切分表
172.16.0.0/16 切成 /20
借 4 位，16 个子网，每个 4,094 台可用主机。
- 原网段
- 172.16.0.0/16
- 新掩码
- 255.255.240.0
- 子网个数
- 16（2 的 4 次方）
- 每个子网可用主机
- 4,094
- 块大小
- 16
算法
从 /16 到 /20，网络位多了 4 位，所以子网数是 2 的 4 次方，等于 16。主机位剩 12 位，每个子网 4,096 个地址，去掉网络地址和广播地址，剩 4,094 台。表里相邻两行的网络地址正好差一个块大小 16。
| # | 网络地址 | 首个可用 | 末个可用 | 广播地址 | 可用主机数 |
|---|---|---|---|---|---|
| 1 | 172.16.0.0/20 | 172.16.0.1 | 172.16.15.254 | 172.16.15.255 | 4,094 |
| 2 | 172.16.16.0/20 | 172.16.16.1 | 172.16.31.254 | 172.16.31.255 | 4,094 |
| 3 | 172.16.32.0/20 | 172.16.32.1 | 172.16.47.254 | 172.16.47.255 | 4,094 |
| 4 | 172.16.48.0/20 | 172.16.48.1 | 172.16.63.254 | 172.16.63.255 | 4,094 |
| 5 | 172.16.64.0/20 | 172.16.64.1 | 172.16.79.254 | 172.16.79.255 | 4,094 |
| 6 | 172.16.80.0/20 | 172.16.80.1 | 172.16.95.254 | 172.16.95.255 | 4,094 |
| 7 | 172.16.96.0/20 | 172.16.96.1 | 172.16.111.254 | 172.16.111.255 | 4,094 |
| 8 | 172.16.112.0/20 | 172.16.112.1 | 172.16.127.254 | 172.16.127.255 | 4,094 |
| 9 | 172.16.128.0/20 | 172.16.128.1 | 172.16.143.254 | 172.16.143.255 | 4,094 |
| 10 | 172.16.144.0/20 | 172.16.144.1 | 172.16.159.254 | 172.16.159.255 | 4,094 |
| 11 | 172.16.160.0/20 | 172.16.160.1 | 172.16.175.254 | 172.16.175.255 | 4,094 |
| 12 | 172.16.176.0/20 | 172.16.176.1 | 172.16.191.254 | 172.16.191.255 | 4,094 |
| 13 | 172.16.192.0/20 | 172.16.192.1 | 172.16.207.254 | 172.16.207.255 | 4,094 |
| 14 | 172.16.208.0/20 | 172.16.208.1 | 172.16.223.254 | 172.16.223.255 | 4,094 |
| 15 | 172.16.224.0/20 | 172.16.224.1 | 172.16.239.254 | 172.16.239.255 | 4,094 |
| 16 | 172.16.240.0/20 | 172.16.240.1 | 172.16.255.254 | 172.16.255.255 | 4,094 |