
IPV4 or Internet Protocol Version 4 is an address that provides a unique identity to the devices on the Internet and Intranet. For Example (Non-Technical) Two people from different countries want to talk to each other with their mobile phones but if they don’t own a phone number, they can’t be able to contact each other likewise If we want to communicate on the Internet or Intranet, we need a special address (192.168.1.1).
IPV4 address is 32 bits and is divided into four equal parts/octets. Each part has 8 bits. So, each octet has a range of 0-255(2^8=256) as here we are counting from 0 that’s why we are taking it to 255.
Now IP is further divided into two parts-
- Public IP Address
- Private IP Address

Classes of IPV4
IPV4 is divided into further 5 Classes and each class has its use and property
- Class A (0-127)
- Class B (128-191)
- Class C (192-223)
- Class D (224-239)
- Class E (240-255)
Now, one question strikes our mind: How will we know that this IP address is of which class? The Answer is by seeing their First octet/part if the number lies in between the range it belongs to that class
For Ex- 10.165.192.239 by looking at this IP address the highlighted number 10 is in the first part/octet. Now we must check from the range that 10 lies in which class. The answer is Class A i.e. (0-127).
Class A
- This Class range lies from 0-127.
- This Class is used when we are using default routing (0.0.0.0/0)
- This Class is also used for LAN Card testing (127.0.0.0 to 127.255.255.255)
- This Class is also used in DHCP Packets.
- The private IP range is from 10.0.0.0 to 10.255.255.255(Note- locally we use a private IP address but for internet access, we need a public IP address)
- Except that all IPs are for Public IP addresses.
Class B
- This Class range lies from 128-191.
- This Class is used for APIPA (Automatic Private IP Addressing) in DHCP (169.254.0.1 to 169.254.255.254)
- The private IP range is from 172.16.0.0 to 172.31.255.255.
- Except that all IP addresses are Public IP addresses.
Class C
- This Class range lies from 192-223.
- This Class has no reserved IP address.
- The private IP range is from 192.168.0.0 to 192.168.255.25.
- Mostly we use this class of IP address for Communication.
- Except that all IP addresses are Public IP addresses.
Class D
- This Class range lies from 224-239.
- This Class is not used for assigning IP addresses to the devices.
- This Class is specially designed for Multicasting purposes.
Class E
- This Class range lies from 240-255.
- This whole class is reserved for Scientific purposes and R & D.
Nowadays we are also using the enhanced version of IPV4 which is IPV6.
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Author
Abhishek Kaushik
Associate Consultant