Network Hardware

This lesson covers the key hardware components used in computer networks: NICs, switches, routers, hubs, wireless access points (WAPs), firewalls, repeaters, bridges, and gateways. Understanding the role of each device is essential for the OCR H446 specification.

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Network Interface Card (NIC)

A Network Interface Card (NIC) is a hardware component that allows a device to connect to a network.

Feature	Detail
Function	Provides a physical interface between the device and the network medium
Types	Wired (Ethernet, RJ45 port) and wireless (WiFi adapter)
MAC address	Each NIC has a unique MAC (Media Access Control) address, a 48-bit hardware address
Location	Built into motherboards or added as a separate card

MAC Address Format

A MAC address is 48 bits, written as 6 pairs of hexadecimal digits:

00:1A:2B:3C:4D:5E

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Hub

A hub is a basic networking device that connects multiple devices in a star topology.

Feature	Detail
Function	Receives data on one port and broadcasts it to ALL other ports
Layer	Physical layer (Layer 1 of OSI model)
Intelligence	None — does not examine or route data
Collisions	High — all devices share the same bandwidth
Status	Largely obsolete — replaced by switches

Why Hubs Are Inefficient

When a hub receives a frame, it sends a copy to every connected port, regardless of the intended recipient. This wastes bandwidth and causes collisions.

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Switch

A switch is a more intelligent device that connects multiple devices in a star topology and forwards data only to the intended recipient.

Feature	Detail
Function	Learns MAC addresses and forwards frames only to the correct port
Layer	Data link layer (Layer 2 of OSI model)
MAC address table	Builds and maintains a table mapping MAC addresses to ports
Collisions	Minimal — each port has its own collision domain
Performance	Much better than a hub — full bandwidth per port

How a Switch Works

1. A device sends a frame to the switch.
2. The switch reads the destination MAC address from the frame header.
3. It looks up its MAC address table to find which port that MAC address is connected to.
4. It forwards the frame only to that port (or floods all ports if the address is unknown).
5. It updates its table by recording the source MAC address and the port it arrived on.

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Router

A router connects different networks and forwards data between them based on IP addresses.

Feature	Detail
Function	Routes packets between different networks (e.g., LAN to WAN, LAN to Internet)
Layer	Network layer (Layer 3 of OSI model)
Addressing	Uses IP addresses to determine the best path for packets
Routing table	Maintains a table of known networks and the best paths to reach them
NAT	Often performs Network Address Translation
DHCP	Often acts as a DHCP server, assigning IP addresses to devices

Router vs Switch

Feature	Switch	Router
Operates at	Layer 2 (MAC addresses)	Layer 3 (IP addresses)
Connects	Devices within the same network	Different networks together
Addressing	MAC addresses	IP addresses
Broadcast	Forwards broadcasts within the LAN	Blocks broadcasts between networks

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Wireless Access Point (WAP)

A WAP provides wireless connectivity, allowing WiFi-enabled devices to connect to a wired network.