Subnet Mask Information
Have you taken a TCP/IP class? Yes, I did a long time ago. Learning TCP/IP and the OSI Model has been the eye-opener for me that really took my consulting career to the next level. I spent a week in class and learned all the binary math to figure out which subnet mask to use that would be most efficient for a network. This was great knowledge and I am good at math, but who wants to write all that math down?That’s why we have calculators and cheat sheets!Sometimes I just need to know quickly what a /18 is. I mean, I know most of the standard network codes by heart, but when working on a big project it helps to know all of them. Here is a quick Subnet Mask Cheat Sheet so I don’t have to go to some other website anymore.Subnet Mask Cheat Sheet
| Subnet Mask | Hosts | |
|---|---|---|
| /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 | 255.255.255.0 | 256 |
| /23 | 255.255.254.0 | 512 |
| /22 | 255.255.252.0 | 1024 |
| /21 | 255.255.248.0 | 2048 |
| /20 | 255.255.240.0 | 4096 |
| /19 | 255.255.224.0 | 8192 |
| /18 | 255.255.192.0 | 16384 |
| /17 | 255.255.128.0 | 32768 |
| /16 | 255.255.0.0 | 65536 |
