CAIE 9618 · Paper 1 · Topic 1.2.8

Network Hardware

Routers · Switches · Hubs · WAPs · NICs · Bridges · Repeaters

CSZone Cambridge International AS & A Level Computer Science 9618

NIC & Hub

The Basics

NIC — NETWORK INTERFACE CARD

Allows a device to connect to a network. Every NIC has a unique MAC address (48-bit, burned in at manufacture). Can be wired (Ethernet) or wireless (Wi-Fi). Operates at Layer 2 (Data Link) of TCP/IP model.

HUB

Broadcasts all incoming data to every port. No intelligence — doesn't know which device needs the data. Creates unnecessary traffic; collision domain. Obsolete — replaced by switches.

Switch

Intelligent Frame Forwarding

A switch learns which MAC address is connected to each port. It builds a MAC address table and forwards frames only to the correct port — unlike a hub which broadcasts to all.

Operates at Layer 2 (Data Link) — forwards based on MAC address

Creates individual collision domains per port — reduces congestion

Enables full-duplex communication on each port simultaneously

Layer 3 switches can also route by IP address (managed switches)

Used in LAN environments — the standard device in modern wired networks

Router

Connecting Different Networks

A router connects different networks together (e.g. your LAN to the internet). It forwards packets based on IP addresses, consulting its routing table to decide the best path.

Operates at Layer 3 (Network/Internet layer)

Forwards packets based on destination IP address

Maintains a routing table — maps networks to interfaces

Can perform NAT — maps private IPs to one public IP

Provides DHCP — assigns IP addresses to devices

Home routers often include built-in switch + WAP

WAP, Bridge & Repeater

Other Key Network Devices

WAP — WIRELESS ACCESS POINT

Creates a Wi-Fi network by connecting wirelessly to devices and wired to a switch/router. Broadcasts SSID. Does not route — purely a wireless extension of a wired LAN.

BRIDGE

Connects two network segments and filters traffic between them based on MAC address. Reduces traffic on each segment.

REPEATER

Amplifies/regenerates a weakening signal to extend the range of a network. Operates at Layer 1 (Physical). Does not interpret data — just boosts the signal.

Device Comparison Table

Which Layer? Which Address?

Device	Layer	Address Used	Intelligence
Hub	Layer 1	None	None — broadcasts all
Repeater	Layer 1	None	None — just amplifies
Bridge	Layer 2	MAC	Filters by MAC
NIC	Layer 2	MAC	Identifies device
Switch	Layer 2	MAC	Forwards to correct port
WAP	Layer 2	MAC	Wireless ↔ wired bridge
Router	Layer 3	IP	Routes between networks

Exam Practice

Cambridge-style questions

Question 1

State two differences between a hub and a switch, and explain why switches are preferred in modern networks.

4 marks

1 mark

Hub broadcasts data to all ports; switch sends data only to the port of the destination MAC address

1 mark

Hub has one collision domain (all ports); switch creates a separate collision domain per port

1 mark

Switch reduces unnecessary traffic — only the intended device receives the data

1 mark

Switch is more efficient and secure as data is not broadcast to all devices on the network

Common Mistakes

Don't lose easy marks

1

Saying a router uses MAC addresses — routers forward packets using IP addresses (Layer 3). Switches use MAC addresses (Layer 2). Confusing these two is a very common exam error.

2

Thinking a WAP routes traffic — a WAP connects wireless devices to a wired network, but it does NOT route packets between different networks. Routing is done by the router.

3

Saying a repeater reads or filters data — a repeater simply amplifies the physical electrical/wireless signal. It has no intelligence and no knowledge of MAC or IP addresses.

Topic Summary — 1.2.8

Key Points

HUB

Broadcasts to all — Layer 1 — obsolete

SWITCH

MAC table, port-specific — Layer 2 — modern LAN standard

ROUTER

IP routing, connects networks — Layer 3 — also NAT/DHCP

NIC

Connects device to network — unique MAC address burned in

WAP

Wireless access to wired LAN — extends network wirelessly

REPEATER / BRIDGE

Repeater: extend range (Layer 1) · Bridge: join segments (Layer 2)

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