MAC Addresses and IP Addresses — Internet and Networking | IGCSE Computer Science

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 7% of your exam marks.

stable

Low

Stable7%

Network topologies, protocols (HTTP, TCP/IP, FTP, DNS) and network hardware appear consistently.

Devices on a network need an address so that data can be sent to the right one. Two addressing schemes are examined: MAC and IP.

MAC address

The (short for Media Access Control) acts as a unique identifier for each network card. The manufacturer burns it into the NIC during production, and it is used to recognise the device on a Local Area Network ().

Key facts:

Static: the MAC address is set at the factory and never changes for the life of the NIC.
48 bits long, usually written as 12 hexadecimal digits grouped into six pairs separated by colons: AA:BB:CC:DD:EE:FF.
The first three pairs identify the manufacturer (Organisationally Unique Identifier, OUI).
The last three pairs are a serial number assigned by the manufacturer.
A device's MAC address stays the same even after the device joins a new network.
The 48-bit address space allows for about 281 trillion different MAC addresses, far more than the number of devices ever made.

IP address

An IP (Internet Protocol) address is a unique identifier assigned to a device when it joins a network, used to identify the device on the internet ().

Key facts:

Can be static (fixed, used for servers and websites that need a permanent location) or dynamic (changes each time the device joins a network, assigned automatically by a DHCP server).
A device's IP address typically changes whenever it joins a different network.
Two versions exist: IPv4 and IPv6.

IPv4

IPv4 is the older version, using 32-bit addresses written as four denary numbers in the range 0 to 255, joined by dots.

Example: 192.168.1.1

Each block (called an octet) is one byte (8 bits).
A full IPv4 address occupies 32 bits in total (4 bytes).
The total number of possible IPv4 addresses is 2³² ≈ 4.3 billion.
That seemed like plenty in 1983, but with 8 billion+ people, smart phones, IoT devices and servers, the 4.3 billion addresses are now exhausted.

IPv6

IPv6 is the newer version, using 128-bit addresses written as eight blocks of four hexadecimal digits, separated by colons.

Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334

Every block holds 16 bits (2 bytes).
The full IPv6 address spans 128 bits (16 bytes) overall.
The total number of possible IPv6 addresses is 2¹²⁸ ≈ 3.4 × 10³⁸, enough to give every person on Earth about 10²⁸ unique addresses.
IPv6 is now being rolled out worldwide alongside IPv4.

Side-by-side comparison

Feature	MAC address	IP address
Stands for	Media Access Control	Internet Protocol
Assigned by	The NIC manufacturer	The network (router / DHCP server)
Static or dynamic?	Static (never changes)	Can be OR

Why both addresses are needed

The two address systems do different jobs:

The gets a packet from a sender, somewhere on the internet, to the destination network. Routers around the world use it.
The MAC address then delivers the packet within the destination network, from the router to the specific device. Switches use it.

Think of it like postal delivery: the IP address is the street address of the building, while the MAC address is the specific person's name on that floor.

Exam tip

MAC address vs IP address — term-and-definition table

What comes up: a table with terms or definitions left blank; you must supply the missing term or its definition for MAC address and IP address.

Write (two marks): (1) An IP address is assigned by the network (via the router or DHCP server) and is used to identify a device on a network — it can change when the device joins a different network. (2) A MAC address is assigned by the manufacturer and is permanently built into the NIC — it uniquely identifies the specific device and does not normally change.

Watch out: the mark scheme credits "assigned by the manufacturer" for MAC and "assigned by the network" for IP — swapping these (e.g. saying IP is permanent or MAC is assigned by the router) loses the mark.

Exam tip

IPv4 vs IPv6 differences

What comes up: state two or more differences between IPv4 and IPv6 addresses.

Write (two marks per pair): each mark requires both sides of the contrast — (1) IPv4 uses 32 bits written as four denary (decimal) groups separated by dots (e.g. 192.168.1.1); IPv6 uses 128 bits written as eight groups of four hexadecimal digits separated by colons. (2) IPv4 digits in each group range from 0 to 255; IPv6 groups range from 0000 to FFFF. A third contrast: IPv4 has far fewer possible addresses than IPv6 (approximately 4.3 billion vs 3.4 × 10³⁸).

Watch out: each difference must state both what IPv4 does AND what IPv6 does — writing only one side (e.g. "IPv6 is 128-bit" without the IPv4 half) earns no mark for that point.