What Is an IP Address?
Understanding IP Addresses
An IP address (Internet Protocol address) is a unique numerical label assigned to every device connected to a computer network that uses the Internet Protocol for communication. Think of it as a postal address for your device - it tells other devices where to send data so it reaches the right destination.
Every time you visit a website, send an email, or stream a video, your device uses its IP address to communicate with servers across the internet. Without IP addresses, data packets would have no way of knowing where to go.
IPv4 vs IPv6 Format
IPv4 addresses are written as four decimal numbers separated by dots, each ranging from 0 to 255. For example: 192.168.1.1. Each number represents 8 bits (an octet), giving IPv4 a total of 32 bits.
IPv6 addresses are written as eight groups of four hexadecimal digits separated by colons. For example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334. IPv6 uses 128 bits, providing a vastly larger address space.
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address Length | 32 bits | 128 bits |
| Format | Dotted decimal (192.0.2.1) | Hexadecimal colon (2001:db8::1) |
| Total Addresses | ~4.3 billion | ~340 undecillion |
| Example | 203.0.113.50 | 2001:db8::8a2e:370:7334 |
Public vs Private IP Addresses
A public IP address is globally unique and routable on the internet. It is the address that websites and external services see when you connect. Your Internet Service Provider (ISP) assigns you a public IP.
A private IP address is used within local networks (home, office) and is not directly accessible from the internet. Devices on your home Wi-Fi each have a private IP, and they share one public IP through a process called NAT (Network Address Translation).
| Type | Range | Use |
|---|---|---|
| Private (Class A) | 10.0.0.0 – 10.255.255.255 | Large enterprise networks |
| Private (Class B) | 172.16.0.0 – 172.31.255.255 | Medium-sized networks |
| Private (Class C) | 192.168.0.0 – 192.168.255.255 | Home and small office networks |
| Loopback | 127.0.0.0 – 127.255.255.255 | Testing on your own machine |
IP Address Classes
The original IPv4 addressing scheme divided addresses into five classes based on the leading bits of the first octet:
- Class A (1–126): Large networks - supports 16 million hosts per network
- Class B (128–191): Medium networks - supports 65,534 hosts per network
- Class C (192–223): Small networks - supports 254 hosts per network
- Class D (224–239): Reserved for multicast
- Class E (240–255): Reserved for experimental use
Modern networking largely replaces classful addressing with CIDR (Classless Inter-Domain Routing), which allows more flexible allocation of IP address blocks using prefix notation like /24 or /16.
Who Assigns IP Addresses?
IP address allocation follows a hierarchical system managed by several organizations:
- IANA (Internet Assigned Numbers Authority) - oversees global IP address allocation and delegates blocks to Regional Internet Registries.
- RIRs (Regional Internet Registries) - five organizations manage IP distribution in their respective regions:
- ARIN - North America
- RIPE NCC - Europe, Middle East, Central Asia
- APNIC - Asia-Pacific
- LACNIC - Latin America and Caribbean
- AFRINIC - Africa
- ISPs (Internet Service Providers) - receive blocks from RIRs and assign individual addresses to end users, either statically or dynamically via DHCP.