subnetting is simple

Introduction

This tutorial will guide you through the process of subnetting a network, using the example of a coffee shop requiring multiple subnets. Subnetting is the method of dividing a larger network into smaller, manageable segments. This is crucial for efficient network management and security. By the end of this guide, you will understand how to create subnets, calculate subnet masks, and determine usable host ranges.

Step 1: Understand the Basics of Subnetting

• IP Address: An identifier for a device on a network, typically represented in decimal format divided into four octets (e.g., 192.168.4.0).
• Subnet Mask: A 32-bit number that divides the IP address into the network and host portions (e.g., /24 indicates the first 24 bits are for the network).
• Network ID: The address representing the entire subnet.
• Broadcast ID: The address used to send packets to all devices in a subnet.
• Usable Host Range: The range of IP addresses that can be assigned to devices within a subnet.

Step 2: Define the Requirements

• Given the network ID 192.168.4.0/24, you need to create three subnets for different purposes:
  • Office
  • Front desk and storage room
  • Public use

Step 3: Determine the Number of Required Subnets

• You need to create three separate subnets. Since the original mask is /24, this gives you a total of 256 addresses (192.168.4.0 to 192.168.4.255).
• For three subnets, you may need to borrow bits from the host part of the address.

Step 4: Calculate Subnet Masks and Sizes

• Subnetting to 3 Subnets:
  • Use a subnet mask of /26 (255.255.255.192).
  • This allows for 4 subnets (2^2 = 4) with 62 usable addresses each (64 total - 2 for network and broadcast).

Step 5: List Each Subnet

1. Subnet 1

   • Network ID: 192.168.4.0
   • Subnet Mask: 255.255.255.192 (/26)
   • Host ID Range: 192.168.4.1 - 192.168.4.62
   • Broadcast ID: 192.168.4.63

2. Subnet 2

   • Network ID: 192.168.4.64
   • Subnet Mask: 255.255.255.192 (/26)
   • Host ID Range: 192.168.4.65 - 192.168.4.126
   • Broadcast ID: 192.168.4.127

3. Subnet 3

   • Network ID: 192.168.4.128
   • Subnet Mask: 255.255.255.192 (/26)
   • Host ID Range: 192.168.4.129 - 192.168.4.190
   • Broadcast ID: 192.168.4.191

Step 6: Identify Wasted Subnets

• After creating three subnets with a /26 mask, one subnet (192.168.4.192/26) is not used, resulting in one wasted subnet.

Step 7: Subnetting Practice with More Subnets

• For practice, take the same network ID (192.168.4.0/24) and create 6 subnets.
• Use a subnet mask of /27 (255.255.255.224), which gives you 8 subnets with 30 usable addresses each.

List Each of the 8 Subnets

1. Subnet 1

   • Network ID: 192.168.4.0
   • Host ID Range: 192.168.4.1 - 192.168.4.30
   • Broadcast ID: 192.168.4.31

2. Subnet 2

   • Network ID: 192.168.4.32
   • Host ID Range: 192.168.4.33 - 192.168.4.62
   • Broadcast ID: 192.168.4.63

3. Subnet 3

   • Network ID: 192.168.4.64
   • Host ID Range: 192.168.4.65 - 192.168.4.94
   • Broadcast ID: 192.168.4.95

4. Subnet 4

   • Network ID: 192.168.4.96
   • Host ID Range: 192.168.4.97 - 192.168.4.126
   • Broadcast ID: 192.168.4.127

5. Subnet 5

   • Network ID: 192.168.4.128
   • Host ID Range: 192.168.4.129 - 192.168.4.158
   • Broadcast ID: 192.168.4.159

6. Subnet 6

   • Network ID: 192.168.4.160
   • Host ID Range: 192.168.4.161 - 192.168.4.190
   • Broadcast ID: 192.168.4.191

7. Subnet 7

   • Network ID: 192.168.4.192
   • Host ID Range: 192.168.4.193 - 192.168.4.222
   • Broadcast ID: 192.168.4.223

8. Subnet 8

   • Network ID: 192.168.4.224
   • Host ID Range: 192.168.4.225 - 192.168.4.254
   • Broadcast ID: 192.168.4.255

Conclusion

You have now learned how to subnet a network by creating multiple subnets from a single network ID. Remember to calculate the subnet mask and determine the usable host ranges. Practice with different scenarios to reinforce your understanding of subnetting concepts.