IP Addressing (Cambridge (CIE) A Level Computer Science) : Revision Note
IP addressing
What is an IP address?
An IP (Internet Protocol) address is a unique identifier given to devices which communicate over the Internet (WAN)
IP addresses are dynamic, they can change
IP addresses make it possible to deliver data to the right device
A device connecting to a network will be given an IP address, if it moves to a different network then the IP address will change
IPv4
Internet Protocol version 4 is represented as 4 blocks of denary numbers between 0 and 255, separated by full stops
Each block is one byte (8 bits), each address is 4 bytes (32 bits)
IPv4 provides over 4 billion unique addresses (232), however, with over 7 billion people and countless devices per person, a solution was needed
IPv6
Internet Protocol version 6 is represented as 8 blocks of 4 hexadecimal digits, separated by colons
Each block is 2 bytes (16 bits), each address is 16 bytes (128 bits)
IPv6 could provide over one billion unique addresses for every person on the planet (2128)
Subnetting
Subnetting is the process of dividing a larger network into smaller, more manageable parts, called subnets (short for sub-networks)
Each subnet works like a mini-network within the main network, allowing devices to communicate more efficiently
Benefits of subnetting include:
Reduces network traffic – less data is broadcast across the whole network
Improves speed and performance – data stays within its local subnet
Increases security – limits access so not all devices can reach all parts of the network
Easier to manage and maintain – changes can be made to one subnet without affecting the rest
Improves organisation – helps group devices by department or function
It's commonly used in larger networks, like schools or businesses, to reduce traffic, keep data local, and make management easier
Public vs private IP addresses
Public IP addresses are assigned to devices that need a constant connection to the internet
Examples:
Web servers
Email servers
Globally unique – no two devices can have the same public IP
Allows devices to be directly accessed from anywhere on the internet
Private IP addresses are assigned to devices on a Local Area Network (LAN) by a router
Not routable on the internet – improves network security
Used for items in a home or office, such as:
Laptops
Phones
Printers
Allows internal communication without exposing devices to the public internet
Static vs dynamic IP addresses
Static IP addresses are fixed IP addresses that do not change
Assigned to devices that need a consistent address
Commonly used for:
Websites
Remote access services
Email or file servers
No management required once set
Allows reliable access from anywhere on the network or internet
Dynamic IP addresses are temporarily assigned when a device connects to the network
Comes from a pool of available IP addresses
Managed automatically by a DHCP server (Dynamic Host Configuration Protocol)
Ideal for devices where a fixed address isn't needed
e.g. laptops, smartphones, or guest devices
Worked Example
Computers on the Internet have IP addresses.
Describe the format of an IP address. [3]
Answer
IPv4
Four groups of denary or hexadecimal digits [1 mark]
Numbers between 0 and 255 / 0 and FF [1 mark]
Each is stored in 1 byte / 8 bits [1 mark]
The whole number is stored in 32 bits / 4 bytes [1 mark]
Separated by full stops [1 mark]
Correct example [1 mark]
OR
IPv6
Eight groups of (Hexadecimal) digits [1 mark]
Numbers between 0 and FFFF [1 mark]
Each is stored in 2 bytes/16 bits [1 mark]
The whole number is stored in 128 bits / 16 bytes [1 mark]
Separated by colons [1 mark]
The first instance of multiple groups of zero can be replaced by a double colon [1 mark]
Correct example [1 mark]
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