← IGCSE Computer Science Paper 1

What a MAC address is

A unique hardware address given to one network interface card (NIC). Each NIC has its own, so a device with Wi-Fi and Ethernet has two. It identifies the hardware, not the network.

Part of: IGCSE Computer Science 0478 — 3.4 Network Hardware — Module 6, ACARA Digital Technologies Years 9–10 — Networked Systems and Access Control — Module 14, WA Computer Science ATAR Year 11 — Network Communications — Module 35, WA Computer Science ATAR Year 11 — Cyber Security — Module 18

Understanding What a MAC address is in IGCSE Computer Science Paper 1

What it does: The two NICs are separate pieces of hardware, so their MAC addresses are different. The MAC address points to the NIC hardware. It does not describe which network the device is on. Each NIC has its own unique MAC address, so a laptop with Wi-Fi and Ethernet has two. MAC stands for Media Access Control. A MAC address is unique to one NIC. No two NICs should have the same MAC address. One NIC means one MAC address. The count depends on the number of NICs. A MAC address is written as hexadecimal pairs and identifies one NIC.

Common mistakes: A MAC address is written in hexadecimal, so each digit must be 0-9 or A-F. G is not a hexadecimal digit. The last pair should be 5E. Each network interface card has exactly one MAC address, so macs_per_nic should be 1, not 2.

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This module's key terms are also in a printable crossword (Modules 325–341) and word search (Modules 325–354).

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Learning
Duo
A MAC address identifies which part of a device?
The network it is connected toIts network interface card (NIC)
Matches
laptop (Wi-Fi + Ethernet) = 1 MAC address
↓
A MAC address belongs to a NIC, not to the whole device. A laptop with Wi-Fi and Ethernet has two NICs, so it has two MAC addresses.
Applying
Meanings
Term
MAC address
Meaning
A unique hardware address given to one network interface card (NIC). Each NIC has its own, so a device with Wi-Fi and Ethernet has two. It identifies the hardware, not the network.
Practice
DEVICE <- "Laptop"
Testing
Gaps
nic1. ← "00:1A:2B:3C:4D:5E"
Check Answer
Spots
1nic1 = "Wi-Fi adapter"
2mac1 = "00:1A:2B:3C:4D:5G"

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Quick Questions

1. A MAC address identifies which part of a device?
A. Its network interface card (NIC) ✓
B. The network it is connected to
A MAC address belongs to the hardware (the NIC), not to the network. It is a hardware address.
2. A laptop has both a Wi-Fi adapter and an Ethernet port. How many MAC addresses does it have?
A. One, shared by the whole laptop
B. Two, one for each NIC ✓
Each NIC has its own unique MAC address, so a laptop with Wi-Fi and Ethernet has two.
3. Which statement about a MAC address is correct?
A. It is a network address
B. It is a hardware address ✓
A MAC address is tied to the hardware. A network address, such as an IP address, depends on the network.
4. What does MAC stand for in MAC address?
A. Media Access Control ✓
B. Machine Address Code
MAC stands for Media Access Control.
5. How many NICs can share the same MAC address?
A. None, each NIC has a unique one ✓
B. All NICs in the same building
A MAC address is unique to one NIC. No two NICs should have the same MAC address.

Match the Pairs

00:1A:2B:3C:4D:5E → An example MAC address: a unique hardware identifier for one network interface card (NIC)
Wi-Fi NIC + Ethernet NIC → Two NICs in one device, so the device has two MAC addresses
Each NIC has its own MAC address, so a laptop with Wi-Fi and Ethernet has two different ones → wifi_mac != ethernet_mac
A MAC address is a hardware address that belongs to the NIC, not a network address → MAC address -> NIC
laptop (Wi-Fi + Ethernet) = 1 MAC address → A MAC address belongs to a NIC, not to the whole device. A laptop with Wi-Fi and Ethernet has two NICs, so it has two MAC addresses.
MAC address = network address that changes on each network → A MAC address is a hardware address for one NIC. It does not depend on the network. An IP address is the network address.

Key Term

MAC address
A unique hardware address given to one network interface card (NIC). Each NIC has its own, so a device with Wi-Fi and Ethernet has two. It identifies the hardware, not the network.

Fill in the Blanks

1. nic1.mac ← "00:1A:2B:3C:4D:5E"
Hint: Type the short property name for a NIC's hardware address.
2. IF wifi.mac <> ethernet.mac THEN OUTPUT "Different hardware" ENDIF
Hint: Type the operator that means not equal. Two NICs never share an address.
3. nics ← ["Wi-Fi", "Ethernet"] macCount ← LENGTH(nics)
Hint: Type the function that counts the items in a list. Each NIC has one MAC address.
4. address ← "MAC" OUTPUT "Hardware, not network"
Hint: Type the keyword that displays a message on screen.
5. wifiNIC.mac ← "00:1A:2B:3C:4D:5E" ethNIC.mac ← "00:1A:2B:3C:4D:5F" laptop.macCount ← 2
Hint: Type how many MAC addresses a laptop with Wi-Fi and Ethernet has.

Spot the Error

Question 1
A nic1 = "Wi-Fi adapter"
B mac1 = "00:1A:2B:3C:4D:5G"
C print("NIC:", nic1, mac1)
Line B — A MAC address is written in hexadecimal, so each digit must be 0-9 or A-F. G is not a hexadecimal digit. The last pair should be 5E.
Question 2
A nic = "Ethernet card"
B macs_per_nic = 2
C print(nic, macs_per_nic)
Line B — Each network interface card has exactly one MAC address, so macs_per_nic should be 1, not 2.
Question 3
A nic_list = ["Wi-Fi", "Ethernet"]
B mac_count = len(nic_list) - 1
C print(mac_count)
Line B — Every NIC has its own MAC address. A device with Wi-Fi and Ethernet has two NICs, so it has two MAC addresses. Subtracting 1 gives the wrong count; it should be len(nic_list).
Question 4
A pc = "Laptop"
B nic = "Wi-Fi adapter"
C mac = "3C:22:FB:10:9A:01"
D print(mac, "identifies", pc)
Line D — A MAC address identifies one network interface card, not the whole device. The device can have several NICs. The line should print nic.
Question 5
A mac = "00:1A:2B:3C:4D:5E"
B ip = "192.168.1.20"
C mac_type = "network address"
D print(mac_type)
Line C — A MAC address is a hardware address belonging to the NIC. It is not a network address. The line should be mac_type = "hardware address".

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