What Is an IP Address and DNS? KS3 Computing Explained

Every device on a network needs a unique address so that data can find its way to the right destination. An IP address provides that address; DNS provides the translation service that converts the human-friendly names we type in browsers into the numerical addresses computers actually use. At KS3 these two concepts underpin everything about the internet.

What is an IP address?

An IP address (Internet Protocol address) is a numerical label assigned to every device connected to a network that uses the Internet Protocol. It serves two purposes: identifying the device (who is it?) and providing its location on the network (where is it?).

Think of an IP address as the postal address of a house. A letter addressed to "17 Turing Road, London, WC2N 5DU" can be routed correctly by the postal system because the address uniquely identifies a destination. An IP address does the same job for data packets crossing a network.

What is the structure of an IPv4 address?

The most familiar version is IPv4 (Internet Protocol version 4). An IPv4 address consists of four numbers, each between 0 and 255, separated by full stops (dots):

192.168.1.1
10.0.0.1
8.8.8.8

Each of the four numbers is stored in 8 bits (one byte), giving 32 bits in total. A 32-bit address can represent 2³² = approximately 4.3 billion unique addresses.

Addresses are divided into two logical parts:

Network part — identifies which network the device belongs to (like a postcode)

Host part — identifies the specific device within that network (like a house number)

Some IPv4 ranges are reserved for private networks (local home or office networks that are not directly accessible from the internet):

Private range | Typical use
192.168.0.0 – 192.168.255.255 | Home routers and local networks
10.0.0.0 – 10.255.255.255 | Larger private networks
172.16.0.0 – 172.31.255.255 | Medium-sized private networks

Devices on your home Wi-Fi typically have addresses like 192.168.1.x. Your router translates between these private addresses and your single public IP address assigned by your internet service provider (ISP) — a process called NAT (Network Address Translation).

What is IPv6 and why was it introduced?

With approximately 4.3 billion possible IPv4 addresses, and more than 15 billion connected devices on Earth, the internet ran out of available IPv4 addresses around 2011. IPv6 (Internet Protocol version 6) was developed to solve this problem.

Feature | IPv4 | IPv6
Address length | 32 bits | 128 bits
Number of addresses | ~4.3 billion | ~340 undecillion (3.4 × 10³⁸)
Notation | Four decimal numbers separated by dots: 192.168.1.1 | Eight groups of four hexadecimal digits separated by colons: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Status | Widespread (legacy) | Growing adoption

IPv6 provides so many addresses that every grain of sand on Earth could have billions of addresses to spare.

What is DNS?

DNS stands for Domain Name System. It is the internet's telephone directory: a distributed, hierarchical database that translates human-readable domain names (like www.bbc.co.uk) into the numerical IP addresses that computers use to route data.

Without DNS, you would need to type an IP address like 151.101.0.81 every time you wanted to visit a website. DNS lets you type bbc.co.uk instead — the translation happens automatically in the background.

How does DNS work step by step?

When you type www.gov.uk into your browser and press Enter, the following process occurs:

Your browser checks its own cache (temporary memory). If it has looked up this address recently, it uses the stored answer and skips the remaining steps.

Your operating system checks its local hosts file — a small text file of manual address overrides.

If still not resolved, your device contacts a recursive DNS resolver — usually provided by your ISP or a public service (e.g. Google's DNS at 8.8.8.8).

The resolver asks a root nameserver — there are 13 root nameserver clusters worldwide — for the authoritative server for .uk domains.

The root server directs the resolver to the TLD (top-level domain) nameserver for .uk.

The TLD server directs the resolver to the authoritative nameserver for gov.uk.

The authoritative nameserver returns the IP address for www.gov.uk.

Your browser uses that IP address to connect to the website's server via HTTP or HTTPS.

The entire lookup takes typically between 1 and 100 milliseconds — fast enough that you never notice it.

Why do IP addresses and DNS matter for the computing curriculum?

Understanding IP addresses and DNS is explicitly required for GCSE computer science and is a foundation topic at KS3. The DfE curriculum asks students to understand how networks, the internet, and associated technologies operate (gov.uk/government/publications/national-curriculum-in-england-computing-programmes-of-study). IP addresses and DNS together explain how any piece of data finds its way from a web server in one country to your browser in another.

They also underpin cyber security topics: DNS spoofing (redirecting DNS lookups to a malicious IP address) and IP address spoofing (faking a source address in a packet) are real attack techniques that GCSE students are expected to know about.

Frequently asked questions

What is an IP address in simple terms for KS3?

An IP address is a unique numerical label assigned to every device on a network. It works like a postal address — it tells the network where to send data and which device sent it. IPv4 addresses look like four numbers separated by dots (e.g. 192.168.0.1); IPv6 addresses are longer and use hexadecimal notation.

What is DNS and why is it needed?

DNS (Domain Name System) translates human-readable domain names (like www.bbc.co.uk) into the IP addresses that computers use to route data. Without DNS, you would need to remember and type the numerical IP address of every website you want to visit. DNS resolvers cache lookups so the translation does not need to repeat on every visit, making browsing faster.

What is the difference between IPv4 and IPv6?

IPv4 uses 32-bit addresses (written as four decimal numbers separated by dots) and supports about 4.3 billion unique addresses. IPv6 uses 128-bit addresses (written in hexadecimal) and supports an astronomically larger number — enough for every device ever likely to exist. IPv6 was developed because the internet was running out of IPv4 addresses as the number of connected devices grew rapidly.

What is the difference between a public IP address and a private IP address?

A public IP address is assigned by your ISP and is visible on the internet — it identifies your router on the global network. A private IP address is assigned by your router to devices on your local network (home or school) and cannot be reached directly from the internet. Addresses in ranges like 192.168.x.x are always private. Your router uses NAT to share a single public IP address among all the devices on your local network.

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