What provides full IPv6 connectivity for hosts lacking a connection to a native IPv6 network?

Teredo is a tunneling protocol specifically designed to provide full IPv6 connectivity to hosts that are behind a NAT (Network Address Translation) device and do not have direct access to a native IPv6 network. It encapsulates IPv6 packets within IPv4 UDP datagrams, allowing these packets to traverse NAT devices.

When a host uses Teredo, it effectively creates a tunnel that enables IPv6 communication over an IPv4 infrastructure, making it possible for devices that lack a native IPv6 connection to still communicate using IPv6. This is particularly useful for internet-enabled devices that are in environments where maintaining a pure IPv6 setup is not feasible.

On the other hand, other options like 6to4 are also tunneling methods for IPv6, but they require a public IPv4 address and are generally not suitable for hosts behind NAT. Switch spoofing and ARP spoofing are related to vulnerabilities in network layers but do not facilitate IPv6 connectivity. Therefore, Teredo is the most appropriate choice for providing full IPv6 connectivity in the specified scenario.