CIDR Aggregator
Collapse a mixed list of IPv4 addresses, ranges, and CIDR blocks into the minimal equivalent CIDR set. Ideal for cleaning up firewall rules, route tables, and BGP prefix lists.
Paste input and click Aggregate.
What is CIDR Aggregation?
CIDR aggregation (also called route summarization or supernetting) is the process of merging multiple adjacent or overlapping IP prefixes into the fewest possible CIDR blocks. Network engineers use it to shrink firewall ACLs, simplify static route tables, and reduce the size of BGP advertisements.
For example, 10.0.0.0/24 and 10.0.1.0/24 together cover exactly the same addresses as 10.0.0.0/23. Three rules become one. On a large router or firewall, the savings add up to faster lookups and easier audits.
Accepted Input Formats
- CIDR:
10.0.0.0/24 - Single IP:
10.0.0.5(treated as/32) - Range:
10.0.0.0-10.0.0.50or10.0.0.0 - 10.0.0.50 - Mixed input is fine. Comments after
#and blank lines are ignored.
How It Works
- Every input is parsed into a numeric [start, end] range.
- Ranges are sorted by start address and merged where they touch or overlap.
- Each merged range is split into the smallest possible set of properly aligned CIDR blocks.
Use Cases
- Firewall ACL cleanup — collapse hundreds of
/32allow-list entries - BGP prefix lists — reduce announced prefix count
- Route table optimization — fewer routes, faster longest-prefix match
- Cloud security groups — AWS/GCP/Azure all have rule-count limits
- Geo-IP / CDN allowlists — vendors often publish thousands of ranges; aggregate before deploying
Frequently Asked Questions
Any mix of single IPv4 addresses (
10.0.0.5), CIDR blocks (10.0.0.0/24), and ranges (10.0.0.0-10.0.0.255 or 10.0.0.0 - 10.0.0.255). One entry per line, or comma/space separated. Comments after # are ignored.All inputs are normalized to numeric ranges, sorted, and merged. The merged ranges are then split into the smallest possible set of CIDR blocks where each block is properly aligned (network address is a multiple of its size). The output is always equivalent to the input — it covers the exact same IPs, just expressed more compactly.
A CIDR block can only represent a contiguous, power-of-two-sized, properly aligned range. For example,
10.0.0.0 to 10.0.0.10 (11 addresses) cannot be expressed as one CIDR — it needs several. The aggregator picks the minimal valid set.Not yet — this tool is IPv4-only. IPv6 aggregation works on the same principles but requires 128-bit arithmetic (BigInt). If you need IPv6 aggregation, let us know via the contact page.
No. All parsing, merging, and CIDR computation runs in your browser. The IP list never leaves your machine.