Subnet and Subnet

 Posted on October 4, 2024  |  

What is a Subnet?

A subnet is a way to divide a large network into smaller, more manageable pieces. Think of it like dividing a big city into neighborhoods. Each subnet (neighborhood) has its own group of devices (houses), but all are still part of the same overall network (city).

What is a Subnet Mask?

A subnet mask is a number used to help identify which part of an IP address belongs to the network (city) and which part identifies the device (house). It’s like a divider that separates the network part from the device part in an IP address.

Simple Example: IP Address and Subnet Mask

Let’s say you have the following IP address and subnet mask:

  • IP Address: 192.168.1.10
  • Subnet Mask: 255.255.255.0

This IP address and subnet mask help identify:

  • What network this device is in (like which city it belongs to).
  • What device it is within that network (like which house in the city).

Visual Breakdown of IP Address and Subnet Mask

Let’s break down the IP address and subnet mask using a visual approach:

Step 1: Convert IP Address to Binary

An IP address is made up of four numbers (each between 0 and 255). In binary, the IP address 192.168.1.10 becomes:

192      . 168      . 1        . 10
11000000 . 10101000 . 00000001 . 00001010

Step 2: Convert Subnet Mask to Binary

The subnet mask 255.255.255.0 also has four numbers. In binary, it looks like this:

255      . 255      . 255      . 0
11111111 . 11111111 . 11111111 . 00000000

Step 3: Identify Network and Host Parts

A subnet mask is used to divide the IP address into two parts:

  • Network part: The part of the IP address that identifies the network (like identifying which city).
  • Host part: The part that identifies the specific device within that network (like identifying the specific house).

In the subnet mask 255.255.255.0, the 1s represent the network part, and the 0s represent the host part. So, for the IP address 192.168.1.10:

  • Network Part: 192.168.1 (because the first three sections are covered by the 1s in the subnet mask).
  • Host Part: 10 (the last section is covered by the 0s in the subnet mask).

Diagram: How Subnet Mask Divides IP Address

Here’s a simple visual showing how the subnet mask divides the IP address:

IP Address:    192.168.1.10
Subnet Mask:   255.255.255.0

Binary IP:     11000000.10101000.00000001.00001010
Binary Mask:   11111111.11111111.11111111.00000000

Network Part:  11000000.10101000.00000001 (192.168.1)
Host Part:                         00001010 (10)
  • The first 24 bits (the 1s in the subnet mask) represent the network.
  • The last 8 bits (the 0s) represent the host.

Visualizing a Network with Subnets

Let’s say you have a large network (192.168.1.0/24), which consists of all the IP addresses from 192.168.1.0 to 192.168.1.255. You can divide this large network into smaller subnets.

The notation /24 is part of something called CIDR notation, which stands for Classless Inter-Domain Routing. CIDR notation is a shorthand way to represent the subnet mask.

The number after the / (in this case, 24) tells us how many bits are used for the network portion of the IP address.

For example, if you use a subnet mask like 255.255.255.192, it will break the network into smaller subnets, each with fewer devices.

Example: Dividing the Network

Main Network: 192.168.1.0/24

Subnet 1: 192.168.1.0/26
Subnet 2: 192.168.1.64/26
Subnet 3: 192.168.1.128/26
Subnet 4: 192.168.1.192/26

Each subnet has its own range of IP addresses and can have its own devices. This way, you can better manage the network traffic and security.

Key Points

  • Subnet: Think of it as a smaller group within a large network.
  • Subnet Mask: A tool that divides the IP address into a network part and a host part.
  • Network Part: The part of the IP address that identifies which network the device belongs to.
  • Host Part: The part of the IP address that identifies the specific device in the network.
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