To elaborate other commenter's reference to XLAT: There is an IPv6 address block assigned for "IPv4-translated" address (::ffff:0:$IP4ADDR). In networks that s

To elaborate other commenter's reference to XLAT: There is an IPv6 address block assigned for "IPv4-translated" address (::ffff:0:$IP4ADDR). In networks that support this, packets destined for these addresses are routed to a NAT64 box for introduction to the v4 internet. Like all NAT-based solutions, this only provides support for outgoing connections out of the box, but that's unavoidable without assigning v4 addresses to hosts, and in the consumer ISP use case is all you need anyway.