What is IPv4?
IPv4 (Internet Protocol version 4) is the fourth version of the Internet Protocol and the most widely deployed protocol for routing internet traffic. It uses 32-bit addresses written in dotted-decimal notation (e.g., 192.168.1.1) and provides the foundation for modern internet communication.
IPv4 Address Structure
Address Format
192.168.1.100
Binary representation:
11000000.10101000.00000001.01100100
32 bits total = 4 bytes (octets)
Each octet: 0-255
Total addresses: 2^32 = 4,294,967,296
Address Classes
// Class A: 1.0.0.0 to 126.255.255.255
// Network bits: 8, Host bits: 24
// Used for: Large networks (16.7M hosts)
// Class B: 128.0.0.0 to 191.255.255.255
// Network bits: 16, Host bits: 16
// Used for: Medium networks (65,536 hosts)
// Class C: 192.0.0.0 to 223.255.255.255
// Network bits: 24, Host bits: 8
// Used for: Small networks (254 hosts)
// Class D: 224.0.0.0 to 239.255.255.255
// Used for: Multicast
// Class E: 240.0.0.0 to 255.255.255.255
// Reserved for experimental usePrivate IPv4 Ranges
Reserved Address Spaces
interface PrivateRanges {
classA: '10.0.0.0/8'; // 10.0.0.0 - 10.255.255.255
classB: '172.16.0.0/12'; // 172.16.0.0 - 172.31.255.255
classC: '192.168.0.0/16'; // 192.168.0.0 - 192.168.255.255
loopback: '127.0.0.0/8'; // 127.0.0.1 (localhost)
linkLocal: '169.254.0.0/16'; // Auto-configuration
}
// Example: Check if IP is private
function isPrivateIPv4(ip: string): boolean {
const parts = ip.split('.').map(Number);
const firstOctet = parts[0];
const secondOctet = parts[1];
// Class A private
if (firstOctet === 10) return true;
// Class B private
if (firstOctet === 172 && secondOctet >= 16 && secondOctet <= 31) return true;
// Class C private
if (firstOctet === 192 && secondOctet === 168) return true;
// Loopback
if (firstOctet === 127) return true;
return false;
}IPv4 with Proxy Servers
Specifying IPv4 in Requests
// Using CorsProxy with IPv4
const response = await fetch(
'https://corsproxy.io/?url=https://api.example.com/data',
{
headers: {
'x-cors-api-key': process.env.CORS_API_KEY,
'x-cors-proxy-type': 'datacenter',
// Proxy will use IPv4 by default
}
}
);
// Getting your current IPv4 address
const ipResponse = await fetch('https://api.ipify.org?format=json');
const { ip } = await ipResponse.json();
console.log(`Your IPv4: ${ip}`);IPv4 Proxy Configuration
class IPv4ProxyManager {
private proxyList: string[];
constructor(proxies: string[]) {
this.proxyList = proxies;
}
// Rotate through IPv4 proxies
getNextProxy(): string {
const proxy = this.proxyList.shift();
if (proxy) {
this.proxyList.push(proxy);
return proxy;
}
throw new Error('No proxies available');
}
// Validate IPv4 format
isValidIPv4(ip: string): boolean {
const parts = ip.split('.');
if (parts.length !== 4) return false;
return parts.every(part => {
const num = parseInt(part, 10);
return num >= 0 && num <= 255 && part === num.toString();
});
}
}
// Usage
const manager = new IPv4ProxyManager([
'203.0.113.1:8080',
'203.0.113.2:8080',
'203.0.113.3:8080'
]);
const proxy = manager.getNextProxy();CIDR Notation
Subnet Masks
// CIDR (Classless Inter-Domain Routing)
// Format: IP/prefix-length
interface CIDRBlock {
notation: '192.168.1.0/24';
netmask: '255.255.255.0';
network: '192.168.1.0';
broadcast: '192.168.1.255';
usableIPs: 254; // .1 to .254
totalIPs: 256;
}
// Calculate network range
function calculateCIDR(cidr: string) {
const [ip, prefixStr] = cidr.split('/');
const prefix = parseInt(prefixStr, 10);
const totalIPs = Math.pow(2, 32 - prefix);
const usableIPs = totalIPs - 2; // Subtract network and broadcast
return {
ip,
prefix,
totalIPs,
usableIPs,
subnetMask: calculateSubnetMask(prefix)
};
}
function calculateSubnetMask(prefix: number): string {
const mask = ~((1 << (32 - prefix)) - 1);
return [
(mask >>> 24) & 255,
(mask >>> 16) & 255,
(mask >>> 8) & 255,
mask & 255
].join('.');
}
// Examples
console.log(calculateCIDR('10.0.0.0/8')); // 16,777,216 IPs
console.log(calculateCIDR('172.16.0.0/12')); // 1,048,576 IPs
console.log(calculateCIDR('192.168.1.0/24')); // 256 IPsIPv4 Exhaustion
The Address Shortage
Total IPv4 addresses: 4,294,967,296
Reserved/Private: ~600 million
Publicly routable: ~3.7 billion
World population: 8+ billion
Internet users: 5+ billion
Connected devices: 50+ billion
Solution: IPv6 (340 undecillion addresses)
NAT (Network Address Translation)
// NAT allows multiple devices to share one public IPv4
/*
Public IPv4: 203.0.113.50
Private Network:
├─ 192.168.1.10 (Device 1)
├─ 192.168.1.11 (Device 2)
└─ 192.168.1.12 (Device 3)
All devices share 203.0.113.50 for outbound connections
*/
// Detecting NAT
async function detectNAT() {
// Get public IP
const publicResponse = await fetch('https://api.ipify.org?format=json');
const { ip: publicIP } = await publicResponse.json();
// Get local IP (browser example)
const pc = new RTCPeerConnection({ iceServers: [] });
pc.createDataChannel('');
const offer = await pc.createOffer();
await pc.setLocalDescription(offer);
const localIP = offer.sdp.split('\n')
.find(line => line.includes('candidate'))
?.match(/\d+\.\d+\.\d+\.\d+/)?.[0];
return {
publicIP,
localIP,
behindNAT: publicIP !== localIP
};
}IPv4 Geolocation
IP-Based Location Lookup
interface IPv4Location {
ip: string;
country: string;
countryCode: string;
region: string;
city: string;
latitude: number;
longitude: number;
isp: string;
timezone: string;
}
async function geolocateIPv4(ip: string): Promise<IPv4Location> {
const response = await fetch(`https://ipapi.co/${ip}/json/`);
return response.json();
}
// Usage with proxy
const location = await geolocateIPv4('8.8.8.8');
console.log(`IP ${location.ip} is in ${location.city}, ${location.country}`);IPv4 vs IPv6
Key Differences
interface ProtocolComparison {
ipv4: {
addressSize: 32; // bits
format: '192.0.2.1';
totalAddresses: '4.3 billion';
header: '20-60 bytes';
security: 'Optional (IPsec)';
configuration: 'DHCP or manual';
};
ipv6: {
addressSize: 128; // bits
format: '2001:0db8::1';
totalAddresses: '340 undecillion';
header: '40 bytes (fixed)';
security: 'Built-in (IPsec)';
configuration: 'Auto (SLAAC)';
};
}Best Practices
For Developers
- Always validate IPv4 format before use
- Handle both IPv4 and IPv6 in applications
- Use CIDR notation for network ranges
- Implement proper error handling for IP operations
For Network Configuration
- Use private ranges for internal networks
- Implement NAT for address conservation
- Plan for IPv6 transition
- Monitor IP address allocation
