Global Unicast Address

Global Unicast Address

A Global Unicast address is a type of IPv6 address. These are addresses that are routable (or usable) on the internet.

This is a big change between IPv4 and IPv6. IPv4 commonly uses private IP addresses and NAT, so only a few devices are directly on the internet. IPv6 on the other hand, expects most devices to be globally routable.

Ranges of global unicast IPs are handed out to customers by their service providers, or by RIRs. These would commonly be /48 or /56 blocks. Large companies may even get blocks as big as /32. 

The allocated block is a ‘site prefix’. They cover the whole network. These prefixes are further divided into smaller subnet IDs. These are typically /64, but can be other sizes.

The rest of the address called the ‘Interface ID’, is available for hosts and devices.