A2.1.3 · Network fundamentals
Network devices
By the end you can
Describe what a NIC, switch, router, wireless access point, modem, gateway and firewall each do, and which one a given job needs.
Many different boxes make up a network, and each one has a job. In most homes a single device does all of them, so it is easy to blur them together. The way to keep them straight is to ask of each: what problem does it solve?
The devices#
- Network interface card (): the hardware inside a device (or a Wi-Fi adapter) that connects it to the network. It turns the device's digital data into electrical, light or radio signals and back again, and carries a unique , a 48-bit hardware address written as six pairs of hex digits.
- Switch: connects devices inside one network. It learns which MAC address is on which port and sends each frame only to the port it is meant for, so devices do not see each other's traffic.
- Router: connects different networks. It reads the destination IP address in each packet, looks it up in a routing table and forwards the packet to the next hop, so a packet can cross many routers on its way across the world.
- Wireless access point (WAP): joins wireless devices to the wired network, converting Wi-Fi signals to wired data and back. Several together can cover a building, with devices moving to the strongest one.
- Modem: a modulator-demodulator. It converts digital data to the analogue signal used on a phone line or cable-TV line, and back at the other end.
- Gateway: the gate between two networks that use different protocols. It translates between them, for example between a home network and an ISP's fibre network, or between an old factory protocol and modern Ethernet.
- Firewall: monitors traffic and allows or blocks it by rules (A2.4.1). A hardware firewall sits between the whole network and the outside; a software firewall protects one device and can give per-application control. Firewalls can also set priorities (quality of service), for example putting video calls ahead of games traffic.
One box, many jobs#
The grey box your internet provider gave you is typically a modem, a router, a switch (the Ethernet sockets), a wireless access point, a DHCP server and a firewall, all in one. The journey below follows a request from a laptop out to the internet, passing each job in turn. Step through it.
- Laptopthe NIC sends a frame
- Wireless access pointlink layer
- Switchforwards by MAC address
- Router (with firewall and NAT)forwards by IP address
- Modemdigital to line signal
- Internetbeyond your network
Step 1 of 7 · Laptop
The laptop’s NIC wraps the request in a frame addressed (by MAC address) to the home router, because the website is not on the local network.
Switch: MAC addresses inside the network. Router: IP addresses between networks. That difference is the one the exam asks about.
Where each device works#
A2.1.5 introduces the TCP/IP layers; here is the short version of where devices fit. NICs, switches, modems and wireless access points work at the network interface layer (frames, MAC addresses, signals). Routers work at the internet layer (packets and IP addresses). A firewall mostly inspects the internet and transport layers (addresses and ports), and a modern one may look right up to the application layer. A gateway translates, so it can work at any layer, though the textbooks place it at the application layer.
Forwards a frame to exactly one port, using the destination MAC address.
Chooses the next hop for a packet using its destination IP address.
Lets phones and laptops join the wired network without cables.
Turns a computer’s digital data into a signal for the phone line.
Translates between two networks that speak different protocols.
Blocks traffic to port 22 from outside the school.
Holds the unique MAC address that identifies a device on the local network.
0 of 7 matched
Check yourself
Network devices
Quick questions, made fresh every time and marked here. Do a few until they feel easy.
Exam practice
Paper 1-style questions
5 questions · 15 marks
Write your answer as you would in the exam, then show the mark points and tick each one your answer made. These are our own questions in the style of the exam, not past-paper questions.
1.Describe the function of a wireless access point.
[2]Describe: A detailed account: say what happens, step by step if it is a process.
2.Distinguish between a switch and a router.
[3]Distinguish: Make the differences between two things clear.
3.Identify the device that does each job: (a) lets a laptop connect to a network, (b) converts digital data to and from the analogue signal on a phone or cable line, (c) joins two networks that use different protocols.
[3]Identify: Pick out the answer from the options or the context.
4.Explain the role of a MAC address.
[3]Explain: Give reasons: say what happens AND why, or how one thing causes another.
5.Compare a hardware firewall with a software firewall.
[4]Compare: Similarities and differences, about both things, point by point.
Past papers
Old exam questions on this topic
From HL Paper 1, May 2014 to November 2025. These papers were set on the previous syllabus, so the wording may differ from today's exam, but the topic is the same. Find the questions and markschemes in your school's past-paper pack.
| Paper | Question | Marks | About |
|---|---|---|---|
| November 2025 | 11(a) | 3 | Equipment needed for a wireless LAN |
| November 2022 | 10(a) | 1 | The hardware that makes a LAN wireless |
| May 2021 | 12(a) | 4 | The role of wireless access points |
| November 2020 | 9(a) | 3 | The router joining a school LAN to the internet |
| November 2019 | 10(b) | 4 | What the hardware in a network does |
| November 2017 | 11(a) | 1 | A hardware part of a WLAN besides computers |
In a nutshell
- A NIC connects a device to the network and has a unique MAC address. A switch joins devices on one LAN using MAC addresses; a router joins networks using IP addresses.
- A wireless access point links Wi-Fi devices to the wired LAN. A modem converts between digital data and the analogue signal of a phone or cable line.
- A gateway joins networks that use different protocols and translates between them; a firewall filters traffic by rules, as hardware at the edge or software on a device.
- A home “router” is usually several devices in one box: modem, router, switch, access point, DHCP server and firewall.
- In the TCP/IP model, NICs, switches, modems and access points work at the network interface layer; routers at the internet layer.