Public IP
Globally routable IP address used to communicate over the public internet.
A public IP address is an IP address that is visible and reachable on the global internet. It is the address other systems on the internet — websites, mail servers, peers — see when they communicate with a network, and it is what makes routing across the internet backbone and between ISPs possible.
Public IPs differ fundamentally from a Private IP: private addresses live inside a local network and are not routable on the internet. In typical IPv4 deployments many devices behind a router share a single public IP through NAT, which translates internal addresses and ports into the one public address.
A public IP can be either static (manually assigned and stable over time) or dynamic (changing periodically, typically handed out by the ISP via DHCP). Some ISPs also use Carrier-Grade NAT (CGNAT), where many customers share a smaller pool of public IPs, which can affect inbound connectivity.
Public addressing exists in both IPv4 and IPv6. IPv6 dramatically increases the available public address space, making it practical for every device on a network to have its own globally routable address without NAT.
Points clés
- Reachable from the public internet
- Assigned by ISPs
- Can be static or dynamic
- Used for websites, servers and internet access
- Often shared through NAT in IPv4 networks
- Required for inbound internet communication
- Visible to external systems and services
- IPv6 greatly expands public address availability