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 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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