# Network Hardware and Addresses

- **Track:** Cambridge IGCSE™ Computer Science (0478 / 0984) (CAMBRIDGE IGCSE 0478)
- **Module:** Section 3: Hardware & Architecture
- **Estimated Duration:** 10 minutes
- **Access:** Open Theory (All-Access for Interactive IDE & Autotests)

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## Theory & Conceptual Background

A **network interface card (NIC)** provides a device with an interface for network communication, wired or wireless. A MAC address identifies an interface on a local network; factory-assigned addresses are a useful basic model, although devices may use private/randomised addresses.

An **IP address** identifies a network connection for routing between networks. IPv4 uses 32-bit addresses, commonly written as four decimal groups. IPv6 uses 128-bit addresses, usually written in hexadecimal groups, supporting a much larger address space. An IP address may change when a device connects elsewhere; do not confuse it with a URL or a person's identity.

A **router** forwards packets between networks, using the destination IP address and routing information. A home router connects the local network to the internet. Many home routers also provide address allocation and wireless access, but those are distinct functions.

## Worked journey

A laptop requests a page from a server on another network. Its NIC transmits on the local network; the router forwards packets towards the server's IP address. DNS supplied the address from the host name. The MAC is useful for local delivery; routers use IP information for the journey between networks.

## Independent application

A laptop changes from home Wi-Fi to school Wi-Fi. Explain why its network configuration can change while the same web URL still works. Identify where NIC, router and DNS each help.

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## Interactive Exercises & Autotest Specifications

### Exercise 1: Application: Network roles (Fill in blank, 30 XP)

**Instructions:**
Work out each answer before submitting. Component providing a device network interface: Device forwarding packets between networks: Address type used for routing: MAC or IP? IPv6 address width in bits:


**Starter Code:**
```text
{"prompt":"Application: Network roles","template":"1. Component providing a device network interface: [blank_1]\n2. Device forwarding packets between networks: [blank_2]\n3. Address type used for routing: MAC or IP? [blank_3]\n4. IPv6 address width in bits: [blank_4]","blanks":[{"id":"blank_1"},{"id":"blank_2"},{"id":"blank_3"},{"id":"blank_4"}],"word_bank":["NIC","router","IP","128","switch","hub","MAC","32","64"]}
```