IPv4

IPv4 is the 32-bit network addressing protocol, written in dotted decimal (e.g., 192.168.1.1), with roughly 4.3 billion addresses—now exhausted.

Purpose

It provides the Internet's addressing scheme and is being replaced by IPv6 as its address space runs out.

Mechanism

The 32 bits appear as four 8-bit decimal octets. Address classes (A/B/C/D/E) were superseded by CIDR. Private addresses (RFC 1918) reach the public Internet through NAT. Special addresses include 0.0.0.0 (any), 127.0.0.0/8 (loopback), and 255.255.255.255 (broadcast).

Use cases

LAN addressing
NAT and port forwarding
Legacy system compatibility
Networking education

Examples

Input
```
10.0.0.1
```
Output
```
A private class A address
```
RFC 1918

Common errors

Public IPv4 is exhausted; new deployments cannot obtain addresses: Migrate to IPv6 or use NAT

Related terms

An IP address is the numeric identifier assigned to a network interface—32 bits for IPv4 (four decimal octets) and 128 bits for IPv6 (eight hexadecimal groups)—used for network addressing.

IPv6 is the 128-bit network addressing protocol, written in colon-separated hexadecimal (e.g., 2001:db8::1), offering about 3.4×10^38 addresses to solve IPv4 exhaustion.

A subnet is a technique for dividing a large network into smaller ones, using the subnet mask to separate the network number from the host number, improving address utilization and isolation.

CIDR (Classless Inter-Domain Routing) expresses a network as IP/prefix length (e.g., 10.0.0.0/8), replacing IPv4 address classes with flexible network partitioning.

Related tools

IP Address Info

Analyze IPv4/IPv6 addresses and CIDR subnets: class, private/multicast flags, binary/hex, reverse DNS, network/broadcast/hosts. Free, private, and 100% client-side.

References