IP address

An IP address is a numeric label assigned to every device on a network so other devices know where to send traffic. IPv4, defined in RFC 791, addresses are four decimal numbers separated by dots (like 203.0.113.42), drawn from a pool of about 4.3 billion addresses that ran out years ago — IANA’s IPv4 Address Space registry tracks exactly which /8 blocks were allocated and when — which is why ISPs now lean on techniques like CGNAT to stretch what remains. The RIPE NCC, the regional internet registry for Europe, the Middle East and parts of Central Asia, exhausted its remaining IPv4 pool in November 2019. IPv6, defined in RFC 8200, addresses are longer hexadecimal strings with a vastly larger address space, designed to give every device its own public address without sharing. Not every address is meant to be reached externally, though — the loopback address a device uses to address itself is one of several ranges carved out for a purpose other than ordinary internet-facing traffic. IPv6 also has its own private-addressing range for networks that want no part of the public internet at all: a ULA (Unique Local Address), generated locally rather than assigned by an ISP. Most internet services still see your IPv4 address, your IPv6 address, or both, depending on what your device and network support — AdminKit’s IP lookup, like Cloudflare’s own “What Is My IP Address?” explainer describes, shows exactly what the internet sees from your connection right now.