| 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 | 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 |
Note:
There is another range of IP addresses reserved for private networks:-
| Type | Private Networks | Subnet Mask | Address Range |
|---|---|---|---|
| APIPA | 169.254.0.0 | 255.255.0.0 | 169.254.0.0 – 169.254.255.255 |
| Test | 198.18.0.0 | 255.254.00.0 | 198.18.0.0 – 198.19.255.255 |
APIPA range (Ah-peep-ah) – Automatic Private IP Addressing.
Microsoft has incorporated this into all versions of Windows.
The APIPA system gives nothing but trouble!
Microsoft has incorporated this into all versions of Windows.
The APIPA system gives nothing but trouble!