IPv4 subnetting


+----------------------------------------------+
|addrs   bits   pref   class*  mask            |
+----------------------------------------------+
|    1      0    /32           255.255.255.255 |
|    2      1    /31           255.255.255.254 |
|    4      2    /30           255.255.255.252 |
|    8      3    /29           255.255.255.248 |
|   16      4    /28           255.255.255.240 |
|   32      5    /27           255.255.255.224 |
|   64      6    /26           255.255.255.192 |
|  128      7    /25           255.255.255.128 |
|  256      8    /24      1C   255.255.255     |
|  512      9    /23      2C   255.255.254     |
|   1K     10    /22      4C   255.255.252     |
|   2K     11    /21      8C   255.255.248     |
|   4K     12    /20     16C   255.255.240     |
|   8K     13    /19     32C   255.255.224     |
|  16K     14    /18     64C   255.255.192     |
|  32K     15    /17    128C   255.255.128     |
|  64K     16    /16      1B   255.255         |
| 128K     17    /15      2B   255.254         |
| 256K     18    /14      4B   255.252         |
| 512K     19    /13      8B   255.248         |
|   1M     20    /12     16B   255.240         |
|   2M     21    /11     32B   255.224         |
|   4M     22    /10     64B   255.192         |
|   8M     23     /9    128B   255.128         |
|  16M     24     /8      1A   255             |
|  32M     25     /7      2A   254             |
|  64M     26     /6      4A   252             |
| 128M     27     /5      8A   248             |
| 256M     28     /4     16A   240             |
| 512M     29     /3     32A   224             |
|1024M     30     /2     64A   192             |
+----------------------------------------------+

The Internet Assigned Numbers Authority (IANA) has reserved the 
following three blocks of the IP address space for private internets:

     10.0.0.0        -   10.255.255.255  (10/8 prefix)
     172.16.0.0      -   172.31.255.255  (172.16/12 prefix)
     192.168.0.0     -   192.168.255.255 (192.168/16 prefix)
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