What Is A Subnetwork?

Date First Published: 3rd April 2022

Topic: Computer Networking

Subtopic: Network Setups

Article Type: Computer Terms & Definitions

Difficulty: Medium

Difficulty Level: 6/10

CONTENTS

Benefits
Prefixes

Learn more about what a subnetwork is in this article.

A subnetwork, also known as a subnet is a part of a larger network. It is a separately identifiable part of a network, often a LAN that consists of all the devices in one building or geographical location. Each organisation is responsible for determinining the number and the size of the subnetworks that it creates. In addition, the use of subnetworks enables organisations to stay connected to the internet with a shared network address. This means that all of the devices in a subnetwork have the same prefix to their IP addresses. The process of dividing a network into a subnetwork is known as subnetting. Subnetworks are described in RFC 950.

Benefits

It is beneficial for an organisation to use a subnetwork because it enables network traffic to travel a shorter distance without travelling through unnecessary routers to reach its final destination. It also improves the security of the network as network administrators can reduce network threats by quarantining compromised sections of the network. Using a subnet can reduce network congestion since all connected devices that share traffic are placed on the same subnet. Without a subnet, all devices and servers of the network would see data packets from every other device, which could overload the network.

Prefixes

Subnetworks share the network addresses with each other. The routing prefix is written as the first IP address of the network with a slash. For example, the IP address 123.123.123.0/24 would be the prefix of the IPv4 network. The forwards slash represents the number of bits in the IP address and in this case, 24 bits are allocated for the network prefix and the remaining 8 bits are left for host addressing. Any address ranging from 123.123.123.0 to 123.123.123.255 would belong to that network. Networks may be characterised by subnet mask for IPv4. Similar to an IP address, subnet masks are also expressed in dot-decimal notation. An example of this is that the IP prefix 123.123.123.0/24 would have the subnet mask 255.255.255.0. Subnets are both used in IPv4 and IPv6 networks.

Note:

Network prefixes identify the whole network, subnet masks identify a part of the whole subnetwork, and host numbers identify the host (the device connected to the network).