Network devices

The essentials

Networking devices connect computers, carry signals and direct data to the right place. Each device has a specific job, and case questions often ask which device to use.

Key points

• Modem (MOdulator–DEModulator): converts digital signals from a computer into analog signals for transmission over telephone or cable lines (modulation), and back again at the other end (demodulation).
• Ethernet card (Network Interface Card, NIC): a card that connects a computer to a wired network. Each NIC has a unique MAC address.
• Repeater: regenerates (amplifies) weak signals so they can travel a longer distance. It is used when a cable is longer than its recommended length.
• Hub: connects several computers in a network. Data arriving at one port is sent to all other ports (broadcast). It cannot tell which computer the data is meant for.
• Switch: also connects several computers, but it sends data only to the port of the intended device, using MAC addresses. This reduces unnecessary traffic.
• Router: connects different networks and forwards data packets between them, choosing a path based on IP addresses. A home Wi-Fi router connects the home LAN to the Internet.
• Gateway: a node that connects networks that use different protocols, translating between them. It is the entry and exit point of a network.

Exam tips

• Hub = broadcasts to all; switch = delivers to the right device; router = between networks; gateway = between different protocols.
• When a case says "signal becomes weak over a long cable", the answer is a repeater.

Common mistakes

• Saying a repeater filters or directs data. It only regenerates the signal.
• Confusing a modem (signal conversion) with a router (path selection).