Cambridge IGCSE Computer Science · Syllabus 0478 · Hardware
Router
What is Router?
Network hardware that sends data to a specific destination on a network: it reads the destination addressing information in each packet, selects an appropriate route and forwards the packet onwards; it can also assign IP addresses and connect a local network to the internet.
This definition is part of the Hardware chapter in Cambridge IGCSE Computer Science.
Router in context
Topic 3 is one machine seen from four distances. Up close, the CPU repeats a single loop — fetch an instruction, decode it, execute it — using named registers and three buses. Step back and the CPU is only useful because input devices and sensors turn physical things into data and output devices and actuators turn data back into physical things. Step back again and nothing survives a power cut unless storage holds it: RAM while the machine runs, secondary or cloud storage afterwards. Step back once more and the machine needs network hardware — a NIC with a MAC address, an IP address and a router — before it can be found and reached by anything else.
Common mistakes with Router
- 24. “MAC and IP addresses are interchangeable.” Why wrong They identify different things, are given by different parties, and are used for different jobs. A network needs both. Correct model A MAC address identifies the network interface card and is given at manufacture. An IP address identifies a device on a network, is allocated by the network, and is what data is routed to. Exam-safe “A MAC address identifies the network interface card and is assigned at manufacture, whereas an IP address is allocated by the network and allows data to be routed to the device.” Check: which of the two does a router read in order to forward a packet?The destination IP address in the packet's header.
- 27. “A router and a NIC are the same device.” Why wrong One is inside the device and gives it a connection; the other is separate hardware that joins networks together. Correct model A NIC is the hardware a computer needs to access a network, and carries the MAC address. A router reads the destination address in each packet, selects a route and forwards it; it can also assign IP addresses and connect a local network to the internet. Exam-safe “A NIC gives one device its connection to a network; a router forwards packets between networks towards their destination.” Check: which of the two provides the MAC address, and which can provide an IP address?Neither provides the MAC address — the manufacturer does, and it is stored on the NIC. The router can allocate an IP address on its own network.