The Complete Guide to IP Addresses

Every packet on the internet carries a source and destination IP. Routers use those addresses to forward packets hop-by-hop until they reach the destination network, where the local gateway translates and delivers to the right device.

Modern networks layer two address families on top of each other: IPv4 for legacy compatibility and IPv6 for scale. Most production services serve both, and your operating system picks whichever is faster via a process called Happy Eyeballs.

Public IPs are unique on the global internet. Private IPs repeat inside every home and office network. Network Address Translation (NAT) on your router rewrites the source IP of outgoing packets so dozens of private devices can share a single public address — the reason your phone, laptop, and TV all appear to come from the same IP on external tools.

Static assignments are configured manually; dynamic ones come from DHCP. CIDR notation (e.g./24) compresses the network mask, telling you how many addresses live in that block. A/24 has 256 addresses; a /16 has 65 536.

GeoIP databases map IP ranges to city, country, and ASN (Autonomous System Number — the network operator). Accuracy is best at the country level and degrades inside metro areas. ASN tells you whether traffic is residential, datacenter, mobile, or a known VPN exit — a critical signal for fraud and abuse decisions.