Fix AWS VPC & Terraform Error: 'is not a valid CIDR block; did you mean...' (Host Bits Set)
Calculate exact IPv4 network boundary addresses and AWS 5-reserved-IP subnet masks using `npx castov cidr`.
Error: "10.24.1.5/24" is not a valid CIDR block: host bits are set (did you mean "10.24.1.0/24"?)
# Calculate exact network address, broadcast address, and AWS usable hosts locally: npx castov cidr 10.24.0.0/22 --json # Or ask Claude/Cursor using Castov MCP tool: castov_cidr
Root Cause & Mechanism Analysis
Why does this error occur?
A CIDR block specification must use the exact base network address where all host bits after the prefix length are zero (e.g., `10.24.0.0/22`, not `10.24.1.0/22`).
Frequently Asked Questions
How many IP addresses does AWS reserve in every VPC subnet?
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