切分表
10.0.0.0/16 切成 /21
借 5 位，32 个子网，每个 2,046 台可用主机。
- 原网段
- 10.0.0.0/16
- 新掩码
- 255.255.248.0
- 子网个数
- 32（2 的 5 次方）
- 每个子网可用主机
- 2,046
- 块大小
- 8
算法
从 /16 到 /21，网络位多了 5 位，所以子网数是 2 的 5 次方，等于 32。主机位剩 11 位，每个子网 2,048 个地址，去掉网络地址和广播地址，剩 2,046 台。表里相邻两行的网络地址正好差一个块大小 8。
| # | 网络地址 | 首个可用 | 末个可用 | 广播地址 | 可用主机数 |
|---|---|---|---|---|---|
| 1 | 10.0.0.0/21 | 10.0.0.1 | 10.0.7.254 | 10.0.7.255 | 2,046 |
| 2 | 10.0.8.0/21 | 10.0.8.1 | 10.0.15.254 | 10.0.15.255 | 2,046 |
| 3 | 10.0.16.0/21 | 10.0.16.1 | 10.0.23.254 | 10.0.23.255 | 2,046 |
| 4 | 10.0.24.0/21 | 10.0.24.1 | 10.0.31.254 | 10.0.31.255 | 2,046 |
| 5 | 10.0.32.0/21 | 10.0.32.1 | 10.0.39.254 | 10.0.39.255 | 2,046 |
| 6 | 10.0.40.0/21 | 10.0.40.1 | 10.0.47.254 | 10.0.47.255 | 2,046 |
| 7 | 10.0.48.0/21 | 10.0.48.1 | 10.0.55.254 | 10.0.55.255 | 2,046 |
| 8 | 10.0.56.0/21 | 10.0.56.1 | 10.0.63.254 | 10.0.63.255 | 2,046 |
| 9 | 10.0.64.0/21 | 10.0.64.1 | 10.0.71.254 | 10.0.71.255 | 2,046 |
| 10 | 10.0.72.0/21 | 10.0.72.1 | 10.0.79.254 | 10.0.79.255 | 2,046 |
| 11 | 10.0.80.0/21 | 10.0.80.1 | 10.0.87.254 | 10.0.87.255 | 2,046 |
| 12 | 10.0.88.0/21 | 10.0.88.1 | 10.0.95.254 | 10.0.95.255 | 2,046 |
| 13 | 10.0.96.0/21 | 10.0.96.1 | 10.0.103.254 | 10.0.103.255 | 2,046 |
| 14 | 10.0.104.0/21 | 10.0.104.1 | 10.0.111.254 | 10.0.111.255 | 2,046 |
| 15 | 10.0.112.0/21 | 10.0.112.1 | 10.0.119.254 | 10.0.119.255 | 2,046 |
| 16 | 10.0.120.0/21 | 10.0.120.1 | 10.0.127.254 | 10.0.127.255 | 2,046 |
| 17 | 10.0.128.0/21 | 10.0.128.1 | 10.0.135.254 | 10.0.135.255 | 2,046 |
| 18 | 10.0.136.0/21 | 10.0.136.1 | 10.0.143.254 | 10.0.143.255 | 2,046 |
| 19 | 10.0.144.0/21 | 10.0.144.1 | 10.0.151.254 | 10.0.151.255 | 2,046 |
| 20 | 10.0.152.0/21 | 10.0.152.1 | 10.0.159.254 | 10.0.159.255 | 2,046 |
| 21 | 10.0.160.0/21 | 10.0.160.1 | 10.0.167.254 | 10.0.167.255 | 2,046 |
| 22 | 10.0.168.0/21 | 10.0.168.1 | 10.0.175.254 | 10.0.175.255 | 2,046 |
| 23 | 10.0.176.0/21 | 10.0.176.1 | 10.0.183.254 | 10.0.183.255 | 2,046 |
| 24 | 10.0.184.0/21 | 10.0.184.1 | 10.0.191.254 | 10.0.191.255 | 2,046 |
| 25 | 10.0.192.0/21 | 10.0.192.1 | 10.0.199.254 | 10.0.199.255 | 2,046 |
| 26 | 10.0.200.0/21 | 10.0.200.1 | 10.0.207.254 | 10.0.207.255 | 2,046 |
| 27 | 10.0.208.0/21 | 10.0.208.1 | 10.0.215.254 | 10.0.215.255 | 2,046 |
| 28 | 10.0.216.0/21 | 10.0.216.1 | 10.0.223.254 | 10.0.223.255 | 2,046 |
| 29 | 10.0.224.0/21 | 10.0.224.1 | 10.0.231.254 | 10.0.231.255 | 2,046 |
| 30 | 10.0.232.0/21 | 10.0.232.1 | 10.0.239.254 | 10.0.239.255 | 2,046 |
| 31 | 10.0.240.0/21 | 10.0.240.1 | 10.0.247.254 | 10.0.247.255 | 2,046 |
| 32 | 10.0.248.0/21 | 10.0.248.1 | 10.0.255.254 | 10.0.255.255 | 2,046 |