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CIDR Overlap Checker

Check whether two IPv4/IPv6 CIDR blocks overlap—runs entirely client-side.

Results

Processing…
Status
Processing...
Details
Processing...
Overlap?
Processing...
Family
Processing...
Overlap start
Processing...
Overlap end
Processing...

Rules & checks

Parses IPv4 and IPv6 CIDRs and requires the same family for both.

Computes overlap range when present.

Runs fully client-side/offline; no CIDRs leave the page.

When to use it

  • Avoid conflicting firewall or security group rules
  • Sanity-check overlapping VPC/VNET CIDRs before peering
  • Validate user-entered allowlists in admin panels

Tips

  • Keep both CIDRs in the same protocol (IPv4 or IPv6)
  • Normalize CIDRs to reduce accidental overlaps

Examples

Overlap

  • 10.0.0.0/24 vs 10.0.0.128/25 -> overlap

No overlap

  • 10.0.0.0/24 vs 10.0.1.0/24 -> no overlap

IPv6 overlap

  • 2001:db8::/64 vs 2001:db8::/65 -> overlap

FAQs

Is any data stored or sent?
No. Everything runs locally and clears on refresh.
Can I compare more than two?
Compare pairs here; for bulk overlap use multiple checks.

Related validators

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CIDR Validator

Validate IPv4/IPv6 CIDR blocks and view the normalized network address.

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IP Range Validator

Validate start/end IP ranges (IPv4 or IPv6) and check ordering.

Format-only; does not test reachability or routing behavior.