Calculator Inputs
Example Data Table
| Scenario | Input Blocks | Expected Supernet | Why It Works |
|---|---|---|---|
| Four contiguous /24 routes | 192.168.0.0/24 to 192.168.3.0/24 | 192.168.0.0/22 | Four adjacent /24 networks fill one /22 exactly. |
| Two contiguous /25 routes | 10.10.10.0/25 and 10.10.10.128/25 | 10.10.10.0/24 | Both halves of the /24 are present. |
| Non-exact covering summary | 172.16.0.0/24 and 172.16.2.0/24 | 172.16.0.0/22 | The /22 covers both blocks, but leaves a gap. |
Formula Used
1. Normalize every block: Network Address = IP Address AND Subnet Mask.
2. Find the coverage range: Lowest network start and highest broadcast end define the full address span.
3. Compute the common prefix: Supernet Prefix = number of identical leading bits shared by the lowest start and highest end.
4. Build the summarized mask: Subnet Mask = (232 - 1) << (32 - prefix).
5. Count addresses: Address Count = 232 - prefix.
6. Check exactness: Exact aggregation is true only when the merged input coverage fills the summarized block completely, without gaps or overlaps.
How to Use This Calculator
- Enter at least two IPv4 CIDR blocks.
- Choose whether you want the smallest covering supernet or exact-only validation.
- Select delimiter handling if your list uses commas or line breaks.
- Choose whether duplicate networks should be skipped.
- Enable binary details if you want bit-level verification.
- Click Calculate Supernet to place the results above the form.
- Review the summary table, route reduction, gaps, overlaps, and chart.
- Use the CSV and PDF buttons to export your results.
Frequently Asked Questions
1) What is supernetting?
Supernetting combines multiple smaller CIDR routes into one larger summarized route. It helps reduce routing table size, simplifies advertisements, and can improve operational clarity when networks are contiguous and align correctly.
2) When is exact aggregation possible?
Exact aggregation works when the supplied ranges form one continuous block and fully occupy the summarized network. No gaps, overlaps, or missing halves can exist inside the resulting supernet.
3) Why does the calculator sometimes add extra addresses?
The smallest covering supernet may include unused address space when your inputs are not perfectly aligned. That larger block still covers every input network, but it is not an exact fill.
4) Can I mix different prefix lengths?
Yes. The calculator accepts mixed IPv4 prefixes such as /24, /25, and /26. It normalizes them, compares the full ranges, and then computes the smallest summarized block.
5) Does input order matter?
No. The calculator sorts networks internally before analyzing them. You can paste routes in any order, and the computed coverage, gaps, and summary remain the same.
6) How are overlaps and duplicates handled?
Overlaps are flagged in the results because they distort exact aggregation. Duplicate routes can either be removed automatically or kept, depending on the duplicate handling option you choose.
7) Does this calculator support IPv6?
No. This version is focused on IPv4 CIDR supernetting. IPv6 summarization uses similar ideas, but the address format and binary width require a different implementation.
8) Why show usable hosts in a routing calculator?
Usable host counts help planning teams understand the operational size of a summarized block. It is useful when route design, address allocation, and documentation happen together.