Lesson Objective
Understand IP Addresses, Subnets and Network Planning
IP addressing is one of the most important foundations of computer networking. Every device that communicates across an IP network needs an address so that data can be delivered to the correct destination.
In this lesson, you will learn how IPv4 and IPv6 addresses work, why subnet masks are used, how CIDR notation represents network size, and how host ranges, network addresses, broadcast addresses and default gateways support network communication.
Audio Lesson
Listen to This Lesson
The audio version explains IP addressing and subnetting in a simple step-by-step way. It covers IPv4, IPv6, subnet masks, CIDR notation, host ranges, network addresses, broadcast addresses, gateways and why subnetting helps organise modern networks.
Concept Overview
IP Addresses Identify Devices and Subnets Organise Networks
An IP address identifies a device on a network. A subnet mask defines which part of the address represents the network and which part represents the host. Subnetting uses this structure to divide a larger address space into smaller networks, making communication easier to manage, secure and troubleshoot.
Learning Algorithm
IP Addressing and Subnetting Workflow
| Step | Process | Technical Meaning |
|---|---|---|
| Step 1 | Identify the device address | The device is assigned an IPv4 or IPv6 address. |
| Step 2 | Separate network and host parts | The subnet mask identifies the network portion and host portion. |
| Step 3 | Apply CIDR notation | The prefix length shows how many bits belong to the network. |
| Step 4 | Find the network address | The network address identifies the subnet itself. |
| Step 5 | Calculate usable host range | The available device addresses are identified inside the subnet. |
| Step 6 | Identify gateway address | The default gateway allows traffic to leave the local subnet. |
| Step 7 | Divide the network into subnets | Subnetting creates smaller sections for departments, services or security zones. |
| Step 8 | Document and test addressing | Addresses are recorded, checked and tested to avoid conflicts. |
Step 1
Identify the device address
Every device on an IP network needs an address. In IPv4, an address usually appears as four decimal numbers, such as 192.168.1.10. In IPv6, the address is much longer and uses hexadecimal notation. The address allows the device to send and receive packets across the network.
Technical Point
An IP address identifies a device so packets can be sent to the correct destination.
Step 2
Separate network and host parts
An IP address contains a network part and a host part. The network part identifies the subnet, while the host part identifies the specific device inside that subnet. The subnet mask shows where this separation happens.
Technical Point
The subnet mask tells the network which part of the IP address identifies the subnet and which part identifies the device.
Step 3
Apply CIDR notation
CIDR notation is a compact way to show the subnet size. For example, 192.168.1.0/24 means the first 24 bits belong to the network portion. A smaller prefix usually creates a larger subnet, while a larger prefix creates a smaller subnet with fewer usable host addresses.
Technical Point
CIDR notation shows subnet size using a prefix such as /24, /26 or /30.
Step 4
Find the network address
The network address identifies the subnet itself. It is not normally assigned to a device. For example, in a typical 192.168.1.0/24 subnet, 192.168.1.0 is the network address. Devices inside that subnet use host addresses from the available range.
Technical Point
The network address identifies the subnet and is reserved for network identification.
Step 5
Calculate usable host range
The usable host range contains the addresses that can normally be assigned to devices. In many IPv4 subnets, the first address identifies the network and the last address is reserved for broadcast. The usable addresses sit between those two boundaries.
Technical Point
The usable host range defines which addresses can normally be assigned to devices.
Step 6
Identify gateway address
The default gateway is usually the router address inside the local subnet. When a device needs to contact another network, it sends the packet to the gateway. The gateway then forwards the packet towards the wider network or the internet.
Technical Point
The default gateway allows devices to communicate outside their local subnet.
Step 7
Divide the network into subnets
Subnetting divides a larger network into smaller networks. A business might create separate subnets for staff devices, servers, guests, security cameras and management systems. This improves organisation, traffic control, security separation and troubleshooting.
Technical Point
Subnetting creates organised network sections for control, security and easier management.
Step 8
Document and test addressing
Good network design requires clear documentation. Address ranges, gateway addresses, reserved addresses, DHCP pools and static devices should be recorded. Testing tools such as ping, traceroute and network scans can help confirm that devices are reachable and correctly placed.
Technical Point
Documenting and testing addresses helps prevent network conflicts and communication failures.
Key Takeaways
What You Should Remember
1. IP Addresses Identify Devices
Every device needs an address to communicate on an IP network.
2. Subnet Masks Split Addresses
The subnet mask separates the network part from the host part.
3. CIDR Shows Prefix Length
CIDR notation explains the size of the network prefix.
4. Network Addresses Are Reserved
The network address identifies the subnet itself.
5. Hosts Use the Usable Range
Devices are assigned usable host addresses inside the subnet.
6. Gateways Connect Outside
The default gateway forwards traffic beyond the local subnet.
7. Subnetting Organises Networks
Smaller subnets support security, management and traffic control.
8. Testing Prevents Errors
Documentation and testing help avoid address conflicts and failures.
Knowledge Check
Quick IP Addressing Quiz
Test your understanding. The questions can change when you refresh them.
Lesson Summary
IP Addressing & Subnetting Summary
IP addressing allows devices to identify each other across networks. Subnet masks and CIDR notation define how addresses are divided into network and host portions. Subnetting organises larger networks into smaller sections, improving management, routing, security and troubleshooting.