Moving to IPv6

Moving to IPv6 will be more of a transition or migration than a one-time event. As such, there are mechanisms in place to support coexistence between IPv4 and IPv6 including the ability for a router or network device to run both protocol stacks at the same time, and the ability to perform tunneling. A tunneling example would be when there are two isolated portions of the network that want to run IPv6, and between them, there is a big patch of IPv4 only. Tunneling would take the IPv6 packets and re-encapsulate them into IPv4 for transport across the IPv4 portion of the network. At the other end of the tunnel, the router would de-encapsulate the IPv6 from the IPv4 shell and then continue forwarding the IPv6 packet on toward its final destination.