Subnet Overlap Detector
Identify collisions and containment between CIDR blocks. Paste a list of subnets to find which ones overlap, helping you prevent routing conflicts and firewall rule shadowing.
Input CIDR Blocks
Paste a list of IPv4 subnets above to check for overlaps and containment.
Why check for subnet overlaps?
Overlapping subnets cause major issues in enterprise networks. They can lead to non-deterministic routing, where traffic for a specific destination might be sent to different gateways depending on where it originates. In firewall configuration, overlapping blocks can lead to rule shadowing, where a broader rule inadvertently blocks or permits traffic meant for a more specific subnet.