IP range to CIDR notation

What is CIDR notation?

CIDR notation is a way to represent a subnet or interval of IP addresses in a compact format. It's written as an IP address followed by a slash and a number (e.g., 192.168.1.0/24). The number after the slash indicates the size of the network — a smaller number means more IP addresses (e.g., /24 = 256 addresses, /16 = 65,536 addresses). Sometimes an IP address range can't be represented as a single CIDR block, so it may be split into multiple CIDR blocks, as few as possible.

Input format

• Use format: start_ip - end_ip
• Example: 192.168.1.1 - 192.168.1.100
• Both addresses must be valid
• Start IP must be less than or equal to end IP

Use cases

• Network configuration
• Firewall rules configuration

Example conversions

• 192.168.1.0 - 192.168.1.255 → 192.168.1.0/24
• 10.0.0.1 - 10.0.0.10 → Multiple CIDR blocks

Compatibility

• Works with both IPv4 and IPv6