切分表
10.0.0.0/8 切成 /12
借 4 位，16 个子网，每个 1,048,574 台可用主机。
- 原网段
- 10.0.0.0/8
- 新掩码
- 255.240.0.0
- 子网个数
- 16（2 的 4 次方）
- 每个子网可用主机
- 1,048,574
- 块大小
- 16
算法
从 /8 到 /12，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 20 位，每个子网 1,048,576 个地址，去掉网络地址和广播地址，剩 1,048,574 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 | 10.0.0.0/12 | 10.0.0.1 | 10.15.255.254 | 10.15.255.255 | 1,048,574 |
| 2 | 10.16.0.0/12 | 10.16.0.1 | 10.31.255.254 | 10.31.255.255 | 1,048,574 |
| 3 | 10.32.0.0/12 | 10.32.0.1 | 10.47.255.254 | 10.47.255.255 | 1,048,574 |
| 4 | 10.48.0.0/12 | 10.48.0.1 | 10.63.255.254 | 10.63.255.255 | 1,048,574 |
| 5 | 10.64.0.0/12 | 10.64.0.1 | 10.79.255.254 | 10.79.255.255 | 1,048,574 |
| 6 | 10.80.0.0/12 | 10.80.0.1 | 10.95.255.254 | 10.95.255.255 | 1,048,574 |
| 7 | 10.96.0.0/12 | 10.96.0.1 | 10.111.255.254 | 10.111.255.255 | 1,048,574 |
| 8 | 10.112.0.0/12 | 10.112.0.1 | 10.127.255.254 | 10.127.255.255 | 1,048,574 |
| 9 | 10.128.0.0/12 | 10.128.0.1 | 10.143.255.254 | 10.143.255.255 | 1,048,574 |
| 10 | 10.144.0.0/12 | 10.144.0.1 | 10.159.255.254 | 10.159.255.255 | 1,048,574 |
| 11 | 10.160.0.0/12 | 10.160.0.1 | 10.175.255.254 | 10.175.255.255 | 1,048,574 |
| 12 | 10.176.0.0/12 | 10.176.0.1 | 10.191.255.254 | 10.191.255.255 | 1,048,574 |
| 13 | 10.192.0.0/12 | 10.192.0.1 | 10.207.255.254 | 10.207.255.255 | 1,048,574 |
| 14 | 10.208.0.0/12 | 10.208.0.1 | 10.223.255.254 | 10.223.255.255 | 1,048,574 |
| 15 | 10.224.0.0/12 | 10.224.0.1 | 10.239.255.254 | 10.239.255.255 | 1,048,574 |
| 16 | 10.240.0.0/12 | 10.240.0.1 | 10.255.255.254 | 10.255.255.255 | 1,048,574 |