The IPv4 over IPv6 tunneling technology enables communication between isolated IPv4 networks over existing IPv6 networks. IPv4 packets can be transparently transmitted over IPv6 networks after being encapsulated into IPv6 packets.
During the later transition phase from IPv4 to IPv6, IPv6 networks have been widely deployed, and IPv4 sites are scattered across IPv6 networks. It is not economical to connect these isolated IPv4 sites with private lines. The common solution is the tunneling technology. With this technology, IPv4 over IPv6 tunnels can be created on IPv6 networks to enable communication between isolated IPv4 sites through IPv6 public networks.