Tunneling provides a mechanism to transfer IPv6 traffic through an IPv4–only network.
IPv6 tunneling encapsulates IPv6 packets in IPv4 packets for delivery across an IPv4 infrastructure.
At the tunnel source, or head end, the system encapsulates an IPv6 packet into an IPv4 packet and sends it to the remote tunnel destination.
The tunnel destination strips the IPv4 packet header and forwards the original IPv6 packet further into an IPv6 cloud.
These types of tunnels are called dual-stack tunnels because they support both IPv4 and IPv6.