SubnetSentry

SubnetSentry is a web app (with optional desktop CLI) that validates and stress-tests subnet plans before you deploy them. You paste in proposed CIDRs/VLANs, cloud VPC subnets, on-prem ranges, and routing constraints; it then detects overlaps, wasted space, impossible summarization, and future-growth bottlenecks. It generates a clean IPAM-ready export (CSV/NetBox format), plus a “blast radius” report showing what breaks if you add a new site, peer a VPC, or extend a VPN. This is not a toy subnet calculator; it’s a pre-flight checker for real networks with guardrails and versioned change reviews. It also includes a lightweight policy engine (e.g., prod must be /24 or smaller, no shared RFC1918 blocks across regions) and produces human-readable change diffs for approvals. An AI assistant is optional for explaining findings, not for doing math.