IPv4 Allocation Planner

Introduction:

IPv4 address space is finite, so careful subdivision keeps networks efficient and secure. This interactive planner lets you define a parent Classless Inter-Domain Routing (CIDR) block, split it into child subnets, preview host capacity, broadcast boundaries, and wastage, and confirm that each allocation meets design goals before routers or firewalls are touched.

Under the hood, the page runs entirely in your browser. It validates every network address, calculates binary masks, and updates statistics with a dynamic interface. A dynamic chart illustrates remaining space, while inline tables highlight first and last usable addresses. Export utilities generate ready-to-share CSV and JSON snapshots without any server calls or external storage.

Use the planner before migration projects, lab builds, classroom demonstrations, or managed service handovers to document subnetting decisions and share results with colleagues instantly, avoiding costly re-addressing later. Verify allocations against organisational policies; the planner provides calculation accuracy but assumes you implement appropriate security controls and address assignments in production.

Technical Details:

The application relies on a browser-based calculation engine that converts dotted-decimal inputs to 32-bit integers, applies bitwise masks, and rerenders results instantly through a dynamic interface. No network requests occur after loading, ensuring offline readiness and sub-millisecond updates on typical laptops.

All state remains in volatile memory inside your browser tab. When you copy or download outputs, the page creates temporary blobs on the fly and discards them immediately after action completion, guaranteeing that sensitive addressing schemes never touch external servers, cookies, or persistent logs.

Feature Breakdown

Realtime validation

Input fields watch for invalid octets or prefix sizes and highlight errors instantly, preventing malformed addresses from propagating into your plan.

Auto CIDR sizing

Enter a host target and the calculator selects the smallest subnet that fits, reserving extra blocks for growth without manual bit mathematics.

Interactive utilisation chart

A responsive donut graph refreshes as you edit, clearly illustrating used, free, and reserved address space for immediate capacity awareness.

One-click exports

Buttons generate CSV, JSON, or a screenshot so you can document designs or attach them to change requests in seconds.

Quick filter & search

Live text filtering narrows large allocation tables in real time, helping you locate specific departments or VLANs even in sprawling enterprise ranges.

Calculations & Scoring:

The planner converts prefixes to host counts and back again using fundamental IPv4 arithmetic. Below is the core formula and a worked example.

Formula

hosts = 2(32 – prefix) − 2

Example

For a /24 network:

All calculations occur locally; your addressing data never leaves the device.

Step-by-Step Guide:

Follow these steps to build and export an allocation plan.

1. Type the base block into the Network address field, e.g., 10.0.0.0.
2. Select an appropriate Prefix from the dropdown to set the parent CIDR.
3. Check the Utilisation panel for immediate percentage feedback.
4. In the plan table, fill Hosts and optional Notes, then click Add to insert a subnet.
5. Use the Filter plan… box to isolate rows as the table grows.
6. Open the CSV, JSON, or Chart tab and use Copy or Download buttons to share or archive the plan.

FAQ:

Quick answers to common questions.

Troubleshooting:

Resolve common issues quickly.

• NaN values appear – Ensure the base address is valid dotted-decimal and prefix between /1 and /30.
• Download buttons inactive – Pop-up blockers can intercept file blob creation; allow downloads for this tab.
• Chart shows nothing – Add at least one allocation so the chart receives data.
• Cannot type in Hosts – Field only accepts positive integers; remove commas or spaces.
• Percentage seems wrong – Remember the summary excludes the base network and broadcast addresses when calculating usable hosts.

Advanced Tips:

Work faster and avoid surprises.

• Use non-overlapping notes like “DMZ” or “Campus-WiFi” for quick filtering later.
• Allocate the largest subnets first to minimise fragmentation.
• Keep one /24 free as an emergency pool in critical environments.
• Export JSON and commit it to version control for audit trails.
• Pin the tab; browser refresh is the only reset mechanism.

Glossary:

Key terms used throughout the planner.

CIDR

Notation combining an address with its prefix length.

Subnet

Logical subdivision of an IP network.

Broadcast address

Last address; reaches all hosts in the subnet.

Wildcard mask

Inverse of a subnet mask, used in ACLs.

VLAN

Layer-2 segment identified by a numerical tag.