IPv6 unicast addresses can be aggregated with prefixes of arbitrary bit-length similar to IPv4 addresses under Classless Inter-Domain Routing (CIDR).

There are two types of unicast addresses in IPv6:

• Global unicast
• Link-local unicast

There is also a special-purpose subtype of global unicast:

• IPv6 addresses with embedded IPv4 addresses

Additional address types or subtypes can be defined in the future.

A unicast address has the following format:

Figure 1. Unicast address format