Cambridge O Level Computer Science · Syllabus 2210 · Hardware
IP Address
What is IP Address?
An internet protocol address: an address allocated by the network that identifies a device or connection on that network and allows data to be routed to it; it may be allocated statically, staying the same, or dynamically, so that it can change.
This definition is part of the Hardware chapter in Cambridge O Level Computer Science.
IP Address 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 IP Address
- 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.
- 25. “A MAC address changes on every network.” Why wrong It describes the IP address. The MAC address belongs to the card, not to the network. Correct model The MAC address is given at the point of manufacture and does not normally change when the device joins a different network. It is the IP address that is allocated afresh by each network. Exam-safe “A MAC address is assigned at manufacture and stays with the network interface card; the device's IP address is allocated by whichever network it joins.” Check: a laptop is used at school and then at home. Which address changes?The IP address. The MAC address stays the same.
- 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.
Questions students ask about IP Address
What is the difference between a MAC address and an IP address?
A MAC address identifies the network interface card (NIC) and is assigned at manufacture, usually written in hexadecimal; it does not normally change when a device joins a different network. An IP address identifies a device or connection on a particular network and is allocated by that network, either statically or dynamically, so it can change from network to network. A router reads the destination IP address in a packet's header to decide how to forward it.