Verified Developer Solution • 100% OfflineFix "Invalid CIDR notation" / Invalid subnet mask
Troubleshoot network configuration errors caused by out-of-bounds CIDR block definitions.
Your cloud provider (AWS, GCP) or network script rejects your IP range with "Invalid CIDR notation". This happens when the routing prefix exceeds /32 for IPv4, or if the base IP address is not the actual network address for the given mask.
Ensure your suffix is between /0 and /32. Also ensure that the host bits are zeroed out. For example, `192.168.1.5/24` is technically invalid as a network definition; it should be `192.168.1.0/24`.
Code Standard: Bad Pattern vs Verified Fix
Live Syntax1# ❌ Bad: Base IP has host bits set2allow_ip = "10.0.0.5/24"3 4# ✅ Good: Base IP is the network boundary5allow_ip = "10.0.0.0/24"Test and resolve this using CIDR Calculator & Subnet Inspector
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Frequently Asked Questions
Q:What does the /24 mean?
It means the first 24 bits of the IP address are fixed (the network), leaving 8 bits (256 addresses) for hosts.
Q:How do I calculate the correct base IP?
Use our CIDR Calculator to instantly determine the network address, broadcast address, and valid host ranges.