Introduces the fundamental concepts, purpose and applications of computer networks.
Explores different network classifications based on geographical coverage, purpose and architecture.
Introduces different physical and logical network structures and how network devices are organised.
Provides practical knowledge of the hardware used to build and connect computer networks.
Introduces the physical and wireless technologies used to transmit data across networks
Explains how network communication is structured using standard models and protocols.
Introduces Ethernet technology and the role of MAC addresses in local network communication
Develops practical understanding of IPv4 addressing and network identification
Teaches learners how to divide networks into smaller subnets and introduces IPv6 addressing.
Introduces network switching and provides practical skills for configuring and managing switches.
Teaches learners how to logically separate networks and carry traffic between network segments.
Introduces routing and explains how routers forward traffic between different networks.
Explores essential network services that support addressing, name resolution and internet connectivity.
Provides practical knowledge of wireless networks and access point configuration.
Introduces fundamental techniques for protecting networks, devices and network traffic.
Develops practical skills for managing, monitoring and troubleshooting computer networks.
Introduces modern networking technologies and the role of networking in cloud and virtualised environments.
Enables learners to apply their networking knowledge by designing, configuring, testing and documenting a complete network solution
Every device that communicates using the Internet Protocol needs an IP address. An IP address helps identify a device and enables network devices such as routers to determine where packets should be delivered.
IPv4, which means Internet Protocol version 4, is one of the most widely studied addressing systems in computer networking. An IPv4 address is made up of 32 binary bits divided into four groups called octets. Each octet contains 8 bits and is normally written as a decimal number between 0 and 255, with the four numbers separated by dots.
Example:
192.168.1.10
This address contains four octets:
192 | 168 | 1 | 10
Understanding the structure of IPv4 addresses is important because it forms the foundation for subnetting, network configuration, routing and troubleshooting.
By the end of this lesson, the learner should be able to:
Define an IPv4 address.
Explain the structure of an IPv4 address.
Explain what an octet is.
Convert simple IPv4 octets between decimal and binary.
Identify the four octets in an IPv4 address.
Explain the network and host portions of an IPv4 address.
Explain the purpose of a subnet mask.
Identify common private IPv4 address ranges.
Distinguish between public and private IPv4 addresses.
Identify common IPv4 address types.
Configure a basic IPv4 address on a computer.
Troubleshoot common IPv4 addressing problems.
IPv4 stands for Internet Protocol version 4.
An IPv4 address is a 32-bit logical address used to identify a network interface on an IP network.
The 32 bits are divided into four groups of 8 bits:
8 bits + 8 bits + 8 bits + 8 bits = 32 bits
Each group is called an octet.
For example:
192.168.1.10
The four octets are:
First octet: 192
Second octet: 168
Third octet: 1
Fourth octet: 10
Cisco describes IPv4 addresses as 32-bit addresses divided into four 8-bit octets and normally represented using dotted-decimal notation.
A bit is the smallest unit of digital information.
A bit can have only two possible values:
0
1
IPv4 uses binary numbers because computers work internally with binary information.
For example, an IPv4 address can be represented in binary as:
11000000.10101000.00000001.00001010
The same address in decimal notation is:
192.168.1.10
The decimal form is easier for humans to read and configure.
An octet is a group of 8 bits.
For example:
11000000
contains eight binary digits.
Because an octet contains 8 bits, it can represent values from:
00000000 = 0
to:
11111111 = 255
Therefore, every IPv4 octet has a decimal value from 0 to 255.
An IPv4 address contains four octets.
Example:
192.168.10.25
| Octet | Value | Position |
|---|---|---|
| First | 192 | Octet 1 |
| Second | 168 | Octet 2 |
| Third | 10 | Octet 3 |
| Fourth | 25 | Octet 4 |
The dots separate the four octets.
General structure:
Octet 1 . Octet 2 . Octet 3 . Octet 4
Consider:
192.168.1.10
Its binary representation is:
192 = 11000000
168 = 10101000
1 = 00000001
10 = 00001010
Therefore:
192.168.1.10
becomes:
11000000.10101000.00000001.00001010
This gives exactly 32 bits.
Each octet has the following binary place values:
128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
For example:
11000000
can be calculated as:
128 + 64 = 192
Therefore:
11000000 = 192
Another example:
00001010
can be calculated as:
8 + 2 = 10
Therefore:
00001010 = 10
An IPv4 address can be divided into two important logical portions:
Network portion
Host portion
The network portion identifies the network.
The host portion identifies a particular device or interface within that network.
The exact boundary between the network and host portions is determined by the subnet mask or prefix length.
For example:
IP address:
192.168.1.25
Subnet mask:
255.255.255.0
The network is:
192.168.1.0
The host portion identifies the particular device, such as:
25
A subnet mask helps a device determine which part of an IPv4 address represents the network and which part represents the host.
A common subnet mask is:
255.255.255.0
It can also be written using CIDR notation as:
/24
The /24 means that the first 24 bits represent the network portion.
Example:
IP address: 192.168.1.25
Subnet mask: 255.255.255.0
CIDR: /24
Network address:
192.168.1.0
Host address:
25
CIDR means Classless Inter-Domain Routing.
CIDR notation represents the number of bits used for the network prefix.
Examples:
192.168.1.10/24
172.16.5.20/16
10.10.10.5/8
Common relationships include:
/8 = 255.0.0.0
/16 = 255.255.0.0
/24 = 255.255.255.0
CIDR notation is widely used in modern IPv4 network configuration.
Historically, IPv4 addresses were divided into classes.
The main traditional classes were:
| Class | First Octet Range | Traditional Use |
|---|---|---|
| A | 1–126 | Very large networks |
| B | 128–191 | Medium-sized networks |
| C | 192–223 | Smaller networks |
| D | 224–239 | Multicast |
| E | 240–255 | Reserved/experimental |
The original IPv4 specification defined class-based address formats with different network and host portions.
Modern networks generally use CIDR rather than relying on traditional classful addressing.
Private addresses are used inside private networks such as:
Homes
Schools
Offices
Computer laboratories
Businesses
Training centres
Common private IPv4 ranges include:
10.0.0.0/8
172.16.0.0/12
192.168.0.0/16
Examples include:
10.0.0.5
172.16.20.10
192.168.1.20
These addresses are intended for private networks and are not directly routable across the public Internet.
A public IPv4 address is an address that can be used for communication across the public Internet, subject to routing and other requirements.
For example, an Internet service provider may assign a public IPv4 address to a customer's router.
A typical small office may therefore have:
Public IP → Router → Private network → Computers
The computers inside the office can use private addresses while the router communicates with the Internet using a public address.
A static IPv4 address is manually configured or otherwise assigned so that it remains consistent.
Example:
IP address: 192.168.1.20
Subnet mask: 255.255.255.0
Default gateway: 192.168.1.1
DNS server: 8.8.8.8
Static addressing can be useful for:
Servers
Printers
Network devices
CCTV systems
Access points
Some infrastructure equipment
A dynamic IPv4 address is normally assigned automatically by DHCP.
DHCP means Dynamic Host Configuration Protocol.
For example, when a computer connects to a network, a DHCP server may automatically provide:
IP address
Subnet mask
Default gateway
DNS server information
This reduces the need to manually configure every computer.
Suppose a computer laboratory has a router with:
192.168.10.1
The network administrator could configure computers as:
Computer 1: 192.168.10.10
Computer 2: 192.168.10.11
Computer 3: 192.168.10.12
Computer 4: 192.168.10.13
With subnet mask:
255.255.255.0
All these computers belong to the same IPv4 network:
192.168.10.0/24
Each device must have an appropriate unique address within the network.
A network address identifies the network itself.
For example:
192.168.1.0/24
Here:
192.168.1.0
is the network address.
It is not normally assigned to an individual host.
A broadcast address is used to communicate with all applicable hosts on an IPv4 network.
For:
192.168.1.0/24
the broadcast address is:
192.168.1.255
Therefore, for a typical /24 network:
Network address: 192.168.1.0
Usable host range: 192.168.1.1–192.168.1.254
Broadcast address: 192.168.1.255
The default gateway is normally the router interface that a device uses when communicating with destinations outside its local network.
Example:
Computer IP: 192.168.1.20
Subnet mask: 255.255.255.0
Default gateway: 192.168.1.1
When the computer needs to communicate with a destination outside its local network, it sends the traffic toward the default gateway.
DNS means Domain Name System.
DNS allows users to use names instead of remembering IP addresses.
For example, a user may enter:
DNS can help resolve the name to an IP address.
This makes Internet services easier for humans to use.
Consider:
192.168.5.25/24
Breakdown:
IPv4 address: 192.168.5.25
First octet: 192
Second octet: 168
Third octet: 5
Fourth octet: 25
Prefix: /24
Subnet mask: 255.255.255.0
Network address: 192.168.5.0
Host portion: 25
Broadcast address: 192.168.5.255
Consider:
10.20.30.45/8
The /8 prefix means the first 8 bits represent the network prefix.
The address can be written as:
10.20.30.45
Binary:
00001010.00010100.00011110.00101101
Each group contains 8 bits.
Routers use IP addressing information to make forwarding decisions.
For example:
Computer A
192.168.1.10
↓
Router
↓
Computer B
192.168.2.20
The router examines the destination IP address and determines where the packet should be forwarded.
This is why understanding network prefixes and subnet masks is important in routing.
A device may fail to communicate because of:
Incorrect IP address
Incorrect subnet mask
Incorrect default gateway
Duplicate IP address
Incorrect DNS configuration
DHCP failure
Network cable problems
Disabled network interface
Incorrect VLAN configuration
Router or switch problems
Write the four octets for each address:
192.168.1.10
10.0.0.25
172.16.5.100
192.168.10.50
Example:
192.168.1.10
Octet 1 = 192
Octet 2 = 168
Octet 3 = 1
Octet 4 = 10
Convert:
192.168.1.10
into binary.
Expected result:
11000000.10101000.00000001.00001010
Learners should also practise converting:
10.0.0.1
172.16.1.10
192.168.10.100
On Windows:
Open Command Prompt.
Type:
ipconfig
Press Enter.
Locate the network adapter currently in use.
Identify:
IPv4 address
Subnet mask
Default gateway
Learners should record the results and explain what each value means.
Open Command Prompt and run:
ping 127.0.0.1
Then test the local gateway, for example:
ping 192.168.1.1
Finally, if Internet access is available, test a known destination.
Discuss the difference between testing the local computer, local network and an external destination.
Create a simple network containing:
1 switch
2 computers
1 router
Example addressing:
Router: 192.168.10.1
Computer 1: 192.168.10.10
Computer 2: 192.168.10.11
Subnet mask: 255.255.255.0
Test whether the computers can communicate.
What does IPv4 mean?
How many bits are in an IPv4 address?
What is an octet?
How many octets are in an IPv4 address?
What is the maximum decimal value of an octet?
Explain dotted-decimal notation.
What is the network portion of an IP address?
What is the host portion?
What is a subnet mask?
What does /24 mean?
What is a private IPv4 address?
Give three private IPv4 address ranges.
What is a default gateway?
What is DHCP?
What is the difference between a static and dynamic IPv4 address?
What is a broadcast address?
Why must devices on the same network have appropriate unique IP addresses?
Convert 192.168.1.10 into binary.
Explain the purpose of a router in an IPv4 network.
Identify three common IPv4 configuration problems.
Design a small computer laboratory network for 10 computers.
Provide:
Network address
IPv4 addresses for the computers
Subnet mask
Default gateway
DNS server
Broadcast address
Explain why your addressing plan allows the computers to communicate.
IPv4
IP address
Bit
Octet
Binary
Dotted-decimal notation
Network portion
Host portion
Subnet mask
CIDR
Network address
Broadcast address
Default gateway
DHCP
DNS
Static IP
Dynamic IP
Private IP
Public IP
Router
An IPv4 address is a 32-bit address divided into four 8-bit octets. Each octet can have a decimal value from 0 to 255, and the address is normally written in dotted-decimal form, such as:
192.168.1.10
An IPv4 address contains a network portion and a host portion. The subnet mask or CIDR prefix determines where the network portion ends and the host portion begins.
Understanding IPv4 address structure is essential before progressing to subnetting, routing, DHCP, VLANs and network troubleshooting.
More learning on IPv4 addressing, subnetting, routing and practical network configuration will be delivered through Senior ICT Academy Campus by either a physical instructor or an online instructor.
Senior ICT Academy Campus: