+-------+------+------+-------+-----------------+
| 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             |
| 2048M |  31  |   /1 |  128A | 128             |
+-------+------+------+-------+-----------------+