Syllabus & Goals 3 min
Cambridge 3.4 · Network hardware Paper 1 · Computer Systems
By the end of this lesson you can:
- Describe the role of a network interface card (NIC).
- Describe a MAC address and how it is structured.
- Explain the difference between a MAC address and an IP address, and the role of a router.
Recap / Warm-Up 5 min
Unit 2 moved data across a network. This lesson covers the hardware that gives each device its identity and connects it.
Quick starter
You met the MAC address back in Unit 1 (uses of hexadecimal). How many bits is a MAC address, and how is it written?
Reveal the answer
48 bits, written as six pairs of hexadecimal digits, e.g. 00-1C-B3-4F-25-FF.
Key Concept 14 min
1 · Network interface card (NIC)
2 · MAC address
3 · IP address and the router
Worked Example 12 min
(a) MAC vs IP
| MAC address | IP address | |
|---|---|---|
| Set by | Manufacturer (in the NIC) | The network / router (or ISP) |
| Changes? | No (fixed to the device) | Yes (depends on the network) |
| Identifies | The specific physical device | The device's location on a network |
(b) Reading a MAC address
For 00-40-96-AB-12-CD: the first three pairs 00-40-96 identify the manufacturer; the last three AB-12-CD are the device's serial number.
Try It Yourself 12 min
Goal: State what a NIC is used for.
Goal: For the MAC address 3C-22-FB-01-9A-7E, state which part is the manufacturer code and which is the serial number.
Goal: Explain why a laptop keeps the same MAC address but may get a different IP address at home and at school.
📝 Exam Practice 10 min
State the purpose of a network interface card (NIC).
Mark scheme
- It allows a device to connect to a network (1).
Describe the structure of a MAC address.
Mark scheme
- 48 bits, written as six pairs of hexadecimal digits (1).
- First half = manufacturer code; second half = device serial number (1).
Explain one difference between a MAC address and an IP address.
Mark scheme
- A MAC address is fixed/permanent to the device (1)…
- …whereas an IP address can change depending on the network the device is connected to (1).
Recap & Key Terms 3 min
A NIC connects a device to a network and carries its MAC address — a fixed 48-bit hex identifier (manufacturer + serial). An IP address locates the device on a network and can change; a router assigns private IPs and links the network to the internet. That completes Unit 3 — Hardware.
- NIC
- Network Interface Card — hardware that connects a device to a network and holds its MAC address.
- MAC address
- A fixed 48-bit hex identifier unique to a device's NIC.
- IP address
- An address identifying a device's location on a network; can change.
- Router
- Connects a local network to the internet and assigns private IP addresses.
Homework 1 min
Task (≤ 15 min): Write a short paragraph explaining why a device needs both a MAC address and an IP address.
Model answer
The MAC address permanently identifies the physical device (its NIC) and never changes, so the hardware can always be recognised. The IP address identifies where the device is on a network and is assigned by the router/ISP, so it can differ each time the device joins a different network. Together they let data be routed to the right network and the right device.