IPv4 Allocation Planner

Introduction:

IPv4 subnets are contiguous address ranges that group devices and control reachability. A clear plan shows how many addresses each segment needs and how those segments fit inside a chosen parent range.

You provide a network address and a prefix, then list the host counts you intend to serve, and the planner proposes aligned ranges with the first and last usable addresses so you can assign space without overlaps.

For example, starting from 10.0.0.0 with prefix 24 and asking for 50 hosts returns a 10.0.0.0 slash 26 block that offers 62 usable addresses and leaves the rest available for later groups.

Valid formats confirm structure only, not reachability or entitlement, so double check routes and avoid mixing sensitive notes with production secrets. Planning largest segments first often reduces gaps and keeps utilisation tidy.

Technical Details:

The planner models IPv4 address space as 32 discrete bits and summarises segments by prefix length. It reports the network address, broadcast address, first and last usable address, and the count of usable host addresses inside each proposed block.

From a requested host count, it calculates the smallest power‑of‑two block that can contain those hosts and aligns that block within the parent range. Special handling applies to two cases where usable host addressing differs from the typical network and broadcast pattern.

Results reflect exact binary boundaries. Crossing a boundary increases the block size to the next power of two, so asking for only one more host can double the space consumed, which is expected behaviour for aligned ranges.

Comparisons are meaningful within the same parent range. The utilisation figure is the sum of usable addresses in planned blocks divided by the usable addresses in the parent range, rounded to the nearest whole percent.

1. Start at the parent network address.
2. For each request, compute p from N using the equations above.
3. Align to the next block boundary within the parent.
4. Emit network, first, last, broadcast, and usable counts.
5. Advance the starting point to the end of the last allocation.

Units, precision, and rounding.

• All addresses are exact integers; no floating‑point arithmetic is used.
• Percent utilisation is rounded to the nearest integer percent.

Networking and storage behaviour.

• All calculations happen locally in the UI layer.
• Clipboard copy and file downloads are performed by the device using in‑memory blobs.
• No requests to remote services are made by the planner.

Diagnostics and determinism.

• Identical inputs yield identical allocations.
• Allocations append in order; removing earlier rows does not repack prior blocks.
• Errors surface as a toast message when space is insufficient.

Assumptions and limitations.

• Heads‑up IPv4 only; no IPv6 support.
• Heads‑up Parent prefix selection is limited to /8 to /31.
• Blocks are powers of two and boundary‑aligned by design.
• Two special cases: /31 yields two usable addresses; /32 yields one.
• Planner advances from the last allocated address; it does not back‑fill gaps.
• CSV reflects visible columns only; hidden fields are omitted.
• CSV fields are not quoted; commas in notes will create extra columns.
• Filter matches on the raw row content stringified to text.

Edge cases and error sources.

• Octets outside 0 to 255 invalidate the network address.
• Non‑integer host entries are rejected; minimum is 1.
• Requests that exceed remaining space raise an error.
• Asking for 3 hosts consumes a /30 block with 2 reserved addresses.
• Percent utilisation may jump as blocks cross power‑of‑two thresholds.
• Deleting a middle block leaves a gap until you clear or re‑plan.
• Clipboard permissions may block copying depending on device policy.
• Empty exports occur if all columns are hidden.
• Whitespace is trimmed on key text inputs; invisible characters may still affect matching.
• Very large plans can be cumbersome to scan without filtering.

Privacy and compliance.

No data is transmitted or stored server‑side. Avoid including sensitive production identifiers in notes.

How‑to Guide:

Subnet planning from host counts and a parent range.

1. Enter the network address and choose a prefix.
2. Add a host count and optional notes, then select Add.
3. Repeat for additional groups; larger groups first to minimise fragmentation.
4. Toggle columns to show network, first, last, broadcast, or notes as needed.
5. Use the filter box to locate entries quickly.
6. Copy or download CSV or JSON when the plan is ready.

• Plan biggest segments first to conserve contiguous space.
• Record VLAN, site, or service tags in notes to aid audits.

FAQ:

Troubleshooting:

• “Invalid address” — check each octet is between 0 and 255.
• “Invalid prefix” — choose a value from 8 to 31.
• “Not enough space for that subnet” — reduce the request or clear earlier blocks.
• Copy fails — allow clipboard access for the page.
• Empty CSV/JSON — ensure at least one column is visible.
• Unexpected columns in CSV — remove commas from notes or tidy in a spreadsheet.

Advanced Tips:

• Tip Add largest subnets first to minimise fragmentation.
• Tip Use /31 for point to point links when appropriate.
• Tip Keep notes consistent to make filtering fast and reliable.
• Tip Hide columns you do not need before exporting.
• Tip Use the filter to isolate a VLAN, service, or site tag.
• Tip Reuse the parent range across scenarios to compare utilisation.

Glossary:

IPv4 address

A 32‑bit identifier written as four decimal octets.

Subnet

A contiguous range of addresses within a larger network.

Prefix length

The number of leading bits that define the network portion.

Network address

The first address in a block that identifies the subnet itself.

Broadcast address

The last address in a block used to reach all hosts in it.

Usable addresses

Addresses assignable to hosts in a subnet.

CIDR

Classless Inter‑Domain Routing representation of networks.