VLSM Calculator

Variable Length Subnet Mask (VLSM) is a technique used in IP networking to allocate IP addressing resources to subnets according to their individual need, rather than dividing them into fixed-size subnets. This method, a fundamental part of modern network design, prevents the wastage of IP addresses, which is a critical concern, especially with the limited address space of IPv4.

Why is VLSM Important?

Imagine you have a large block of IP addresses to distribute among several departments. One department needs only 10 addresses, while another needs 200. Without VLSM, you would be forced to use a single subnet mask for all, likely creating subnets large enough to accommodate the biggest department. This would leave hundreds of addresses unused in the smaller departments. VLSM solves this by allowing you to use different subnet masks for different subnets, creating a highly efficient and scalable network architecture.

How to Use the Calculator

Our VLSM calculator simplifies this complex process. Just follow these steps:

1. Enter the Major Network IP Address: This is the starting IP address of the block you want to subnet.
2. Define Your Subnets: For each required subnet (e.g., "Engineering", "Sales"), specify the number of hosts it needs to support. You can add as many subnets as you need.
3. Calculate: Click the "Calculate" button. The tool will automatically perform the VLSM calculations, sorting your requirements and allocating the most efficient address blocks.
4. Review the Results: The output table provides a detailed breakdown for each subnet, including the allocated network address, subnet mask, usable IP range, and broadcast address. You can then copy this data or download it as a CSV file for your documentation.