www.m9-com.ru

https://www.nic.ru/ip-reg/info/pref.txt


+----------------------------------------------+
|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 |
+----------------------------------------------+