NIC gives access; MAC is a hardware ID
A network interface card (NIC) is the hardware a device needs to join a network. Each NIC gets a MAC (media access control) address at manufacture. Mark scheme wants two elements: it (1) uniquely identifies the device/NIC and (2) is fixed at manufacture. Structure: 48 bits, six pairs of hex digits, e.g. B4-3A-28-1F-09-CD — first 3 bytes are the manufacturer code, last 3 the serial code. Each hex digit is 4 bits (a nibble), so a pair is one byte.
IP address: purpose and three axes
An IP (internet protocol) address is a numerical address allocated by the network so data reaches the correct device; unlike a MAC it is not fixed in hardware and can change. Three axes: format — IPv4 (32-bit, four denary octets 0–255, e.g. 192.168.0.15) vs IPv6 (128-bit, eight groups of four hex digits); persistence — static (same each time) vs dynamic (reallocated each session, via DHCP); scope — public (internet-wide) vs private (LAN-only, not routable).
Router: forward, assign IP, connect LAN
A router forwards data to a specific destination on a network. Three syllabus roles: (1) forwarding — it reads each packet's destination IP address and finds the best path; (2) assigning IP addresses on its local network (often dynamic, via DHCP); (3) connecting a LAN to the internet (WAN) as the gateway. Contrast: a NIC connects one device; a router connects networks and routes between them on IP; a switch forwards within a LAN on MAC addresses.
Drawn from real examiner reports.
MAC address ≠ IP address
A vague "it identifies the device" scores poorly because both do. Mark-scheme split: a MAC address is fixed by the manufacturer at manufacture; an IP address is allocated by the network and can change. A MAC is a 48-bit hex hardware ID of the NIC; an IP gives the device's location for routing. Remember: MAC = which NIC, IP = where the device is.
URL ≠ IP address
A URL such as www.example.com is a human-readable name for a resource; an IP address is the numerical address the network uses to locate a device. The domain name system (DNS) translates the URL into its IP address — they are not the same. In a fill-the-missing-term question this is a classic mix-up: give the numerical network address (IP), not the typed web name (URL).
November 2022 (w22) examiner report: in a fill-the-missing-term question, "the most common incorrect response was the confusion of URL and IP address."
Wrong axis: IPv4/IPv6 for a dynamic IP
Asked to describe a dynamic IP address, weaker candidates describe an IPv4 or IPv6 address (its size/format) — the wrong axis. IPv4 vs IPv6 = format; static vs dynamic = how often it changes; public vs private = where it is valid. Answer "dynamic" on persistence: it is allocated each connection and can change — not "32-bit, four denary octets" (that is IPv4).
June 2023 (s23) examiner report, Q6(b)(ii): "Some candidates provided responses that were more suitable for describing what an IPv4 or IPv6 address is. Candidates are reminded to look at the key terminology in the questions and structure their answer based on this."
Router named when the NIC is meant
When a question describes what one computer needs to join a network, the answer is the network interface card (NIC), not the router — a router directs data between networks, not one device onto one. Rule: one computer joining a network → NIC; directing data / connecting a LAN to the internet → router; forwarding within a LAN by MAC address → switch.
June 2023 (s23) examiner report, Q6(a)(i): on a network-component identification question, "The most common incorrect answer was router" — candidates chose router when a different device was required.
Router works on IP; switch on MAC
Candidates conflate the connecting devices. A NIC connects one device to a network. A router connects networks and forwards between them on logical IP addresses, linking a LAN to the internet. A switch forwards within one LAN on physical MAC addresses. The address type is the giveaway: a router routes on IP, a switch forwards on MAC. Naming the wrong device loses the mark.
One hex digit is 4 bits, not 8
MAC addresses are written in hex, and a question can ask for one octet in binary. The trap is forgetting that each hex digit is exactly 4 bits (a nibble), so a two-digit hex pair is one 8-bit byte — not 4 bits. Convert each digit to its nibble, then join. E.g. hex 4A: 4 = 0100 and A = 1010, so 4A = 01001010 (check: 4×16 + 10 = 74). Give the full 8 bits, not 4.
Fix the IP axis before writing
Every IP question sits on one of three axes; pick it first. Format → IPv4 vs IPv6. Persistence → static vs dynamic. Scope → public vs private. If the term is "dynamic", answer only on persistence; if "IPv6", only on format — this avoids answering the wrong axis.
MAC: anchor on hex structure
State the three MAC facts that score: (1) 48 bits / six pairs of hex digits; (2) manufacturer code (first 3 bytes) + serial code (last 3 bytes); (3) fixed at manufacture, unique per NIC. Each hex digit is 4 bits (a nibble), so any octet converts to binary on demand.
Answer the exact key term
Examiner Key messages stress precise technical terminology, structured around the exact key term. Read the key word — MAC, IP, dynamic, router — and answer only around that term, using precise words (allocated, fixed at manufacture, routes on IP), not everyday language.
This sub-topic is the four pieces of kit and addressing that let devices find each other on a network: the NIC, the MAC address, the IP address, and the router.
Network interface card (NIC) — the hardware a computer needs to connect to (access) a network. Without it a device cannot send or receive data on the network. Each NIC is given a MAC address at manufacture.
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