1. Network Interface Card (NIC)
Think of a NIC like a passport. Without one, a device simply isn't allowed to "travel" onto a network — it has no way of sending or receiving anything. Every laptop, desktop, phone, printer or smart TV that connects to a network — whether by a cable or over Wi-Fi — has a NIC built in somewhere inside it, even if you never see it, because it's often built directly onto the motherboard rather than being a separate card you can pull out.
The exam board only really wants one core fact from you here, so let's make sure it's rock solid:
Key Definition
A Network Interface Card (NIC) is required for a computer to connect to a network. It can be wired (using a cable, e.g. Ethernet) or wireless (using Wi-Fi), and it allows a device to send and receive data over that network.
It's worth knowing that the NIC sits alongside other pieces of network hardware, even though the exam focuses on the NIC itself:
- Router — connects networks together (covered fully in Topic 3)
- Wireless Access Point (WAP) — lets wireless devices join a wired network
- Switch — forwards data to the correct device within a LAN, using MAC addresses
- Transmission media — the physical "roads" data travels on (cables or radio waves)
- NIC — the device's own "ticket" to get onto the network in the first place
Analogy
If a network is a road system, the NIC is like the car's licence plate holder and engine combined — without it, the car can't even get onto the road, let alone be identified once it's there. The MAC address (coming up next) is the actual licence plate itself.
Practice Question
Question 1
A smartphone can connect to a network without any visible cable or plug-in card. Explain why the smartphone still needs a NIC.
Question 2
State whether a NIC can be wired, wireless, or both.
2. MAC Addresses & IP Addresses
This is the part of the chapter that trips students up the most, mostly because MAC addresses and IP addresses sound similar and both look like a jumble of numbers and letters. But once you separate them by "where they're used" and "whether they change," it all clicks into place.
MAC Addresses
A MAC (Media Access Control) address is a unique identifier given to every device that communicates over a local area network (LAN). Crucially, it's assigned to the NIC at the point of manufacture — burned into the hardware, essentially — which is why it's described as static: it never changes, no matter which network the device connects to, or how many times it moves between networks.
This matters practically because switches (the hardware that sits inside a LAN directing traffic) use MAC addresses to work out exactly which device on the network a piece of data should go to. Since a MAC address is permanently and uniquely tied to one specific NIC, it's a completely reliable way to identify a device locally.
MAC Address structure (12 hex digits, grouped in pairs):
00 0A 1B | 2C 3D 4F
└────────────┘ └────────────┘
Manufacturer ID NIC serial number
(OUI) — 1st half (unique to that
specific card)
Key Facts — MAC Address
• Represented as 12 hexadecimal digits (48 bits total), usually grouped in pairs, e.g. 00-0A-1B-2C-3D-4F
• First 3 pairs = manufacturer ID (OUI); last 3 pairs = NIC serial number
• Static — never changes, even if the device moves to a new network
• Enough combinations for roughly 281 trillion devices — this comes from 2⁴⁸
IP Addresses
An IP (Internet Protocol) address is also a unique identifier, but it's used to communicate over the internet (WAN) rather than just a local network. Unlike a MAC address, an IP address can be static (fixed, never changes) or dynamic (can change over time).
Here's the important distinction the exam loves to test: a device's MAC address stays the same if it moves to a different network, but its IP address will change, because the IP address depends on which network the device is currently connected to — it's more like a postal address that changes when you move house, rather than a fixed serial number stamped onto you at birth.
- Static IP — used for servers and websites, so they can always be found at the exact same address (imagine if Google's address changed every day — nobody could ever reliably reach it!)
- Dynamic IP — assigned automatically by a DHCP server (Dynamic Host Configuration Protocol), which is far more common for everyday devices like your home laptop or phone
IPv4 vs IPv6
IP addresses come in two versions, and the reason both exist is simply a story about running out of space.
IPv4 — 4 blocks of denary (0-255), 4 bytes total, joined by dots:
12 . 123 . 225 . 32
──── ───── ───── ────
1 byte 1 byte 1 byte 1 byte = 32 bits total
IPv6 — 8 blocks of 4 hex digits, 16 bytes total, joined by colons:
2001:0DB8:3333:4444:5555:6666:7777:8888
──────────────────────────────────────
8 blocks × 16 bits each = 128 bits total
IPv4 vs IPv6 — Head to Head
IPv4: 4 bytes (32 bits), written as 4 denary numbers 0–255 separated by full stops → gives 2³² ≈ 4 billion unique addresses.
IPv6: 16 bytes (128 bits), written as 8 blocks of 4 hex digits separated by colons → gives 2¹²⁸ unique addresses — over a billion for every single person on Earth.
Why does IPv6 even exist?
With over 7 billion people on the planet, and most of us owning several internet-connected devices (phone, laptop, smart watch, smart TV, games console...), 4 billion IPv4 addresses simply isn't enough to go round anymore. IPv6 was designed with a colossal number of addresses specifically to future-proof the internet.
The Classic Mix-Up
Students very often get MAC and IP the wrong way round in exams. Here's the single sentence to lock in your memory:
Memory Trick
MAC = Manufactured (fixed forever, LAN traffic).
IP = Internet (can change, WAN traffic).
Practice Questions
Question 1 (2 marks) — Past-paper style
Computers in a network can be identified using both IP addresses and MAC addresses. Describe two differences between IP addresses and MAC addresses.
Question 2
A laptop moves from a home Wi-Fi network to a coffee shop's Wi-Fi network. State which address (MAC or IP) stays the same, and which one changes. Explain why.
Question 3
Calculate how many bits are in one full IPv6 address, and explain how you got your answer.
3. Router
If the NIC is your device's "passport" and the MAC/IP addresses are its "name and address," the router is the border control officer and postal sorting office rolled into one. It's the piece of hardware that actually makes decisions about where data goes next.
Key Definition
A router is responsible for routing data packets between different networks. It connects a local area network (LAN) to a wider network such as the internet, which is a type of wide area network (WAN).
A really useful everyday example: think about your home Wi-Fi router. Every time you load a webpage, the router has to figure out that the incoming data packets from that website's server need to be sent specifically to your laptop, and not to your smart TV or your sibling's phone, even though they're all connected to the same home network at the same time. That's "sending internet traffic to the correct destination/devices in your home network" in action.
NETWORK B NETWORK C
[PC]--[switch] [switch]--[PC]
\ /
\ /
[ROUTER]------[ROUTER]
/ \
/ \
[switch]--[laptop] [switch]--[printer]
NETWORK A NETWORK D
Routers sit between separate networks, deciding
which direction each packet needs to travel next.
The router does more than just pass data along blindly — the specification highlights four separate jobs it performs:
Routing data packets
Directs data packets between different networks, working out the correct path for each one.
Connecting LAN to WAN
Joins your local area network to the wider internet (a wide area network).
Managing & prioritising traffic
Helps keep connections stable by managing how much data flows through at once.
Assigning IP addresses
Gives devices on the network their IP address (often acting as, or working with, a DHCP server).
Router vs Switch — don't confuse them!
A switch directs traffic within one LAN using MAC addresses. A router directs traffic between different networks (e.g. your LAN and the internet) using IP addresses. A switch never needs to know about the wider internet — a router's whole job is connecting to it.
Practice Questions
Question 1 (3 marks) — Past-paper style
State three tasks carried out by a router.
Question 2
Explain why a home network with several devices (a phone, a laptop, and a smart TV) still only needs one router to connect them all to the internet.