How the VLAN Planner Works
The VLAN & IP Subnet Planner allows network architects to rapidly chop a large Base Network (e.g., `10.0.0.0/16`) into smaller, correctly aligned subnets based purely on the anticipated host-count of each division.
When deploying a new site, administrators rarely want to manually calculate decimal boundaries to ensure that **VLAN 10** (500 hosts) and **VLAN 20** (120 hosts) don't accidentally overlap. This calculator uses strict IPv4 bitwise shifting to automatically jump to the next valid network boundary for the requested CIDR size, piecing the network together sequentially like a puzzle.
Planning Phase Notice
This is a sequential allocation tool designed for rapid initial scaffolding. It allocates blocks in the exact order they are listed. It does not perform advanced fragmentation-gap optimization. Always consult a Senior Network Engineer before writing final configurations to core routing tables.
Example Planning Scenario
Branch Office Deployment
You are assigned a fresh `/22` block (`10.50.4.0/22`) from Corporate for a new branch office. You need to carve out discrete broadcast domains for Servers, Workstations, and Voice traffic.
* Notice how the /23 block skipped the .5 address space to properly align on an even 3rd octet boundary.
Frequently Asked Questions
Why did the calculator skip an IP range?
IPv4 routing dictates that subnet network addresses must land on specific binary boundaries. For example, a `/23` subnet (510 hosts) must always have an even number in the 3rd octet (e.g., `10.0.2.0`, `10.0.4.0`). If the calculator is currently sitting at `10.0.3.0` and you ask for a `/23`, it MUST jump forward over the `.3` space to begin at `10.0.4.0`. This leaves a fragmentation gap behind.
How do I prevent fragmentation gaps?
The best practice in IP Address Management (IPAM) is to always allocate your largest subnets first, working down to your smallest. Try reordering your VLAN list by clicking the trash can and adding the largest host-counts at the top.