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IPv4 Subnet Cheat Sheet
|
CIDR |
Subnet Mask |
Total IPs |
Usable IPs |
| /32 | 255.255.255.255 | 1 | 1 |
| /31 | 255.255.255.254 | 2 | 2* |
| /30 | 255.255.255.252 | 4 | 2 |
| /29 | 255.255.255.248 | 8 | 6 |
| /28 | 255.255.255.240 | 16 | 14 |
| /27 | 255.255.255.224 | 32 | 30 |
| /26 | 255.255.255.192 | 64 | 62 |
| /25 | 255.255.255.128 | 128 | 126 |
| /24 | 255.255.255.0 | 256 | 254 |
| /23 | 255.255.254.0 | 512 | 510 |
| /22 | 255.255.252.0 | 1024 | 1022 |
| /21 | 255.255.248.0 | 2048 | 2046 |
| /20 | 255.255.240.0 | 4096 | 4094 |
| /19 | 255.255.224.0 | 8192 | 8190 |
| /18 | 255.255.192.0 | 16,384 | 16,382 |
| /17 | 255.255.128.0 | 32,768 | 32,766 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /15 | 255.254.0.0 | 131,072 | 131,070 |
| /14 | 255.252.0.0 | 262,144 | 262,142 |
| /13 | 255.248.0.0 | 524,288 | 524,286 |
| /12 | 255.240.0.0 | 1,048,576 | 1,048,574 |
| /11 | 255.224.0.0 | 2,097,152 | 2,097,150 |
| /10 | 255.192.0.0 | 4,194,304 | 4,194,302 |
| /9 | 255.128.0.0 | 8,388,608 | 8,388,606 |
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
| /7 | 254.0.0.0 | 33,554,432 | 33,554,430 |
| /6 | 252.0.0.0 | 67,108,864 | 67,108,862 |
| /5 | 248.0.0.0 | 134,217,728 | 134,217,726 |
| /4 | 240.0.0.0 | 268,435,456 | 268,435,454 |
| /3 | 224.0.0.0 | 536,870,912 | 536,870,910 |
| /2 | 192.0.0.0 | 1,073,741,824 | 1,073,741,822 |
| /1 | 128.0.0.0 | 2,147,483,648 | 2,147,483,646 |
Private IP ranges
| Class | Size | Subnet Mask | Range of IPs |
| Class A | 10.0.0.0/8 | 255.0.0.0 | 10.0.0.0 – 10.255.255.255 |
| Class B | 172.16.0.0/12 | 255.240.0.0 | 172.16.0.0 – 172.31.255.255 |
| Class C | 192.168.0.0/16 | 255.255.0.0 | 192.168.0.0 – 192.168.255.255 |
IPv6
|
Prefix |
/48s |
/56s |
/64s |
| /24 | 16M | 4G | 1T |
| /25 | 8M | 2G | 512G |
| /26 | 4M | 1G | 256G |
| /27 | 2M | 512M | 128G |
| /28 | 1M | 256M | 64G |
| /29 | 512K | 128M | 32G |
| /30 | 256K | 64M | 16G |
| /31 | 128K | 32M | 8G |
| /32 | 64K | 16M | 4G |
| /33 | 32K | 8M | 2G |
| /34 | 16K | 4M | 1G |
| /35 | 8K | 2M | 512M |
| /36 | 4K | 1M | 256M |
| /37 | 2K | 512K | 128M |
| /38 | 1K | 256K | 64M |
| /39 | 512 | 128K | 32M |
| /40 | 256 | 64K | 16M |
| /41 | 128 | 32K | 8M |
| /42 | 64 | 16K | 4M |
| /43 | 32 | 8K | 2M |
| /44 | 16 | 4K | 1M |
| /45 | 8 | 2K | 512K |
| /46 | 4 | 1K | 256K |
| /47 | 2 | 512 | 128K |
| /48 | 1 | 256 | 64K |
| /49 | 128 | 32K | |
| /50 | 64 | 16K | |
| /51 | 32 | 8K | |
| /52 | 16 | 4K | |
| /53 | 8 | 2K | |
| /54 | 4 | 1K | |
| /55 | 2 | 512 | |
| /56 | 1 | 256 | |
| /57 | 128 | ||
| /58 | 64 | ||
| /59 | 32 | ||
| /60 | 16 | ||
| /61 | 8 | ||
| /62 | 4 | ||
| /63 | 2 | ||
| /64 | 1 |
IPv6 bit mapping
Binary
| Bit | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Bit Value | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
Learning how to subnet is key to passing the CCNA, understanding how the internet works and the basis for any networking career.
You can practice with our IPv4 subnetting practice and IPv6 subnetting practice questions
You can verify your answers with our Subnet Calculator or VLSM Calculator.
If you want to learn more about networking and get the Cisco CCNA certification, we highly recommend the Cisco CCNA Gold Bootcamp as your CCNA training course. The CCNA is by far the most in-demand networking certification by employers, and the Gold Bootcamp is the highest rated Cisco course online. It has an average rating of 4.8 from over 30,000 public reviews:
