IPv4 Allocation Planner

Introduction:

IPv4 subnetting divides the 32-bit address space into logically isolated segments so that traffic stays local, routing tables stay compact, and scarce addresses are conserved. Each subnet is defined by a network address and a prefix length that forms a binary mask, determining the portion reserved for network identification versus individual host numbering.

Allocation planning applies Variable Length Subnet Masking (VLSM) to carve differently sized subnets from a larger parent block. By matching host requirements to the smallest possible subnet, you minimise waste. The planner feeds your network address and prefix into a reactive engine, recalculating utilisation, derived CIDR blocks, and host ranges as you add or delete sub-allocations.

An IT administrator reserving segments for servers, printers, cameras, and guest Wi-Fi can prototype an address plan in minutes, then export tidy CSV or JSON for audit systems and config templates. Remember: mistakes in addressing propagate quickly; always validate plans in a lab or staging environment before updating production routers.

Technical Details:

Variable Length Subnet Masking lets you translate host demands into the most economical subnet sizes. For each request, the algorithm rounds the desired host count up to the nearest power of two, adds the required network- and broadcast-reservation addresses, and assigns the smallest possible prefix length. Sequential allocation keeps prefixes contiguous, easing later summarisation and access-control aggregation.

Core sizing formula:

where hosts is the required usable addresses. The resulting block size is 232 − prefixLen.

Colour cues in the utilisation badge mirror these bands so you can spot saturation instantly.

• Network address – dotted-decimal base of the parent block.
• Prefix length – slash notation value ( /n ) between 8 and 30.
• Hosts needed – positive integer for each planned subnet.
• Notes – optional free-text label stored with the subnet.

• All allocations are contiguous; gaps are not back-filled.
• Tool omits point-to-point /31 allocations by design.
• IPv6 addressing is out of scope IPv4 only.
• No overlap detection across separate parent blocks.

• Requesting hosts that exceed remaining space.
• Non-binary CIDR boundaries in imported lists.
• Manual edits to exported CSVs introducing invalid prefixes.
• Copy-paste of network addresses containing leading zeros.

Theory aligns with RFC 950 (Internet Subnetting), RFC 4632 (Classless Inter-Domain Routing), and numerous university networking curricula that validate VLSM efficiency over fixed-size schemes.

The planner processes only technical network data and stores nothing externally, so no personal-data regulations apply.

Step-by-Step Guide:

Follow these steps to draft and export a clean address-plan:

1. Enter the Network address of your parent block.
2. Select a Prefix that matches that block.
3. Type the required Hosts needed for the first subnet and click Add.
4. Repeat additions until the utilisation badge approaches your target capacity.
5. Verify no business-critical subnet exceeds 90 % utilisation before exporting.
6. Open the CSV or JSON tab and choose Copy or Download to integrate with inventory tools.

FAQ:

Glossary:

CIDR

Classless method for denoting network prefixes.

Prefix Length

Number of fixed network bits in an IPv4 address.

VLSM

Variable Length Subnet Masking; sizes subnets by need.

Broadcast Address

Last address in a subnet; used for one-to-all traffic.

Utilisation

Percentage of usable addresses already allocated.