Teredo 'link' -

Network administrators love blocking things. They might block ports 80, 22, or 443. But if they forget to block Teredo (UDP port 3544), a user can tunnel any traffic out.

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. teredo

netsh interface teredo set state client

While other tunneling protocols (like 6to4) existed, they had a fatal flaw: They didn't work if you were behind a NAT. Network administrators love blocking things

Obfuscation (XOR with 0xFFFFFFFF ) prevents address scanning and simplifies NAT traversal. Teredo provided a necessary, albeit complex, solution for

ping -6 ipv6.google.com