IPv4

IPv4 (Internet Protocol version 4) is the fourth version of the Internet Protocol, providing addressing and routing of data across networks. Introduced in 1981, it still forms the foundation of the Internet despite the gradual transition to IPv6.

IPv4 uses 32-bit addresses, which allow for about 4.3 billion unique combinations. The format is four decimal numbers (0–255) separated by dots (e.g., 192.168.0.1).

Key Features of IPv4

• Simple addressing structure – human-readable dotted-decimal format.
• NAT support – allows multiple devices to share a single public address.
• Public and private address ranges – separation for internal and external use.
• Subnet masks – divide networks into segments.
• Broad compatibility – supported by all networking devices and software.

IPv4 Address Structure

An IP address consists of two parts:

• Network portion – identifies the specific network.
• Host portion – identifies the device within that network.

For example, in the address 192.168.1.15 with subnet mask 255.255.255.0, the network is 192.168.1 and the host is 15.

Issues and Limitations

• Limited address space – about 4.3 billion, which became insufficient as the Internet grew.
• Reliance on NAT and CG-NAT – providers must use address translation due to scarcity.
• Lack of built-in security – no native encryption mechanisms.
• Uneven distribution – some address blocks are allocated but not efficiently used.

Applications

Despite IPv6 adoption, IPv4 remains the dominant protocol:

• used in most home and corporate networks;
• forms the backbone of the Internet;
• supported by ISPs, data centers, routers, and servers.

Example

A home router receives a public IPv4 address 95.24.123.15 from the ISP. Inside the local network, it assigns private IPv4 addresses (e.g., 192.168.0.2, 192.168.0.3) to laptops and phones, using NAT for Internet access.

Frequently Asked Questions (FAQ)

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