Teredo IPv6 tunneling server

 The Teredo IPv6 tunneling protocol encapsulates IPv6 packets into UDP/IPv4
 datagrams, to allow hosts behind NAT devices to access the IPv6 Internet.
 .
 Miredo-server provides a Teredo server. Teredo servers help Teredo clients
 determine their NAT configuration, maintain their NAT binding, and perform
 hole punching when transmitting IPv6 packets to other Teredo clients and/or
 Teredo relays.