VPC & Subnet CIDR Overlap Checker
Paste multiple IPv4 CIDR blocks from AWS VPCs, Azure VNets, Kubernetes clusters, or office VPNs to detect address-space collisions before configuring VPC peering or Transit Gateways.
Collision Audit Verdict
Parsed Address Inventory (0 Subnets)
| Label / Source | Canonical CIDR | IPv4 Range | Total IPs | Status |
|---|
Why Auditing CIDR Overlaps Matters Before VPC Peering & Hybrid Routing
Cloud VPC peering connections (across AWS VPC Peering, AWS Transit Gateway, Azure VNet Peering, and Google Cloud Network Connectivity Center) require strictly non-overlapping RFC 1918 address blocks. If two environments both default to 10.0.0.0/16 or 172.17.0.0/16 (Docker's default bridge range), cloud control planes reject peering attachments outright—or worse, asymmetric routing silently blackholes return packets across IPsec and WireGuard tunnels.
Subtle collisions frequently hide across different prefix lengths: for example, a corporate WAN summary of 172.16.0.0/12 encompasses everything from 172.16.0.0 through 172.31.255.255, colliding with a seemingly distinct 172.24.4.0/22 branch network or Kubernetes serviceSubnet. Auditing integer start and end boundaries mathematically catches both partial intersections and nested containment before infrastructure is deployed.
If your audit reveals clean, adjacent subnets that can be consolidated into fewer firewall rules, pass your list directly into our CIDR Route Summarization Calculator.