Network Subnetting: The Box Method
More than 10 years ago, I studied system administration and network security. Today, I’m revisiting my knowledge, which hasn't been in use for a while.
One of the topics I’m revisiting is network subnetting. In today’s world, it’s hard to imagine anyone manually calculating networks on paper, but I still believe it's a fundamental skill worth practicing from time to time.
In this post, I’ll briefly explain the "box method" I was taught a decade ago to help visualize and understand subnetting.
Why Subnetting Matters
Before diving into the method, let’s quickly recap why subnetting is important. Subnetting allows network administrators to break a large network into smaller, manageable sub-networks, each with a specific range of IP addresses. This helps in:
- Optimizing IP address usage
- Improving network security
- Increasing network efficiency and reducing congestion
By subnetting a network, we can create multiple networks, manage traffic better, and improve performance.
The Box (Square) Method
The box method (also called the square method) is a visual approach to subnetting that helps break down and understand IP address spaces. It uses simple visual grids to represent how a large network can be subdivided into smaller subnets.
Step-by-Step Guide
1. Draw a Box
Suppose we have a network 192.168.1.0, which gives us 256 IP addresses in the range:
192.168.1.0 - 192.168.1.255
Place 0 and 255 in the opposite corners of the box.
2. Divide the Box in Half Horizontally
Divide the box in half. Add new numbers in the corners: 127 and 128. This gives us two subnets with 128 IP addresses each:
192.168.1.0–192.168.1.127192.168.1.128–192.168.1.255
3. Divide the Box in Half Vertically
Next, divide the box vertically. For each box, divide the range by 2 and add the first and last IP addresses to the corners.
Now, we have 4 subnets, each with 64 IP addresses:
192.168.1.0–192.168.1.63192.168.1.64–192.168.1.127192.168.1.128–192.168.1.191192.168.1.192–192.168.1.255
4. Continue Dividing
You can continue dividing the box as much as needed, ensuring that each box contains at least 2 addresses.
Why Use the Box Method?
By dividing the network visually, you can easily determine the subnet range, broadcast address, and usable IPs for each subnet.
TL;DR: Watch the Video
If you'd rather watch this in action, check out the video version of this post on YouTube:
Watch it on YouTube
Final Thoughts
Although manual subnetting may seem outdated in a world of automated network tools, it’s still an important skill. It helps build a deep understanding of how networks work and improves your ability to troubleshoot and configure networks effectively.
Take a few minutes to practice subnetting using the box method. It might help you in ways beyond just getting IP addresses right.
That's it for now!