What is a Subnet?

A subnet (short for "subnetwork") is a logical division of an IP network. It allows network engineers to break a large network into smaller, more manageable segments.

Why are Subnets Important?

• Improve performance: Smaller networks reduce broadcast traffic and improve efficiency.
• Enhance security: Different subnets can isolate parts of the network, making it harder for threats to spread.
• Better IP management: Subnets help allocate IP address ranges based on departments, floors, or regions.
• Enable routing: Subnets are key for routers to understand how to reach specific devices on a network.

Subnets are defined using CIDR notation (like /24), which tells how many bits of the address are used for the network portion. For example, 192.168.1.0/24 covers 256 IP addresses, from 192.168.1.0 to 192.168.1.255.

CIDR | Subnet Mask | Usable Hosts

--------------------------------------
/32    | 255.255.255.255 | 1
/31    | 255.255.255.254 | 2
/30    | 255.255.255.252 | 2
/29    | 255.255.255.248 | 6
/28    | 255.255.255.240 | 14
/27    | 255.255.255.224 | 30
/26    | 255.255.255.192 | 62
/25    | 255.255.255.128 | 126
/24   | 255.255.255.0  | 254
/23    | 255.255.254.0   | 510
/22    | 255.255.252.0   | 1,022
/21    | 255.255.248.0   | 2,046
/20    | 255.255.240.0   | 4,094
/19    | 255.255.224.0   | 8,190
/18    | 255.255.192.0   | 16,382
/17    | 255.255.128.0   | 32,766
/16    | 255.255.0.0     | 65,534
/15    | 255.254.0.0     | 131,070
/14    | 255.252.0.0     | 262,142
/13    | 255.248.0.0     | 524,286
/12    | 255.240.0.0     | 1,048,574
/11    | 255.224.0.0     | 2,097,150
/10    | 255.192.0.0     | 4,194,302
/9     | 255.128.0.0     | 8,388,606
/8     | 255.0.0.0       | 16,777,214