``True`` if the address is defined as globally reachable by
iana-ipv4-special-registry_ (for IPv4) or iana-ipv6-special-registry_
(for IPv6) with the following exception:
For IPv4-mapped IPv6-addresses the ``is_private`` value is determined by the
semantics of the underlying IPv4 addresses and the following condition holds
(see :attr:`IPv6Address.ipv4_mapped`)::
address.is_global == address.ipv4_mapped.is_global
``is_global`` has value opposite to :attr:`is_private`, except for the ``100.64.0.0/10``
IPv4 range where they are both ``False``.