Public vs Private IP Addresses

The main difference

A public IP address is reachable through internet routing and is presented by a provider, gateway, VPN, or hosting network. A private IP address is intended for communication inside a local network.

Private addresses are not globally unique. Millions of homes can use 192.168.1.10 at the same time because routers keep those networks separate.

Common private address ranges

IPv4 private ranges include 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. IPv6 uses unique local addresses from fc00::/7 for similar private-network purposes.

Loopback and link-local addresses are also non-public, but they serve different technical roles and should not be described as ordinary private LAN ranges.

How NAT connects private devices

A NAT gateway rewrites address and port information so several private IPv4 devices can share a public address. Websites usually see the gateway address, not the laptop or phone's private address.

Carrier-grade NAT can add another sharing layer at the provider, causing several customers to appear under one public IPv4 address.

Security implications

Private addressing is not a security boundary by itself. Firewalls, secure configuration, updates, authentication, and network segmentation remain necessary.