IPv4 Classes : uses – subnet mask – Possible No of Hosts
| IP Class | Range | Use | Subnet | Subnet indication | Usable IP’s |
| Class A | 0-126 | Large No of Hosts | 255.0.0.0 | N.H.H.H | 16 Million |
| Class B | 129-191 | Medium Size N/W | 255.255.0.0 | N.N.H.H | 65 Thousand |
| Class C | 192-223 | Local Area N/W | 255.255.255.0 | N.N.N.H | 256 |
| Class D | 224-239 | Reserved for Multicasting | – | – | – |
| Class E | 240-255 | Research and Development , Future Use | – | – | – |
127 is loopback IP used for testing purpose - local host