ip地址位数表
掩码 | 位数 | 可用主机数（主机地址数） |
|---|---|---|
255.0.0.0 | 8 | 16777216-2=16777214 |
255.128.0.0 | 9 | 8388608-2=8388606 |
255.192.0.0 | 10 | 4194304-2=4194302 |
255.224.0.0 | 11 | 2097152-2=2097150 |
255.240.0.0 | 12 | 1048576-2=1048574 |
255.248.0.0 | 13 | 524288-2=524286 |
255.252.0.0 | 14 | 262143=262142 |
255.254.0.0 | 15 | 131072-2=131070 |
255.255.0.0 | 16 | 65536-2=65534 |
255.255.128.0 | 17 | 32768-2=32766 |
255.255.192.0 | 18 | 16384-2=16382 |
255.255.224.0 | 19 | 8192-2=8190 |
255.255.240.0 | 20 | 4096-2=4094 |
255.255.248.0 | 21 | 2048-2=2046 |
255.255.252.0 | 22 | 1024-2=1022 |
255.255.254.0 | 23 | 511=510 |
255.255.255.0 | 24 | 256-2=254 |
255.255.255.128 | 25 | 128-2=126 |
255.255.255.192 | 26 | 64-2=62 |
255.255.255.224 | 27 | 31=30 |
255.255.255.240 | 28 | 16-2=14 |
255.255.255.248 | 29 | 8-2=6 |
255.255.255.252 | 30 | 4-2=2 |
