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I'm experimenting with network protocols a little bit and want to connect an IPv6 host from my IPv4-only internet connection using Teredo.

The computer is behind a NAT.

I tried different Teredo servers and I tried both Windows and Linux.

What I do is trying to establish a TCP connection (HTTP).

The result I observe in Wireshark is always the same:

  • My computer sends an initial ICMPv6 packet to the Teredo server
  • I receive the response - also an ICMPv6 packet
  • My computer sends multiple Ping (IPv6) packets
  • I never see an answer packet
  • After some time I get a time out
  • The "initial" ICMPv6 packet is repeated after some time and I see the answer.

Why is there no "ping" response from the IPv6 host (which are obviously neccessary for Teredo)?

--- Edit ---

After some more reading I can imagine that my Router is a "symmetric NAT" which is not supported by Teredo...

--- Edit 2 ---

... however I switched on "Port Forwarding" on my router for the UDP port that I use so a response should reach my computer even if it is sent from a different IPv4 address. And I switched off all firewalls.

Martin Rosenau
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  • What IPs are you trying to ping? – nKn Sep 17 '15 at 20:48
  • I tried both Google's IPv6 address as well as a German Computer Magazine which is "IPv6-ready" since 2012. – Martin Rosenau Sep 17 '15 at 20:53
  • Can you see your IPv6 configured in your OS? You don't mention whether you use Windows or Linux, but `ipconfig /all` and `ifconfig` respectively should give you information about the link and whether everything is woking fine. You could also provide what steps have you followed to configure the interface so someone might point you to the error. – nKn Sep 17 '15 at 20:59
  • I could post the `ipconfig /all` configuration but I think I have a completely other problem: According to Wireshark the Ping request is sent over the network card but the response is not arriving. If it was a problem with the configuration either the request would not be sent by the network card or the response would arrive but be ignored by the OS. – Martin Rosenau Sep 17 '15 at 21:08

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Teredo is not the protocol you want to use for this. Its reliability is very unpredictable and Microsoft has plans to sunset its Teredo service. If you want to use IPv6 but your ISP does not support it (shame on them) then you should get a tunnel from i.e. Hurricane Electric or SixXS. Those tunnel servers are operated by people who care about the service and connectivity they deliver.

Sander Steffann
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  • Thanks for that answer and +1. Indeed I explicitly wanted to do some tests with Teredo, not with IPv6 in general. In the end I wanted to find out if it would be possible to write intenet software (such as web browsers) having built-in Teredo support so IPv6 URLs could be used on old OSs not having IPv6 support at all or systems having IPv6 disabled. However now I found out that even the "official" Teredo implementation on my Windows 7 does not work... – Martin Rosenau Sep 18 '15 at 04:32