In every subnet, the first available IP address is used for the network address, and the last available IP address is used for the broadcast address. The remaining available IP addresses are used for the hosts in the subnet. For this reason, the number of useable IP addresses is the number of available IP addresses minus 2.
The three most commonly used prefixes are:
- /8
- /16
- /24
Or like this
- x.[0-255].[0-255].[0-255]/8
- x.x.[0-255].[0-255]/16
- x.x.x.[0-255]/24
With /8, the first item in the IP address is used for the subnet (typically 10.) and the last three items are used for the network IP (typically 10.0.0.0), broadcast IP (typically 10.255.255.255) and host machines.
With /16, the first two items in the IP address are used for the subnet (typically 172.16) and third and fourth items are used for the network IP (typically 172.16.0.0), broadcast IP (typically 172.16.255.255) and host machines.
With /24, the first three items in the IP address are used for the subnet (typically 192.168.0) and the fourth item is the range of IP addresses used for the network IP (typically 192.168.0.0), broadcast IP (typically 192.168.0.255), and host machines.
| Subnet Mask | Prefix | Number of available IP addresses per subnet | Network IP | First Available IP Address | Last Available IP Address | Broadcast IP | Number of subnets |
|---|---|---|---|---|---|---|---|
| 255.255.255.255 | /32 | 0 | 16,777,216 | ||||
| 255.255.255.254 | /31 | 2 | 8,388,608 | ||||
| 255.255.255.252 | /30 | 4 | 4,194,304 | ||||
| 255.255.255.248 | /29 | 8 | 2,097,152 | ||||
| 255.255.255.240 | /28 | 16 | 1,048,576 | ||||
| 255.255.255.224 | /27 | 32 | 524,288 | ||||
| 255.255.255.192 | /26 | 64 | 262,144 | ||||
| 255.255.255.128 | /25 | 128 | 131,072 | ||||
| 255.255.255.0 |
10.0.0.0/24 192.168.0.0/24 |
256 |
10.0.0.0 192.168.0.0 |
10.0.0.1 192.168.0.1 |
10.0.0.254 192.168.0.254 |
10.0.0.255 192.168.0.255 |
65,536 |
| 255.255.254.0 | /23 | 512 | 32,768 | ||||
| 255.255.252.0 | /22 | 1,024 | 16,384 | ||||
| 255.255.248.0 | /21 | 2,048 | 8,192 | ||||
| 255.255.240.0 | /20 | 4,096 |
172.31.0.0 172.31.16.0 172.31.32.0 |
172.31.0.1 172.31.16.1 172.31.32.1 |
172.31.15.254 172.31.31.254 172.31.47.254 |
172.31.15.255 172.31.31.255 172.31.47.255 |
4,096 |
| 255.255.224.0 | /19 | 8,192 | 2,048 | ||||
| 255.255.192.0 | /18 | 16,384 | 1,024 | ||||
| 255.255.128.0 |
10.0.0.0/17 192.168.0.0/17 |
32,768 |
10.0.0.0 192.168.0.0 |
10.0.0.1 192.168.0.1 |
10.0.127.254 192.168.127.254 |
10.0.127.255 192.168.127.255 |
512 |
| 255.255.0.0 |
10.0.0.0/16 172.16.0.0/16 192.168.0.0/16 |
65,536 |
10.0.0.0 172.16.0.0 192.168.0.0 |
10.0.0.1 172.16.0.1 192.168.0.1 |
10.0.255.254 172.16.255.254 192.168.255.254 |
10.0.255.255 172.16.255.255 192.168.255.255 |
256 |
| 255.254.0.0 | /15 | 131,072 | 128 | ||||
| 255.252.0.0 | /14 | 262,144 | 64 | ||||
| 255.248.0.0 | /13 | 524,288 | 32 | ||||
| 255.240.0.0 | /12 | 1,048,576 | 16 | ||||
| 255.224.0.0 | /11 | 2,097,152 | 8 | ||||
| 255.192.0.0 | /10 | 4,194,304 | 4 | ||||
| 255.128.0.0 | /9 | 8,388,608 | 2 | ||||
| 255.0.0.0 |
10.0.0.0/8 |
16,777,216 |
10.0.0.0 |
10.0.0.1 |
10.255.255.254 |
10.255.255.255 |
0 |
Did you find this article helpful?
If so, consider buying me a coffee over at 