Calculator Input
Accepted formats: CIDR like 192.168.10.0/24, range like 192.168.10.1 - 192.168.10.200, or single IPv4 like 192.168.10.15.
Example Data Table
| Scenario | Input Blocks | Expected Summary | Why It Matters |
|---|---|---|---|
| Core VLAN Bundle | 10.10.0.0/24, 10.10.1.0/24, 10.10.2.0/24, 10.10.3.0/24 | 10.10.0.0/22 | Reduces four advertised routes to one route. |
| Branch Range Mix | 172.16.4.0/24, 172.16.5.20 - 172.16.5.200 | 172.16.4.0/23 | Shows overhead when inputs do not perfectly align. |
| Host Pair | 192.168.50.10, 192.168.50.11 | 192.168.50.10/31 | Useful for point-to-point planning with compact ranges. |
Formula Used
1) Normalize every input: Convert each CIDR, range, or host into a start IP and end IP. CIDR input becomes its network and broadcast pair.
2) Find total covered space: Sort the blocks, merge overlaps, then sum each merged interval length.
3) Find the common prefix: Compare the smallest covered IP and largest covered IP. The number of matching leading bits becomes the summary prefix.
4) Build the summary route: Summary network = minimum IP AND summary mask. Summary size = 2^(32 - prefix).
5) Measure overhead: Overhead addresses = summary addresses - covered addresses.
6) Efficiency: Aggregation efficiency = (covered addresses / summary addresses) × 100.
How to Use This Calculator
- Paste one IPv4 item per line in CIDR, range, or single-host format.
- Turn on strict boundary validation if you want aligned CIDR entries only.
- Choose how /31 networks should be interpreted for usable host counts.
- Submit the form to calculate the smallest summary route that covers every valid input.
- Review the summary CIDR, mask, wildcard, usable range, efficiency, and overhead addresses.
- Inspect normalized inputs and merged coverage blocks to confirm what was actually summarized.
- Use the graph to compare covered space, total summary space, and introduced overhead.
- Export the result to CSV or PDF for routing reviews, change plans, or documentation.
Frequently Asked Questions
1) What does an IP summary route do?
It combines multiple IPv4 blocks into one broader route. This reduces routing table size, simplifies advertisements, and can improve operational clarity when the included networks share a strong binary prefix.
2) Why can the calculator show overhead addresses?
A summary route must cover the entire binary span between the smallest and largest included addresses. If your inputs leave gaps, the summary still covers them, creating extra addresses that were not originally listed.
3) What is strict CIDR boundary validation?
It checks whether a CIDR entry starts exactly at its correct network address. For example, 192.168.1.12/24 is not aligned, while 192.168.1.0/24 is aligned and valid in strict mode.
4) Can I enter single IPv4 addresses?
Yes. When host parsing is enabled, each single IPv4 value is treated as a /32 block. That makes the tool useful for summarizing point addresses, firewall objects, and endpoint collections.
5) Why are merged coverage blocks shown separately?
Merged coverage blocks show the real occupied address space after overlaps and adjacency are combined. They help you see whether the data is contiguous or fragmented before the final summary route is applied.
6) Does one summary always mean a perfect aggregation?
No. One summary route may still include unused address space. A perfect aggregation happens only when the calculated summary contains exactly the listed space with no extra addresses added.
7) How is the summary prefix calculated?
The calculator compares the minimum and maximum covered IPv4 values in binary. The number of matching leading bits across both endpoints becomes the prefix length of the smallest enclosing supernet.
8) When is this calculator most useful?
It is useful during route design, BGP cleanup, firewall object consolidation, migration planning, address audits, and documentation work where you need compact route advertisements with quantified tradeoffs.