Random CIDR Block Generator
CIDR blocks are generated locally in your browser with the Web Crypto API. Values stay on your device.
Documentation-safe network fixtures
Generate CIDR blocks from RFC 5737 IPv4 ranges (192.0.2.0/24, 198.51.100.0/24, and 203.0.113.0/24) or the 2001:db8::/32 IPv6 range for firewall rules, allowlists, mock API payloads, seed data, and tests.
Each result uses a valid network address for the selected prefix. This generator does not calculate ranges or return real routable networks.