Network hardware
Network Interface Card (NIC)
A computer cannot connect to a network without a Network Interface Card (NIC). This is a hardware component (either built into the motherboard or as an expansion card) that provides the physical port for connection and handles the data transmission protocols. Without a NIC, the computer has no way to send or receive data packets over the network medium.
MAC Address
A Media Access Control (MAC) address is a unique identifier assigned to the NIC by the manufacturer. It operates at the Data Link layer and is used to identify devices on the same local network segment.
| Feature | Description |
|---|---|
| Length | 48 bits (6 bytes) |
| Format | 12 hexadecimal digits, typically grouped in pairs separated by colons or hyphens (e.g., AA:BB:CC:DD:EE:FF). |
| Structure Breakdown | First 3 bytes (6 hex digits): Organizationally Unique Identifier (OUI) / Manufacturer ID. This identifies the company that made the NIC. Last 3 bytes (6 hex digits): NIC specific identifier. This is assigned by the manufacturer to ensure uniqueness for that specific card. |
| Purpose | To uniquely identify a device on the local network only. It ensures data frames are delivered to the correct physical device within the same broadcast domain. |
⚠︎ MAC Address Structure and Purpose
Error: Describing a MAC address merely as 'a unique ID for the computer' without mentioning its structure or local scope.
Correction: You must specify that it is 48 bits (6 bytes) long and consists of the OUI (first 3 bytes) and the NIC specific part (last 3 bytes). Also, clarify that it identifies the device on the local network, not globally across the internet.
Correction: You must specify that it is 48 bits (6 bytes) long and consists of the OUI (first 3 bytes) and the NIC specific part (last 3 bytes). Also, clarify that it identifies the device on the local network, not globally across the internet.
IP Address
An Internet Protocol (IP) address is a logical address assigned to a device on a network. Unlike the MAC address, which is physical and permanent, the IP address can change and is used to route data across different networks (including the internet).
Building on the previous concept: While the MAC address gets the packet to the correct building (local network), the IP address ensures it reaches the correct house (specific device) within that building and allows it to travel between buildings.
Types of IP Addresses
There are different types of IP addresses based on their version, assignment method, and scope.
| Type | Characteristics |
|---|---|
| IPv4 Address | 32 bits long. Written in denary (decimal) format, separated by dots (e.g., 192.168.1.1). Each number is between 0 and 255. Contains a network prefix and host number. |
| IPv6 Address | 128 bits long. Written in hexadecimal format, separated by colons (e.g., 2001:0db8::1). Contains 8 groups of 4 hex digits. Consecutive zeros can be compressed using double colons (::). |
| Static IP | A permanent address assigned manually or by a server that does not change. Used for servers (web, email) so they are always reachable at the same address. |
| Dynamic IP | An address assigned automatically by a router/DHCP server that can change each time the device connects to the network. Saves address space for home users. |
| Public IP | A globally unique address assigned by an ISP (Internet Service Provider). It is routable on the internet and identifies the network to the outside world. |
| Private IP | An address used within a local network (e.g., 192.168.x.x, 10.x.x.x). It is not routable on the public internet. Multiple private networks can use the same private IP ranges because they are isolated from each other. |
Describing IPv4 Characteristics
When to use: When asked to describe the characteristics of an IPv4 address.
Why examiners accept this: Examiners look for specific technical constraints. Simply saying 'it uses numbers' is insufficient. You must mention the denary base, the range (0-255), and the 32-bit length.
Example correct phrase: "An IPv4 address is a 32-bit denary number, divided into four octets separated by dots, where each octet ranges from 0 to 255."
Why examiners accept this: Examiners look for specific technical constraints. Simply saying 'it uses numbers' is insufficient. You must mention the denary base, the range (0-255), and the 32-bit length.
Example correct phrase: "An IPv4 address is a 32-bit denary number, divided into four octets separated by dots, where each octet ranges from 0 to 255."
Describing Dynamic IP Addresses
When to use: When asked to describe a dynamic IP address.
Why examiners accept this: You must highlight the changeability and the uniqueness at any given time. Do not confuse it with IPv6 or static IPs.
Example correct phrase: "A dynamic IP address uniquely identifies a device on a network but can change each time the device connects to the network, assigned automatically by a router."
Why examiners accept this: You must highlight the changeability and the uniqueness at any given time. Do not confuse it with IPv6 or static IPs.
Example correct phrase: "A dynamic IP address uniquely identifies a device on a network but can change each time the device connects to the network, assigned automatically by a router."
Router
A router is a network device that connects different networks together (e.g., a home LAN to the Internet WAN). Its primary roles are:
- Routing: Determining the best path for data packets to travel between networks.
- IP Assignment: Often acts as a DHCP server to assign dynamic IP addresses to devices on the local network.
- NAT (Network Address Translation): Allows multiple devices with private IPs to share a single public IP address.
⚠︎ Router vs. Switch/Component Confusion
Error: Identifying a router as just a 'component' or confusing it with a switch that only connects devices within the same network.
Correction: A router specifically controls the path of data packets between different networks. It is the device responsible for assigning IP addresses (via DHCP) and connecting to the ISP. Do not say it 'stores web pages' (that is a cache/server) or 'amplifies signals' (that is a repeater).
Correction: A router specifically controls the path of data packets between different networks. It is the device responsible for assigning IP addresses (via DHCP) and connecting to the ISP. Do not say it 'stores web pages' (that is a cache/server) or 'amplifies signals' (that is a repeater).
Past Paper Style Questions
Q:
Describe the characteristics of an IPv4 address. [4]
A:
- It is 32 bits long.
- It uses denary (decimal) numbers.
- The numbers are between 0 and 255.
- It consists of 4 groups of numbers separated by dots.
Q:
State two differences between IPv4 and IPv6 addresses. [2]
A:
- IPv4 uses denary format, while IPv6 uses hexadecimal format.
- IPv4 is 32 bits long (4 groups), while IPv6 is 128 bits long (8 groups).
(Alternative: IPv4 uses dots as separators, IPv6 uses colons.)
Q:
Describe a dynamic IP address. [3]
A:
- It uniquely identifies the device on the network.
- The address can change (is not permanent).
- It is assigned each time the device connects to the network.
Q:
Identify the network device that assigns IP addresses to devices on a local network. [1]
A:
Router