Calculator
Example Data Table
| Input CIDRs | Exact Aggregated Output | Why It Aggregates |
|---|---|---|
| 10.0.0.0/24 + 10.0.1.0/24 | 10.0.0.0/23 | Two adjacent /24 blocks align perfectly into one /23. |
| 172.16.0.0/24 + 172.16.1.0/24 + 172.16.2.0/24 + 172.16.3.0/24 | 172.16.0.0/22 | Four aligned /24 networks form a single summarized /22. |
| 192.168.8.0/24 + 192.168.10.0/24 | 192.168.8.0/24 and 192.168.10.0/24 | A gap prevents safe summarization into one exact route. |
| 10.10.0.0/23 + 10.10.1.0/24 | 10.10.0.0/23 | The smaller network is already covered by the broader route. |
Formula Used
The calculator converts every CIDR block into an integer start and end address range. It then merges overlaps, optionally merges touching ranges, and converts the final exact ranges back into the fewest valid CIDR blocks.
- Block size:
2^(32 - prefix) - Network start:
floor(IP / block size) × block size - Broadcast end:
network start + block size - 1 - Exact summarization rule: choose the largest aligned block that never crosses the merged interval end.
This method preserves exact address coverage. It does not force one larger supernet unless that supernet matches the merged coverage or is shown separately as a broader covering summary.
How to Use This Calculator
- Paste IPv4 CIDR entries into the input box, one per line or separated by commas.
- Choose whether contiguous ranges should merge, and whether duplicates should be removed.
- Decide whether host-bit entries should be normalized automatically or rejected.
- Submit the form to see aggregated routes above the calculator.
- Review the summary cards, covering supernet, data tables, and Plotly graph.
- Download the aggregated table as CSV or PDF for routing documentation.
FAQs
1. What does CIDR aggregation do?
CIDR aggregation combines multiple routes into fewer summarized routes when alignment and coverage rules allow it. This reduces routing table size and can simplify advertisement policies.
2. Does this tool support exact coverage?
Yes. The main output preserves exact covered addresses after overlap handling. It only creates larger blocks when those blocks still match the merged address span exactly.
3. Why are some networks not merged?
Some networks may be adjacent but not properly aligned for a safe supernet. Others may have gaps between them. In both cases, the calculator keeps separate aggregated blocks.
4. What happens when host bits are set?
You can normalize them automatically or reject them. Automatic normalization converts entries like 10.0.0.5/24 into the canonical network 10.0.0.0/24.
5. Why show a covering supernet separately?
A covering supernet is helpful for planning or visual review. It spans the full start-to-end range, but it may include extra addresses that the exact aggregation does not actually cover.
6. Can overlaps reduce route count automatically?
Yes. When one route is fully inside another, the exact coverage already includes it. The calculator removes redundant coverage before producing final summarized blocks.
7. Is this calculator suitable for IPv6?
No. This version is designed for IPv4 CIDR notation only. IPv6 aggregation needs a separate parser and larger integer handling for 128-bit addresses.
8. What do the CSV and PDF exports include?
They export the aggregated output table, including CIDR, netmask, wildcard, host range, broadcast, address count, and binary details when enabled in the results.