Calculate CIDR blocks and IP ranges. Convert between CIDR notation and start/end IP addresses. Plan subnets for network architecture.
| CIDR | Subnet Mask | IPs | Class |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | A |
| /12 | 255.240.0.0 | 1,048,576 | - |
| /16 | 255.255.0.0 | 65,536 | B |
| /20 | 255.255.240.0 | 4,096 | - |
| /24 | 255.255.255.0 | 256 | C |
| /28 | 255.255.255.240 | 16 | - |
| /30 | 255.255.255.252 | 4 | - |
| /32 | 255.255.255.255 | 1 | Host |
CIDR (Classless Inter-Domain Routing) is a method for allocating IP addresses more efficiently than the old class-based system. CIDR notation (e.g., 10.0.0.0/16) combines an IP address with a prefix length that indicates how many bits define the network portion.