Threat Level: green Handler on Duty: Didier Stevens

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Microsoft Teredo Server "Sunset"

Microsoft has offered a Teredo server to allow users behind NAT gateways to obtain an IPv6 connection. Teredo was always considered as a transition technology to obtain IPv6 connectivity is nothing else works to connect to a particular resource ("path of last resort"). With native IPv6 connectivity becoming more common, there will be less need for transition technologies like Teredo. 

As we reported earlier, the host name for Microsoft's Teredo server ( doesn't resolve currently. This is appearantly part of a "test" to measure the impact of the service being turned off. As an alternative, Microsoft still offers the "" hostname to connect to it's Teredo servers. To adjust your settings, use:

netsh interface teredo set state client

Of course, one may argue that with native IPv6 connecitvity becoming more common, transition technologies like Teredo will be more important for those of us left out in the legacy internet.

Thanks to our reader Gebhard for pointing out these URLs with more details:

Johannes B. Ullrich, Ph.D.
SANS Technology Institute

I will be teaching next: Defending Web Applications Security Essentials - SANS Cyber Defense Initiative 2021


4301 Posts
ISC Handler
Jul 12th 2013

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