CIDR Aggregator
Accepts line-separated, comma-separated, or space-separated CIDRs.
6 valid CIDRs entered
How it works
What is CIDR aggregation? Also called supernetting or route summarization, it combines smaller prefixes into fewer larger blocks covering the same address space.
When to aggregate: ACL cleanup, BGP announcement summarization, IGP route summarization at area boundaries, and security audits where you need exact coverage visibility.
Aggregation rules:
- Two /24 blocks merge to /23 only when contiguous and aligned on an even /24 boundary.
- A /24 inside a /16 is redundant and disappears in aggregated output.
- Gaps break aggregation and force separate CIDRs.
Supernet vs subnet: subnetting splits one larger block into smaller ones; supernetting does the opposite and compresses many blocks into fewer larger ones.
Practical tips: always verify the final summary covers only intended ranges, run overlap checks before deployment, and document why aggregation was done.
FAQ
What is CIDR aggregation?
CIDR aggregation (supernetting, route summarization) combines multiple contiguous or overlapping CIDR blocks into the smallest possible set of supernets covering the same address space. It is the inverse of subnetting.
Why should I aggregate CIDRs?
Aggregation reduces entries in ACLs, route tables, and prefix lists. Fewer entries improve readability, reduce config size, and can reduce hardware pressure in TCAM or FIB resources.
Can non-adjacent CIDRs be aggregated?
Only when there are no gaps and the resulting block aligns to CIDR boundaries. If a gap exists, the CIDRs remain separate in output.
What happens to overlapping CIDRs?
Smaller CIDRs fully contained inside larger ones are absorbed by the larger block. No address space is lost.