It stuff: CIDR masks and subnets table
Below is a table providing typical subnets for IPv4.
| Prefix size |
Network mask |
Usable hosts per subnet |
| /1 |
128.0.0.0 |
2,147,483,646 |
| /2 |
192.0.0.0 |
1,073,741,822 |
| /3 |
224.0.0.0 |
536,870,910 |
| /4 |
240.0.0.0 |
268,435,454 |
| /5 |
248.0.0.0 |
134,217,726 |
| /6 |
252.0.0.0 |
67,108,862 |
| /7 |
254.0.0.0 |
33,554,430 |
| Class A |
no data |
no data |
| /8 |
255.0.0.0 |
16,777,214 |
| /9 |
255.128.0.0 |
8,388,606 |
| /10 |
255.192.0.0 |
4,194,302 |
| /11 |
255.224.0.0 |
2,097,150 |
| /12 |
255.240.0.0 |
1,048,574 |
| /13 |
255.248.0.0 |
524,286 |
| /14 |
255.252.0.0 |
262,142 |
| /15 |
255.254.0.0 |
131,070 |
| Class B |
no data |
no data |
| /16 |
255.255.0.0 |
65,534 |
| /17 |
255.255.128.0 |
32,766 |
| /18 |
255.255.192.0 |
16,382 |
| /19 |
255.255.224.0 |
8,190 |
| /20 |
255.255.240.0 |
4,094 |
| /21 |
255.255.248.0 |
2,046 |
| /22 |
255.255.252.0 |
1,022 |
| /23 |
255.255.254.0 |
510 |
| Class C |
no data |
no data |
| /24 |
255.255.255.0 |
254 |
| /25 |
255.255.255.128 |
126 |
| /26 |
255.255.255.192 |
62 |
| /27 |
255.255.255.224 |
30 |
| /28 |
255.255.255.240 |
14 |
| /29 |
255.255.255.248 |
6 |
| /30 |
255.255.255.252 |
2 |
| /31 |
255.255.255.254 |
no data |
| /32 |
255.255.255.255 |
no data |
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