This blog post provides a quick reference table for CIDR notation, subnet masks, and host counts, making it a valuable tool for tasks like configuring security groups, firewall rules, and subnetting. It simplifies network planning and ensures accurate IP address allocation for efficient and secure network setups.
CIDR Reference Table
| CIDR Prefix Length | Netmask | Hosts (Class C’s/B’s/A’s) |
| /32 | 255.255.255.255 | 1 |
| /31 | 255.255.255.254 | 2 |
| /30 | 255.255.255.252 | 4 |
| /29 | 255.255.255.248 | 8 |
| /28 | 255.255.255.240 | 16 |
| /27 | 255.255.255.224 | 32 |
| /26 | 255.255.255.192 | 64 |
| /25 | 255.255.255.128 | 128 |
| /24 (Class C) | 255.255.255.0 | 256 / 1 |
| /23 | 255.255.254.0 | 512 / 2 |
| /22 | 255.255.252.0 | 1,024 / 4 |
| /21 | 255.255.248.0 | 2,048 / 8 |
| /20 | 255.255.240.0 | 4,096 / 16 |
| /19 | 255.255.224.0 | 8,192 / 32 |
| /18 | 255.255.192.0 | 16,384 / 64 |
| /17 | 255.255.128.0 | 32,768 / 128 |
| /16 (Class B) | 255.255.0.0 | 65,536 / 256 / 1 |
| /15 | 255.254.0.0 | 131,072 / 512 / 2 |
| /14 | 255.252.0.0 | 262,144 / 1024 / 4 |
| /13 | 255.248.0.0 | 524,288 / 2048 / 8 |
| /12 | 255.240.0.0 | 1,048,576 / 4096 / 16 |
| /11 | 255.224.0.0 | 2,097,152 / 8129 / 32 |
| /10 | 255.192.0.0 | 4,194,304 / 16,384 / 64 |
| /9 | 255.128.0.0 | 8,388,608 / 32,768 / 128 |
| /8 (Class A) | 255.0.0.0 | 16,777,216 / 65,536 / 256 / 1 |
| /7 | 254.0.0.0 | 33,554,432 / 131,072 / 512 / 2 |
| /6 | 252.0.0.0 | 67,108,864 / 262,144 / 1,024 / 4 |
| /5 | 248.0.0.0 | 134,217,728 / 524,288 / 2,048 / 8 |
| /4 | 240.0.0.0 | 268,435,456 / 1,048,576 / 4,096 / 16 |
| /3 | 224.0.0.0 | 536,870,912 / 2,097,152 / 8,192 / 32 |
| /2 | 192.0.0.0 | 1,073,741,824 / 4,194,304 / 16,384 / 64 |
| /1 | 128.0.0.0 | 2,147,483,648 / 8,388,608 / 32,768 / 128 |
| /0 | 0.0.0.0 | 4,294,967,296 / 16,777,216 / 65,536 / 256 |
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