FRITZ!Box 6490 Cable Service - Knowledge Base

FRITZ!Box 6490 Cable Service

Cannot establish connections using the Teredo protocol

You cannot use the FRITZ!Box's Internet connection to establish connections using the Teredo protocol. This means that you cannot use Easy Connect with Windows Remote Assistance or establish DirectAccess connections, for example.


  • When an IPv6 Internet connection is active, for security reasons the FRITZ!Box blocks UDP port 3544. This means that applications cannot use the Teredo protocol to access the Internet and then bypass the FRITZ!Box's firewall and establish their own IPv6 connection using Teredo instead of using the FRITZ!Box's existing IPv6 connection. Thus, the FRITZ!Box complies with standardized recommendations for home network devices (RFC 6169 Section 3.1.3).

    Note:Teredo (RFC 4380) is an IPv6 tunneling mechanism devised to facilitate the transition from IPv4 to its successor IPv6. Teredo encapsulates IPv6 data packets from Windows computers within IPv4 data packets and transmits these to a Teredo server from Microsoft. This server then forwards the IPv6 data packets to their actual destination.

Important:Some of the settings described here are only displayed if the advanced view is enabled in the user interface.

1 Configuring an application for use without Teredo

  • Configure the Internet application so that it uses the IPv6 protocol instead of Teredo.

    Note:You can find information on using the application without the Teredo protocol and the necessary settings in the relevant documentation, or you can contact the manufacturer.


If the Internet application cannot be used without the Teredo protocol, you can disable the Teredo filter in the FRITZ!Box instead:

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Filters" in the "Internet" menu.
  3. Click on the "Lists" tab.
  4. Disable the option "Teredo filter enabled".
  5. Click "Apply" to save your settings.