← IGCSE Computer Science Paper 1

MAC addresses are given at manufacture

A MAC address is set by the manufacturer when the NIC is made and stored in the NIC, so it normally stays the same on any network the device uses.

Part of: IGCSE Computer Science 0478 — 3.4 Network Hardware — Module 7

Understanding MAC addresses are given at manufacture in IGCSE Computer Science Paper 1

What it does: The two networks show the same MAC address because it does not change when the device moves networks. The manufacturer sets the MAC address during production, so it is already there before the device is sold. A router assigns IP addresses, not MAC addresses. The MAC address is set by the manufacturer. The MAC address is stored in the NIC inside the device, not in the router. The network allocates a new IP address, but the MAC address set at manufacture normally stays the same. Each NIC has its own MAC address, set when that NIC was made. The MAC address is held in the NIC hardware, so it goes wherever the device goes.

Common mistakes: A MAC address is set by the manufacturer when the NIC is made, not at first login. The line should be stage = "manufacture". The program should print mac to show that the MAC stays the same after the device moves networks. Printing network shows the wrong value.

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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
When is a MAC address normally given to a network interface card (NIC)?
When the NIC is made, before it is soldWhen the user joins a network for the first time
Matches
The router gives a device its MAC address when it joins the network
↓
A MAC address is not given by the router or the network. The manufacturer sets it when the NIC is made. (A router assigns IP addresses.)
Applying
Meanings
Term
MAC address set at manufacture
Meaning
A MAC address is set by the manufacturer when the NIC is made and stored in the NIC, so it normally stays the same on any network the device uses.
Practice
nicMac ← "3C-52-82-1A-4F-9B"
Testing
Gaps
nic. ← "3C-52-82-1A-9F-04"
Check Answer
Spots
1stage = "first login"
2mac = "00:1A:2B:3C:4D:5E"

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Quick Questions

1. When is a MAC address normally given to a network interface card (NIC)?
A. When the user joins a network for the first time
B. When the NIC is made, before it is sold ✓
The manufacturer sets the MAC address during production, so it is already there before the device is sold.
2. Who normally sets the MAC address of a NIC?
A. The router on the network
B. The manufacturer of the NIC ✓
A router assigns IP addresses, not MAC addresses. The MAC address is set by the manufacturer.
3. A student takes a laptop from school to home. What normally happens to the laptop's MAC address?
A. It stays the same ✓
B. It changes to match the home network
The MAC address belongs to the NIC and does not change when the device moves to a different network.
4. Where is a MAC address stored?
A. In the network interface card (NIC) ✓
B. In the router that the device connects to
The MAC address is stored in the NIC inside the device, not in the router.
5. Which address normally changes when a phone moves from school Wi-Fi to home Wi-Fi?
A. The IP address ✓
B. The MAC address
The network allocates a new IP address, but the MAC address set at manufacture normally stays the same.

Match the Pairs

MAC address set at manufacture → The manufacturer gives the NIC its MAC address when it is made, before the device is sold
MAC address stored in the NIC → The address belongs to the network interface card inside the device, not to the network it joins
A laptop moves from home Wi-Fi to school Wi-Fi, and its MAC address normally stays the same → home_mac = 3C:5A:B4:1F:92:E7 school_mac = 3C:5A:B4:1F:92:E7
The MAC address is assigned before the device is sold, so it is already fixed when you buy it → factory: NIC made -> MAC 00:1A:2B:3C:4D:5E shop: device sold -> MAC 00:1A:2B:3C:4D:5E
The router gives a device its MAC address when it joins the network → A MAC address is not given by the router or the network. The manufacturer sets it when the NIC is made. (A router assigns IP addresses.)
A MAC address changes each time the device joins a different network → A MAC address normally stays the same on every network because it is stored in the NIC and set at manufacture.

Key Term

MAC address set at manufacture
A MAC address is set by the manufacturer when the NIC is made and stored in the NIC, so it normally stays the same on any network the device uses.

Fill in the Blanks

1. nic ← NewNIC() nic.macAddress ← "3C-52-82-1A-9F-04"
Hint: Type the NIC property that stores the address the manufacturer sets.
2. macBefore ← nic.macAddress moveToNetwork("Cafe WiFi") OUTPUT macBefore = nic.macAddress
Hint: Type the operator that compares whether the two MAC addresses are equal.
3. stage ← "manufacture" IF stage = "manufacture" THEN nic.macAddress ← "00-1A-2B-3C-4D-5E"
Hint: Type the keyword that comes after the condition in an IF statement.
4. CALL makeNIC() CALL setMAC(nic) CALL sellDevice(nic)
Hint: Type the procedure name that gives the NIC its address before the device is sold.
5. network ← "School" network ← "Home" OUTPUT laptop.nic.macAddress
Hint: Type the name of the hardware part that stores the MAC address.

Spot the Error

Question 1
A stage = "first login"
B mac = "00:1A:2B:3C:4D:5E"
C print("MAC set at", stage)
Line A — A MAC address is set by the manufacturer when the NIC is made, not at first login. The line should be stage = "manufacture".
Question 2
A mac = "00:1A:2B:3C:4D:5E"
B network = "School WiFi"
C network = "Home WiFi"
D print("MAC:", network)
Line D — The program should print mac to show that the MAC stays the same after the device moves networks. Printing network shows the wrong value.
Question 3
A def join_network(mac, name)
B print("Joining", name)
C return mac
Line A — A function definition must end with a colon. It should be def join_network(mac, name): so the MAC is returned unchanged.
Question 4
A nic = "WiFi adapter"
B mac = "A4:5E:60:C1:22:9G"
C print(nic, "stores", mac)
Line B — A MAC address is written in hexadecimal, which only uses 0-9 and A-F. G is not a hex digit, so the last pair should be 9B.
Question 5
A mac = "00:1A:2B:3C:4D:5E"
B place = "NIC"
C if place = "NIC":
D print("MAC is kept here")
Line C — A single = assigns a value. An if statement needs == to compare. The MAC address is stored in the NIC, so the test should be if place == "NIC":.

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