WHAT IS SUBNETTING ?

Subnetting is a method in computer networking used to divide a large IP address network into smaller, more manageable parts called subnets.

For instance,
If a company is given one big block of addresses, subnetting allows them to split that block into smaller groups so that each department, floor, or branch office can have its own segment of the network.

🔑 Key Points About Subnetting:

1. IP Address Basics
   • An IP address has two parts:
     • Network ID → identifies the overall network.
     • Host ID → identifies individual devices (computers, printers, etc.) within that network.
2. Why Subnetting?
   • To use IP addresses efficiently (avoid wasting addresses).
   • To improve network performance (reduce congestion by isolating traffic).
   • To enhance security (different subnets can be controlled separately).
3. Subnet Mask
   • A subnet mask defines how much of the IP address is for the network and how much is for the host.
   • Example:
     • IP: 192.168.1.10
     • Subnet Mask: 255.255.255.0
     • Here, 192.168.1 is the network portion, and .10 is the host portion.
4. CIDR Notation
   • Subnets are often written like: 192.168.1.0/24
   • The /24 means the first 24 bits are for the network, leaving 8 bits for hosts.
5. Example of Subnetting
   Suppose you have a 192.168.1.0/24 network (which gives 256 addresses).
   • If you subnet into /26, you get 4 smaller networks:
     • 192.168.1.0/26 → 64 addresses
     • 192.168.1.64/26 → 64 addresses
     • 192.168.1.128/26 → 64 addresses
     • 192.168.1.192/26 → 64 addresses
   Each subnet can then be assigned to different departments.