CIDR Overlap & Contains Checker
Check if subnets overlap or if an IP belongs to a CIDR block.
About this tool
Compare two IPv4 CIDR blocks for overlap — essential for VPC peering, firewall rules, and route planning. Also test whether a host IP falls inside a network.
What you get
- Overlap yes/no with shared address range
- Whether an IP is inside a CIDR block
- Normalized network bounds for each input
How to use
Enter two CIDRs to test overlap, or one CIDR plus an IP for membership. Results update as you type.
FAQ
How to check if two subnets overlap?
Enter two IPv4 CIDR blocks and read whether their address ranges intersect, plus the shared range when they do.
How to test if an IP is in a CIDR range?
Provide one CIDR and a host IP to see membership yes/no with normalized network bounds.
Why do overlapping subnets cause routing problems?
Overlapping ranges make it ambiguous which path should carry traffic, breaking VPC peering, firewall rules, and static routes.
How to find the shared range of two CIDR blocks?
When overlap is detected, the tool reports the intersecting address span so you can redesign allocations.
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