What is tunneling?
The basic technique for transporting IPv6 over IPv4 is tunneling, which involves encapsulating IPv6 packets in IPv4 packets so that they can be carried across IPv4 portions of the network. A tunnel is a link between two IPv4 end-points that must be configured by specifying the IPv6 destinations (an address or a prefix) for which the packets are to be encapsulated, and the remote IPv4 end-point to which they must be sent.

In the simplest case, the network administrator configures tunnels manually by agreement with the administrator of the network where the remote IPv4 end-point resides. This type of tunneling is usually called static tunneling. Most of the current interconnections between IPv6 networks used today are set up through static tunneling.