Subnet Overlap Detector
Paste a list of IP networks in CIDR notation. The detector analyzes all pairs to find overlapping ranges, duplicate subnets, and embedded subsets. Perfect for VPC peering audits and VPN tunnel planning.
Enter CIDR Blocks
One per line. Comments after # are
ignored. Unprefixed IPs treated as /32.
Paste a list of CIDR blocks above and hit Detect Overlaps
to find duplicates and overlapping ranges.
Valid Subnets
0
Overlaps Found
0
Overlap Report
| Subnet A | Subnet B | Relationship | Explanation |
|---|
Why Subnet Overlaps Cause Outages
If two identical or overlapping subnets exist across a VPN tunnel or VPC Peering connection, traffic will be routed to the wrong destination or dropped.
Common Scenarios
- Cloud VPC Peering: AWS, Azure, and GCP block peering if CIDRs overlap.
- Site-to-Site IPsec: Duplicate RFC 1918 space requires complex Twice NAT.
- M&A: Internal address space almost always collides — an overlap audit is step one.