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So my router was acting up so I decided to take a look at it. When I looked at the port forwarding rules I found about 300 Terredo port forwards. When I deleted them everything worked fine on my router and on my computer. I did so research and all I could find is that Terredo has something to do with ipv6 and tunneling, I can not find anything more. Can someone please tell me what it is besides the fact that it has something to do with ipv6 and tunneling. I would also like to know how to disable it.

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You need to find out which program is using Terredo to open up ports in your router. – Scott Chamberlain Jul 22 '13 at 4:59
@ScottChamberlain: That is irrelevant. Windows sets up the tunnel automatically, programs cannot ask for it. – grawity Jul 22 '13 at 5:50
@grawity utorrent does something special with Teredo, I don't know what it is doing though. – Scott Chamberlain Jul 22 '13 at 5:52
@ScottChamberlain: It does nothing more than install general IPv6 support system-wide (including Teredo), like netsh interface ipv6 install. The button is there because Windows XP didn't have IPv6 support enabled by default. After enabling IPv6, however, all tunnels (6to4, Teredo, ISATAP) are set up automatically. – grawity Jul 22 '13 at 5:54
@grawity after reading your answer I came to that conclusion on my own too (good answer +1 btw) – Scott Chamberlain Jul 22 '13 at 5:55
up vote 1 down vote accepted

Yes, Teredo (one 'r') is an IPv6-over-IPv4 tunnel; in other words, it's a method to give IPv6 connectivity when your ISP only provides IPv4. It works by putting all IPv6 packets inside UDP and sending them over IPv4 to a "proxy" server at Microsoft, which resends them directly over IPv6.

There really isn't much more to say about it. Windows automatically sets up a tunnel when it doesn't find a native IPv6 connection, using 6to4 when possible and Teredo otherwise.

To disable Teredo on Windows XP and later, run this command:

netsh interface ipv6 set teredo disable

To re-enable Teredo (which you probably will never need):

netsh interface ipv6 set teredo client

(I won't describe how to disable IPv6 itself, because that is not necessary.)

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