Today, it serves as a great case study in network engineering and a reminder that if left unmanaged.
IPv6 packet → UDP payload (IPv6 datagram) → IPv4 header (src: client private IPv4, dst: server/relay IPv4). UDP port 3544 (default). teredo
The exhaustion of the IPv4 address space necessitated the gradual deployment of IPv6. However, many end-user networks remain behind NATs, which disrupt traditional IP-in-IP tunneling (e.g., 6to4, configured tunnels). Teredo (RFC 4380, later updated by RFC 5991 and RFC 6081) solves this by encapsulating IPv6 packets within IPv4 UDP datagrams, allowing NAT traversal using techniques similar to UDP hole punching. Today, it serves as a great case study
To prevent Teredo damage, ship owners and marine engineers use a variety of methods, including: The exhaustion of the IPv4 address space necessitated
Teredo provided a necessary, albeit complex, solution for IPv6 connectivity in the era of pervasive NAT. Its main contribution is demonstrating that UDP encapsulation can successfully traverse NATs for layer-3 protocols. However, due to native IPv6 growth and security liabilities, Teredo is now considered a legacy technology. Network engineers should prefer native IPv6, 6to4 where applicable, or application-layer proxies.