Classes
| Class | Start address | Finish address |
|---|
| A | 0.0.0.0 | 126.255.255.255 |
| B | 128.0.0.0 | 191.255.255.255 |
| C | 192.0.0.0 | 223.255.255.255 |
| D | 224.0.0.0 | 239.255.255.255 |
| E | 240.0.0.0 | 255.255.255.255 |
Address ranges to be use by private networks are:
| Class | Start address | Finish address |
|---|
| A | 10.0.0.0 | 10.255.255.255 |
| B | 172.16.0.0 | 172.31.255.255 |
| C | 192.168.0.0 | 192.168.255.255 |
Subnets and Masks
| Class | Address | # of Hosts | Netmask (Decimal) |
|---|
| CIDR | /4 | 240,435,456 | 240.0.0.0 |
| CIDR | /5 | 134,217,728 | 248.0.0.0 |
| CIDR | /6 | 67,108,864 | 252.0.0.0 |
| CIDR | /7 | 33,554,432 | 254.0.0.0 |
| A | /8 | 16,777,216 | 255.0.0.0 |
| CIDR | /9 | 8,388,608 | 255.128.0.0 |
| CIDR | /10 | 4,194,304 | 255.192.0.0 |
| CIDR | /11 | 2,097,152 | 255.224.0.0 |
| CIDR | /12 | 1,048,576 | 255.240.0.0 |
| CIDR | /13 | 524,288 | 255.248.0.0 |
| CIDR | /14 | 262,144 | 255.252.0.0 |
| CIDR | /15 | 131,072 | 255.254.0.0 |
| B | /16 | 65,534 | 255.255.0.0 |
| CIDR | /17 | 32,768 | 255.255.128.0 |
| CIDR | /18 | 16,384 | 255.255.192.0 |
| CIDR | /19 | 8,192 | 255.255.224.0 |
| CIDR | /20 | 4,096 | 255.255.240.0 |
| CIDR | /21 | 2,048 | 255.255.248.0 |
| CIDR | /22 | 1,024 | 255.255.252.0 |
| CIDR | /23 | 512 | 255.255.254.0 |
| C | /24 | 256 | 255.255.255.0 |
| CIDR | /25 | 128 | 255.255.255.128 |
| CIDR | /26 | 64 | 255.255.255.192 |
| CIDR | /27 | 32 | 255.255.255.224 |
| CIDR | /28 | 16 | 255.255.255.240 |
| CIDR | /29 | 8 | 255.255.255.248 |
| CIDR | /30 | 4 | 255.255.255.252 |