What is Internet Protocol Version 4 (IPv4)?
A way to identity machine on the network, Protocols are set of rules for regulating communication between machines. And TCP/IP is the de-facto communication standard used by internet. It was originally developed by the US Department of Defense (DOD) in the 1970‘s to provide a robust network that could support military network in the event of nuclear war and it also known as Identifier man network. TCP lies between the application n network layers and server as the intermediary between the applications and the network operations. A comprehensive technical breakdown of IPv4 address structure, binary octet allocations, governing bodies (IANA & ICANN), and classful subnet dynamics.
32-Bit Structure and Octet Decimal Notation
An IPv4 address consists of 32 binary bits broken down into four 8-bit sections known as octets. In dotted-decimal notation, each octet takes a decimal value between 0 and 255.
Static vs. Dynamic IP Address Allocation
| IP Assignment Type | Configuration Method | Primary Use Cases |
|---|---|---|
| Static IP Address | Configured manually by network administrators. | Servers, DNS gateways, VPN servers and enterprise hardware. |
| Dynamic IP Address | Leased automatically via Dynamic Host Configuration Protocol (DHCP). | Client endpoints, mobile devices, laptops and home Wi-Fi networks. |
Global IP Allocation Bodies: IANA vs. ICANN
| Organization | Full Name | Primary Responsibilities |
|---|---|---|
| IANA | Internet Assigned Numbers Authority | Oversees global IP allocation, Autonomous System Numbers (ASN), and DNS root zone management. |
| ICANN | Internet Corporation for Assigned Names and Numbers | Private non-profit entity that maintains root system stability and manages IANA operations. |
1.1 # Classful IPv4 Address Specifications
Traditional IPv4 networking categorizes addresses into five distinct classes (Class A through E) based on leading binary bit patterns. However, we should first understand Truth Tables before setting up IPv4.
| Class | Leading Bits | 1st Octet Range | Net / Host Split | Total Networks | Usable Hosts per Network |
|---|---|---|---|---|---|
| Class A | 0 | 1 – 126 | 8 bits / 24 bits | 128 (27) | 16,777,216 (224) |
It is the part of internet protocol hierarchical addressing scheme is that reserved for governments. It works have only 8 bits for defining network (First octets can’t be changed in network ID) and 24 bits for defining host and subnets on each networks.
The Class A originally start from 0.0.0.0 — 127.255.255.255 for the being generally, we speak begins to 1 and end with 126 (1-126).
Note : -
Reserved strictly for internal loopback testing 127.0.0.0 /8 (127.0.0.0 – 127.255.255.255). Traffic sent to this block never leaves the local machine.
Let's walk through the proof
Address notation : 0nnnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh
Binary notation : 00000000.00000000.00000000.00000000 = 0.0.0.0
===========> 01111111.11111111.11111111.11111111 = 127.255.255.255
| Class | Leading Bits | 1st Octet Range | Net / Host Split | Total Networks | Usable Hosts per Network |
|---|---|---|---|---|---|
| Class B | 10 | 128 – 191 | 16 bits / 16 bits | 16,384 (214) | 65,536 (216) |
It is the part of internet protocol hierarchical addressing scheme is that reserved for medium companies. It works have 16 bits for defining network and 16 bits for defining host and subnets on each networks.
The Class B originally start from 128.0.0.0 — 191.255.255.255
Note : -
"169.254.0.0/16 is reserved for APIPA (Automatic Private IP Addressing), assigned automatically by the host when a DHCP server is unreachable."
Let's walk through the proof
Address notation : 10nnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh
Binary notation : 10000000.00000000.00000000.00000000 = 128.0.0.0
===========> 10111111.11111111.11111111.11111111 = 191.255.255.255
| Class | Leading Bits | 1st Octet Range | Net / Host Split | Total Networks | Usable Hosts per Network |
|---|---|---|---|---|---|
| Class C | 110 | 192 – 223 | 24 bits / 8 bits | 2,097,152 (221) | 256 (28) |
It the part of internet protocol hierarchical addressing scheme is that reserved for small companies. It works have 24 bits for defining network and only 8 bits for defining host and subnets on each networks. Generally it begins 192 to 223. The Class C originally start from 192.0.0.0 — 223.255.255.255
Note : -
1. Private Networking (RFC 1918)192.168.0.0 – 192.168.255.255 (192.168.0.0/16)
Reserved exclusively for private Local Area Networks (LANs), like home routers and internal business networks. Traffic to this block is non-routable over the public internet.
2. Documentation & Testing (RFC 5737 - TEST-NETs)
192.0.2.0/24 (192.0.2.0 – 192.0.2.255) — TEST-NET-1
198.51.100.0/24 (198.51.100.0 – 198.51.100.255) — TEST-NET-2
203.0.113.0/24 (203.0.113.0 – 203.0.113.255) — TEST-NET-3
Reserved specifically for use in network textbooks, technical documentation, and code examples to prevent accidental routing conflicts.
3. Protocol Extensions & Relay Special Ranges
192.0.0.0/24 (RFC 6890) — Reserved for IETF Protocol Assignments (e.g., Dual-Stack Lite).
192.88.99.0/24 (RFC 7526) — Formerly reserved for 6to4 Anycast relay mechanisms (now deprecated to unicast).
Let's walk through the proof
Address notation : 110nnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh
Binary notation : 11000000.00000000.00000000.00000000 = 192.0.0.0
===========> 11011111.11111111.11111111.11111111 = 223.255.255.255
| Class | Leading Bits | 1st Octet Range | Net / Host Split | Total Networks | Usable Hosts per Network |
|---|---|---|---|---|---|
| Class D | 1110 | 224 – 239 | Multicast Group | N/A | 268,435,456 Groups |
It is the part of internet protocol hierarchical addressing scheme is that reserved for multicasting groups (one-two many communications). They do not have network and host parts like Classes A, B, or C. 4 bits are used to define the class (network identification) and 28 bits are used to define the multicast group (2²8 = 268,435,456) there are no host bits. for example, video streaming, conferencing, or online gaming. The Class D originally start from 224.0.0.0 — 239.255.255.255
Note : -
They are not assigned to individual devices but to multicast groups. Generally it begins 224 to 239.
Let's walk through the proof
Address notation : 1110mmmm.mmmmmmmm.mmmmmmmm.mmmmmmmm
Binary notation : 11100000.00000000.00000000.00000000 = 224.0.0.0
===========> 11101111.11111111.11111111.11111111 = 239.255.255.255
| Class | Leading Bits | 1st Octet Range | Net / Host Split | Total Networks | Usable Hosts per Network |
|---|---|---|---|---|---|
| Class E | 1111 | 240 – 255 | Experimental | N/A | Reserved for Research |
It is the part of the IPv4 hierarchical addressing scheme reserved for future research, dynamic testing, or experimental purposes. Addresses in Class E are not assigned to end-host interfaces or routed across public networks. for example, Cloud Network Expansion (Internal Private VPCs), Isolated Lab Testing & Protocol Experiments, Cybersecurity Honeypots & Threat Analysis and Limited Broadcast. The Class E originally start from 240.0.0.0 — 255.255.255.255
Note : -
In large cloud platforms like Google Cloud Platform (GCP) or AWS, massive Kubernetes clusters run out of private IPv4 addresses (RFC 1918 ranges like 10.0.0.0/8 or 192.168.0.0/16). Cloud providers use Class E blocks internally to expand IP capacity without causing conflicts.
Example IP: 240.10.20.15
Usage: Assigned as an internal Pod address inside a Google Kubernetes Engine (GKE) cluster.
How it works: A service inside the cloud uses 240.10.20.15 internally. When communicating outside the cloud, a NAT gateway translates it back into a standard public or private IP.
Let's walk through the proof
Address notation : 1111xxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx
Binary notation : 11110000.00000000.00000000.00000000 = 240.0.0.0
===========> 11111111.11111111.11111111.11111111 = 255.255.255.255
Frequently Asked Questions (FAQ)
An IPv4 address is 32 bits long, divided into 4 octets (8 bits per section) written in dotted-decimal format ranging from 0.0.0.0 to 255.255.255.255.
Static IP addresses are manually assigned to host devices and remain fixed, whereas Dynamic IP addresses are automatically leased to hosts via DHCP and change periodically.
Class A covers 1.0.0.0 to 126.255.255.255, Class B covers 128.0.0.0 to 191.255.255.255, and Class C covers 192.0.0.0 to 223.255.255.255.
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