This is part of the Cisco Notes series on Mike’s World News.
I think one of the most important things to write down once you get into the testing center during the Cisco tutorial is your CIDR notation, with the # of hosts, and the full Subnet Mask. I would go from /22 – /30, although that is my personal preference.
| CIDR Notation | # of Hosts | Subnet Mask |
| /30 | 4 (2 usable) | 255.255.255.252 |
| /29 | 8 (6 usable) | 255.255.255.248 |
| /28 | 16 (14 usable) | 255.255.255.240 |
| /27 | 32 (30 usable) | 255.255.255.224 |
| /26 | 64 (62 usable) | 255.255.255.192 |
| /25 | 128 (126 usable) | 255.255.255.128 |
| /24 (Class C) | 256 (254 usable) | 255.255.255.0 |
| /23 | 512 (510 usable) | 255.255.254.0 |
| /22 | 1024 (1022 usable) | 255.255.252.0 |
| /21 | 2048 (2046 usable) | 255.255.248.0 |
| /20 | 4096 (4094 usable) | 255.255.240.0 |
| /19 | 8192 (8180 usable) | 255.255.224.0 |
| /18 | 16,384 (16,382 usable) | 255.255.192.0 |
| /17 | 32,768 (32,766 usable) | 255.255.128.0 |
| /16 (Class B) | 65,536 (65,534 usable) | 255.255.0.0 |
1 Comment
Excellent Cheat Sheet. Simple and Effective.