CIDR Calculator
Calculate subnet ranges and network information for IP address analysis. Essential tool for network administrators and email infrastructure management.
Common Networks:
About CIDR Notation
Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and IP routing. CIDR notation represents an IP address and its associated network mask.
CIDR format: IP_ADDRESS/PREFIX_LENGTH (e.g., 192.168.1.0/24)
- /8 = 255.0.0.0 (16,777,214 usable hosts)
- /16 = 255.255.0.0 (65,534 usable hosts)
- /24 = 255.255.255.0 (254 usable hosts)
- /32 = 255.255.255.255 (single host)
Email infrastructure use: CIDR is commonly used for configuring mail server access controls, spam filters, and network-based authentication policies.