Subnetting: What is it and how does it work?

Subnetting is an indispensable tool for network administrators to manage IP addresses efficiently and to structure networks optimally.

The basics of subnetting

By understanding the basics of subnetting and mastering the steps to implement it, you can help build powerful and scalable network infrastructures.

• IP addresses are a key concept in networks and are used to identify devices on a network.

• Subnetting is the process of dividing a larger IP address space into smaller, logically separated subgroups (subnets).

• This division makes it possible to organise devices in different subnets and to efficiently route data traffic within a network.

• The subnet mask defines how many bits of an IP address are used for the network and how many are used for host identification.
• The abbreviation CIDR stands for Classless Inter-Domain Routing and is used to specify an IP address along with an addition that specifies the number of bits for network identification in a specific pattern. For example, the IP address 192.168.1.0 with a network identifier of 22 bits could be represented in the CIDR notation as 192.168.1.0/22.

The advantages of subnetting

Subnetting has numerous benefits for network performance, security and scalability.

• It helps to use IP addresses sparingly and avoid bottlenecks in the address space.

• Subnets also enable isolation and segmentation of devices, increasing security.

• Subnetting also facilitates the management of devices, services and resources in large networks.

Subnetting steps and techniques

Clear planning and precise execution are required to implement subnetting.

• First determine the number of subnets and hosts needed per subnet. Select an appropriate number of bits for subnet and host identification.

• As an admin, you must determine the subnet mask so that there is enough space for the required hosts. For this you use a mathematical formula: x = 2^n – 2. In this case you still work with the binary system and use powers of two. The variable “n” represents the number of bits in the subnet mask that have the value zero.

• Allocate a range of host IP addresses to each subnet to ensure that enough addresses are available for the devices. Avoid overlap and ensure that the subnet addresses and ranges are correctly aligned.

• Configure the routers and switches in the network to allow traffic between the different subnets. Also add the routing tables to control communication between the subnets.

• Regularly check the network resources and the allocation of IP addresses in the subnets. If necessary, subnetting can be adjusted or extended to meet changing requirements.