Exact CIDR Aggregator
Merge prefixes without adding addresses.
Exact CIDR Aggregator: inputs and results
Enter an IP address, CIDR prefix, or range. Then check its first and last address below.
Calculated Boundaries & ParametersReady
Key Capabilities
- •100% Client-Side: Zero telemetry or server latency.
- •RFC Compliant: Exact 32-bit and 128-bit integer precision.
- •Quick Copy: Instant access to CIDR, mask, and range bounds.
- •Cross-Platform: Works on desktop, tablet, and mobile browsers.
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How Exact CIDR Aggregator Works?
The Exact CIDR Aggregator works by merging overlapping and adjacent prefixes into intervals, then converting each interval back into the fewest CIDR blocks that cover exactly the same addresses.
Paste the prefixes
Enter a list such as
10.0.0.0/24,10.0.1.0/24,10.0.2.0/23.Merge into intervals
Overlapping and touching prefixes join into continuous ranges.
Re-cut into CIDR blocks
Each range becomes the minimal aligned CIDR list.
Confirm exactness
The address count before and after is identical, so no new address is added.
Exact CIDR Aggregator Formula
The Exact CIDR Aggregator formula is Output = CIDR(merge(Input)), with |Output addresses| = |Input addresses|.
Merge step
join when S_next ≤ E_cur + 1Removes overlaps and gaps of 0.
CIDR step
largest aligned block that fits, repeatedExact cover of each range.
Exactness
Σ out = |∪ in|No address added or removed.
Worked example: 4 prefixes
Input : 10.0.0.0/24, 10.0.1.0/24, 10.0.2.0/23, 10.0.4.0/25 Output : 10.0.0.0/22, 10.0.4.0/25 Size : 1,152 addresses before and after
Exact CIDR Aggregator Conversion Table
The Exact CIDR Aggregator conversion table aggregates 7 prefix lists without adding any address.
| Input Prefixes | Aggregated Output | Entries Before | Entries After |
|---|---|---|---|
| 10.0.0.0/24, 10.0.1.0/24, 10.0.2.0/23, 10.0.4.0/25 | 10.0.0.0/22, 10.0.4.0/25 | 4 | 2 |
| 192.168.0.0/25, 192.168.0.128/25 | 192.168.0.0/24 | 2 | 1 |
| 192.168.1.0/24, 192.168.2.0/24 | 192.168.1.0/24, 192.168.2.0/24 | 2 | 2 |
| 172.16.0.0/16, 172.16.5.0/24, 172.17.0.0/16 | 172.16.0.0/15 | 3 | 1 |
| 203.0.113.0/26, 203.0.113.64/26, 203.0.113.128/25 | 203.0.113.0/24 | 3 | 1 |
| 10.10.0.0/24, 10.10.0.0/24, 10.10.1.0/24 | 10.10.0.0/23 | 3 | 1 |
| 198.51.100.0/27, 198.51.100.64/27 | 198.51.100.0/27, 198.51.100.64/27 | 2 | 2 |
What is Exact CIDR Aggregator?
The Exact CIDR Aggregator is a tool that combines a list of CIDR prefixes into the shortest equivalent list without adding a single address.
Route summarization often trades accuracy for size and covers addresses that were never in the list. Exact aggregation never does. 192.168.1.0/24 and 192.168.2.0/24 stay as 2 entries, since the only single prefix covering both, a /22, adds 512 addresses.
Exact aggregation is the safe choice for security rules, where an extra address is an extra exposure.
What are the uses of Exact CIDR Aggregator?
There are 4 main uses of the Exact CIDR Aggregator, including firewall object reduction, prefix list cleanup, and allow-list compaction.
Reducing firewall objects
Fewer entries mean faster rule evaluation and simpler reviews.
Cleaning BGP prefix lists
Prefix lists shrink without accepting new announcements.
Compacting cloud allow-lists
Security groups with a 60-rule limit hold more networks after aggregation.
Deduplicating provider ranges
Published provider lists often contain nested prefixes that collapse away.