Subnet

Logical subdivision of a larger network.

Each subnet contains a range of IP Addresses that can communicate directly with each other, while traffic between different subnets need to go through a Router.

IP Addresses for Subnets

Subnets can be identified as $a.b.c.d/x$ where $x$ is a subnet mask that determines that the leftmost $x$ bits of the IP Address define the subnet and the remaining define the Hosts. Thus all Hosts on a subnet must share the leftmost $x$ bits of their IP addresses.

Examples

Requirement of IP addresses of hosts on a subnet

On a subnet identified by $223.1.1.0/24$ any devices attached to this subnet are required to have an address of the form $\mathrm{223.1.1.}xxx$, where $xxx$ could be any value.

Subnet Illustration

Here we find the subnets:

• $223.1.1.0/24$
• $223.1.2.0/24$
• $223.1.3.0/24$