CIDR Aggregator - Free Online Tool
CIDR Aggregator
Merge Multiple CIDR Blocks into the Fewest Supernets
Understanding CIDR Aggregation
Route Summarization
Network engineers aggregate many small routes into fewer, larger ones to reduce the size of routing tables.
Simplified Firewall Rules
Merge a long list of allowlisted CIDR blocks into the fewest rules a firewall or security group needs.
Overlap Resolution
Automatically handles overlapping or adjacent input blocks without double-counting their coverage.
Client-Side Only
All calculation happens locally in your browser — no data is ever sent to a server.
How Aggregation Works
This tool first converts each CIDR block into its numeric start-end address range, merges any ranges that are adjacent or overlapping, then re-splits each merged range back into the minimal set of CIDR-aligned blocks needed to cover it exactly — the same two-step process used internally by route summarization algorithms in real routers.
Key Takeaways
- Handles Overlaps: Input blocks that overlap or are adjacent are merged correctly without duplicating coverage.
- Minimal Output: Produces the smallest possible set of CIDR blocks that exactly covers your input.
- Client-Side Only: All calculation happens locally in your browser — no data is ever sent to a server.