So IP subnet masks can be a bit tricky. Some IP’s are usable, some are not, and /24 is a different number than how many IP’s are available or even used. What I mean is for 100 IP’s why not go /100 seams easy enough lol. Well Computer programmers are infamous for making things harder than they need to be. I guess to scare off the easily timid. Luckily I found this really simple chart listing the translation for all the common Subnet masks.
| Net bits | Subnet mask | total-addresses per subnet |
|---|---|---|
| /20 | 255.255.240.0 | 4096 |
| /21 | 255.255.248.0 | 2048 |
| /22 | 255.255.252.0 | 1024 |
| /23 | 255.255.254.0 | 512 |
| /24 | 255.255.255.0 | 256 |
| /25 | 255.255.255.128 | 128 |
| /26 | 255.255.255.192 | 64 |
| /27 | 255.255.255.224 | 32 |
| /28 | 255.255.255.240 | 16 |
| /29 | 255.255.255.248 | 8 |
| /30 | 255.255.255.252 | 4 |