Network Interface Card (NIC)
A Network Interface Card (NIC) is a hardware component that allows a device to connect to a network. Every device on a network must have a NIC (built-in or add-on card).
- Provides a unique MAC address (burned into the card permanently)
- Wired NICs connect via Ethernet cables; wireless NICs connect via Wi-Fi
- Converts data between the device's internal format and the network transmission format
Switch
A switch is a device used to connect multiple devices within a LAN. It operates at the data link layer and uses MAC addresses to direct data frames to the correct device.
- Each device has its own dedicated connection to the switch
- Switch maintains a MAC address table — maps MAC addresses to ports
- Sends data only to the intended recipient (not broadcast to all) — more efficient than a hub
- Reduces unnecessary traffic and collisions
Router
A router connects different networks together — most commonly, it connects a LAN to the internet (WAN). It operates at the network layer and uses IP addresses to route packets.
- Forwards packets between networks by choosing the best route
- Assigns local IP addresses via DHCP
- Often contains built-in firewall and NAT (Network Address Translation)
- Home routers typically also include a switch and wireless access point
Modem
A modem (modulator-demodulator) converts digital data from a computer into an analogue signal suitable for transmission over telephone lines, and vice versa.
- Required to connect to an ISP (Internet Service Provider) via phone/cable line
- Modern broadband connections (fibre optic) may not require a traditional modem
- Often combined with a router in a single home gateway device
Comparison of Devices
| Device | Function | Addresses used | Where used |
|---|
| NIC | Connects device to network | MAC address | Inside every device |
| Switch | Connects devices within a LAN | MAC address | Inside a LAN |
| Router | Connects networks together | IP address | Between LAN and WAN |
| Modem | Converts digital ↔ analogue signal | — | Between home and ISP |
Transmission Media
Wired networks use physical cables to transmit data:
- Copper (ethernet/coaxial) — cheap, flexible, but susceptible to interference and limited distance
- Fibre optic — uses light signals; much faster, longer range, immune to EMI; more expensive
Exam tip: Know the key distinction: a switch uses MAC addresses (within a LAN), while a router uses IP addresses (between networks). The modem converts between digital and analogue. A very common exam question is to describe the role of a router or switch — make sure you mention the type of address used.
⚠️ Common Mistakes
- Saying a switch uses IP addresses — it uses MAC addresses
- Confusing a hub with a switch — a hub broadcasts to ALL devices; a switch sends only to the correct device
- Forgetting that a modem converts digital to analogue (and back)