Network Hardware

Every networked device has three things that work together.

NIC (Network Interface Card). The hardware that physically connects to the network. Could be a slot card, a USB dongle, or built into the motherboard. Wi-Fi NICs do the same job wirelessly.

MAC address. A unique 48-bit hardware address (12 hex digits, e.g. 00:1A:2B:3C:4D:5E) burned into the NIC at manufacture. Doesn't change. Used to identify the device on the local network — switches forward frames using MAC addresses.

IP address. A LOGICAL address assigned to the device by the network it's on.

• IPv4 = 32 bits (e.g. 192.168.1.5).
• IPv6 = 128 bits (much larger address space).

IP addresses CAN change — when you connect to a new Wi-Fi network, you get a new IP. Used to route packets between networks.

Why both? MAC addresses identify the SPECIFIC HARDWARE on the local network; IP addresses identify the device's CURRENT POSITION in the wider internet. Both are needed.

Cambridge tip. Mark scheme often asks for the difference: MAC is FIXED + HARDWARE, IP is LOGICAL + can change. Don't confuse them.

IP addresses are assigned in one of two ways.

Static IP. Manually configured and PERMANENT. The device always has the same IP.

• Used by servers, network printers, security cameras — anything that needs to be reliably reachable.
• Configuration takes effort; one wrong digit and the device is offline.

Dynamic IP. Assigned automatically by a DHCP server when the device connects to the network. The same device may get a different IP next time it connects.

• Used for client devices (laptops, phones, tablets) — they don't need to be reachable from outside, only outbound connectivity.
• Easy: connect and you get an address.

Cambridge tip. Mark scheme expects 'static is permanent, set manually, used by servers' and 'dynamic is assigned by DHCP, can change, used by clients'.

These four devices look similar from the outside but do different jobs.

Switch. Connects devices WITHIN a network. Reads the destination MAC address of each frame and forwards it ONLY to the port where that MAC lives. Efficient — frames don't waste bandwidth on irrelevant ports.

Hub. Older, simpler. Receives a packet on one port and BROADCASTS it to ALL other ports. Less efficient, less secure (every device sees everyone's traffic). Largely replaced by switches.

Bridge. Connects two segments of the SAME LAN. Forwards traffic between segments based on MAC addresses. Reduces congestion by separating busy areas of a large LAN.

Router. Connects DIFFERENT networks (e.g. home LAN ↔ internet). Reads the destination IP address of each packet and looks up the best path in a routing table. Also typically:

• Acts as the default gateway for the LAN.
• Runs DHCP to hand out dynamic IPs to clients.
• Performs NAT (Network Address Translation) so many devices can share one public IP.
• Includes a basic firewall.

The home 'router'. What you call your home router is usually FOUR devices in one box: router + switch + Wi-Fi access point + modem. Each one is doing the job described above.

Cambridge tip. Examiner reports flag students who say 'a router and a switch do the same thing'. They don't — different addresses (IP vs MAC), different scope (between vs within networks).

WAP (Wireless Access Point). A device that lets wireless devices connect to a wired network using Wi-Fi. Plug a WAP into a switch and any nearby phone/laptop can join the LAN over the air.

In a home, the WAP is built into the router box. In offices/schools, you may have multiple standalone WAPs spread around to give consistent coverage.

Modem (modulator-demodulator). Converts the digital signals coming from a network into the analogue/encoded form the ISP medium uses (cable, DSL, fibre over copper or satellite), and vice versa.

• The modem is what physically connects your home to the internet provider.
• Without a modem you have a LAN; with a modem you have internet.

Cambridge tip. Don't confuse WAP and router and modem. They do three different jobs. Many products combine all three plus a switch — that's a feature of the product, not a sign that the jobs are the same.

A server is a computer that provides a SERVICE to other computers (clients) on the network. Cambridge expects you to recognise the common types:

Server	Role
File server	Central file storage; multiple users access the same files with permissions.
Print server	Manages print jobs and shares printers across the network.
Web server	Hosts websites; responds to HTTP/HTTPS requests with web pages.
Mail server	Handles sending, receiving, storing email (SMTP, IMAP, POP3).
DNS server	Translates domain names (e.g. www.tutopiya.com) into IP addresses.
Application server	Runs and serves business applications.
Database server	Stores and serves database content to applications.

Cambridge tip. Mark scheme expects students to know the SPECIFIC role of each server type — not just 'a server stores stuff'. When a question says 'name a server that…', match the role to the right type.