| Class | 1st Octet Decimal Range | 1st Octet High Order Bits | Network/Host ID (N=Network, H=Host) | Default Subnet Mask | Number of Networks | Hosts per Network (Usable Addresses) |
|---|---|---|---|---|---|---|
| A | 1 – 126* | 0 | N.H.H.H | 255.0.0.0 | 126 (27 – 2) | 16,777,214 (224 – 2) |
| B | 128 – 191 | 10 | N.N.H.H | 255.255.0.0 | 16,382 (214 – 2) | 65,534 (216 – 2) |
| C | 192 – 223 | 110 | N.N.N.H | 255.255.255.0 | 2,097,150 (221 – 2) | 254 (28 – 2) |
| D | 224 – 239 | 1110 | Reserved for Multicasting | |||
| E | 240 – 254 | 1111 | Experimental; used for research | |||
Note: Class A addresses 127.0.0.0 to 127.255.255.255 cannot be used and is reserved for loopback and diagnostic functions.
Private IP Addresses
| Class | Private Networks | Subnet Mask | Address Range |
|---|---|---|---|
| A | 10.0.0.0 | 255.0.0.0 | 10.0.0.0 - 10.255.255.255 |
| B | 172.16.0.0 - 172.31.0.0 | 255.240.0.0 | 172.16.0.0 - 172.31.255.255 |
| C | 192.168.0.0 | 255.255.0.0 | 192.168.0.0 - 192.168.255.255 |
Subnet Masks
| Prefix Format | Decimal | Available Host Addresses |
|---|---|---|
| /8 | 255.0.0.0 | 16777214 |
| /9 | 255.128.0.0 | 8388606 |
| /10 | 255.192.0.0 | 4194302 |
| /11 | 255.224.0.0 | 2097150 |
| /12 | 255.240.0.0 | 1048574 |
| /13 | 255.248.0.0 | 524286 |
| /14 | 255.252.0.0 | 262142 |
| /15 | 255.254.0.0 | 131070 |
| /16 | 255.255.0.0 | 65534 |
| /17 | 255.255.128.0 | 32766 |
| /18 | 255.255.192.0 | 16382 |
| /19 | 255.255.224.0 | 8190 |
| /20 | 255.255.240.0 | 4094 |
| /21 | 255.255.248.0 | 2046 |
| /22 | 255.255.252.0 | 1022 |
| /23 | 255.255.254.0 | 510 |
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /30 | 255.255.255.252 | 2 |
