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UDP 3544

ProtocolUDP
Port3544
LabelsTeredo tunneling

Synopsis

  • UDP port 3544 is used by Teredo, Microsoft’s IPv6-over-IPv4 tunneling protocol for NAT traversal.
  • Windows (Vista through Windows 11) includes a Teredo client (“Teredo Tunneling Pseudo-Interface” via the IP Helper service) that talks to Teredo servers such as teredo.ipv6.microsoft.com on UDP 3544.
  • Xbox One and Xbox Series consoles use Teredo on UDP 3544 for multiplayer and party chat when native IPv6 isn’t available (“Teredo is unable to qualify” errors occur when it’s blocked).
  • Miredo, an open-source Teredo implementation for Linux/Unix, uses UDP 3544 to reach servers like teredo.remlab.net.
  • Microsoft DirectAccess clients historically used Teredo over UDP 3544 as one of the transition methods to reach corporate resources.
  • Security note: Because Teredo encapsulates IPv6 inside UDP 3544, it can bypass IPv4-only firewalls and has been abused for NAT traversal and covert tunneling, so many organizations disable Teredo or block UDP/3544.

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