of homes use the same private ranges.
Your router acts as a translator between your private home network and the public internet using NAT. From the internet's view, all your home devices share one public IP address.
Dynamic vs Static IP Addresses
- Dynamic IP: Changes each time you connect. Most home broadband connections use dynamic IPs — your ISP assigns one from a pool.
- Static IP: Fixed and permanent. Servers and businesses often pay for static IPs so people can always find them at the same address.
Practice Problems
How many bits does an IPv4 address use, and how many unique addresses can it represent? Show how you calculated this.
Show answer
Explain why IPv6 was developed and give one way it differs from IPv4 other than the number of available addresses.