Subnetting can seem overwhelming at first, but it’s a fundamental skill in networking. In this guide, we’ll go through the key concepts, breakdown the steps, and practice examples so you can master subnetting easily.

**1. What is Subnetting?**

Subnetting is the process of dividing a large network into smaller, more manageable subnetworks (subnets). This helps improve network performance, enhance security, and better utilize IP addresses.

**2. Why Do We Need Subnetting?**

**Efficient IP Addressing**: Reduces wastage of IP addresses by allocating them based on specific needs.**Network Management**: Makes managing large networks simpler.**Performance**: Reduces broadcast traffic and improves overall network performance.**Security**: Allows isolation of subnets for better security control.

**3. Understanding Binary Notation and CIDR**

Before diving into subnetting, we must understand how IP addresses and subnet masks are represented.

**IP Address**: An IP address is a 32-bit number written as four octets (e.g., 192.168.1.1).**Subnet Mask**: Used to divide the IP address into network and host portions. (e.g., 255.255.255.0)**CIDR (Classless Inter-Domain Routing)**: A shorthand for representing the subnet mask. For example, 192.168.1.1/24 means the first 24 bits are the network part.

**4. Subnetting Formula**

The two key formulas for subnetting are:

**Number of subnets**= 2^n, where**n**is the number of borrowed bits.**Number of hosts per subnet**= 2^(number of remaining host bits) – 2.

Let’s see how these work step-by-step.

## Step-by-Step Subnetting Process

**Step 1: Understand the Network Requirement**

Let’s say you’re given the network `192.168.1.0/24`

and you need to create 4 subnets. First, calculate how many bits you need to borrow to create these subnets.

**Step 2: Calculate Subnets**

- To create 4 subnets, you need
**2^n = 4**. - Solving for
**n**, we find**n = 2**. - Borrow 2 bits from the host portion, leaving 6 bits for the host.

**Step 3: Determine the New Subnet Mask**

- Original subnet mask is 255.255.255.0 or
`/24`

. - After borrowing 2 bits, the new subnet mask becomes
`/26`

, meaning the new subnet mask is**255.255.255.192**.

**Step 4: Calculate Subnet Ranges**

With `/26`

, each subnet will have **64 IP addresses**. The ranges are as follows:

- Subnet 1:
**192.168.1.0 – 192.168.1.63** - Subnet 2:
**192.168.1.64 – 192.168.1.127** - Subnet 3:
**192.168.1.128 – 192.168.1.191** - Subnet 4:
**192.168.1.192 – 192.168.1.255**

## Example: Subnetting 192.168.1.0/24 into 8 Subnets

**Step 1: Identify the number of subnets**

- 8 subnets means
**2^n = 8**. Therefore,**n = 3**(we need to borrow 3 bits).

**Step 2: Calculate the New Subnet Mask**

- Original:
`/24`

(255.255.255.0). - New Subnet Mask:
`/27`

(255.255.255.224).

**Step 3: Calculate Subnet Ranges**

Each subnet will have **32 IP addresses**

- Subnet 1:
**192.168.1.0 – 192.168.1.31** - Subnet 2:
**192.168.1.32 – 192.168.1.63** - Subnet 3:
**192.168.1.64 – 192.168.1.95** - Subnet 4:
**192.168.1.96 – 192.168.1.127** - (and so on)

## Common Subnetting Questions

**How do I calculate the subnet mask from a given number of subnets?**

- To calculate the subnet mask, use the formula
**2^n = number of subnets**. Once you know how many bits to borrow, you can adjust the original subnet mask.

**How do I know how many hosts are in each subnet?**

- The number of available hosts in a subnet is given by the formula
**2^(number of host bits) – 2**. Subtracting 2 accounts for the network and broadcast addresses.

## Conclusion

Subnetting can seem like a complex concept, but by breaking it down into smaller, manageable steps, you’ll master it in no time. The key is to practice with different examples and apply the formulas consistently.

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