Teredo (also known as IPv4 network address translator (NAT) traversal for IPv6) is designed to make IPv6 available to IPv4 hosts through one or more layers of NAT by tunnelling packets over UDP. It is a host-to-host automatic tunnelling mechanism that provides IPv6 connectivity, when dual-stack hosts are located behind one ore multiple NATs by encapsulating IPv6 packets in IPv4-based User Datagram Protocol (UDP) messages.