IPv6 transition mechanisms
Standards Track
NAT64 / DNS64
Experimental
Informational
Drafts
Deprecated

Teredo Tunneling Pseudo Interface Driver for Windows 7 32 bit, Windows 7 64 bit, Windows 10, 8, XP. Uploaded on 3/26/2019, downloaded 5850 times, receiving a 84/100 rating by 4430 users. Microsoft Teredo Tunneling Adapter Driver for Windows 7 32 bit, Windows 7 64 bit, Windows 10, 8, XP. Uploaded on 3/29/2019, downloaded 4571 times, receiving a 76/100 rating by 2239 users.

In computer networking, Teredo is a transition technology that gives full IPv6 connectivity for IPv6-capable hosts that are on the IPv4Internet but have no native connection to an IPv6 network. Unlike similar protocols such as 6to4, it can perform its function even from behind network address translation (NAT) devices such as home routers.

Teredo operates using a platform independenttunneling protocol that provides IPv6 (Internet Protocol version 6) connectivity by encapsulating IPv6 datagram packets within IPv4 User Datagram Protocol (UDP) packets. Teredo routes these datagrams on the IPv4 Internet and through NAT devices. Teredo nodes elsewhere on the IPv6 network (called Teredo relays) receive the packets, un-encapsulate them, and pass them on.

Teredo is a temporary measure. In the long term, all IPv6 hosts should use native IPv6 connectivity. Teredo should be disabled when native IPv6 connectivity becomes available. Christian Huitema developed Teredo at Microsoft, and the IETF standardized it as RFC 4380. The Teredo server listens on UDP port 3544.

2Overview
5Security considerations

Purpose[edit]

The Microsoft Teredo Tunneling Adapter is the current method for Windows computers to work with both IPv4 and IPv6. It acts as a translator that interprets the two different IP address schemas so when you browse the web, you reach the website you want regardless of whether it has an IPv4 or IPv6 address.
The time when users start to see a yellow sign of exclamation on Device Manager close to the device Teredo Tunneling Pseudo-Interface and the status of this tool is “The device cannot start (Code 10).“, it means to say that your PC is unable to identify the driver currently present in your system.

6to4, the most common IPv6 over IPv4 tunneling protocol, requires that the tunnel endpoint have a public IPv4 address. However, many hosts currently attach to the IPv4 Internet through one or several NAT devices, usually because of IPv4 address shortage. In such a situation, the only available public IPv4 address is assigned to the NAT device, and the 6to4 tunnel endpoint must be implemented on the NAT device itself. Many NAT devices currently deployed, however, cannot be upgraded to implement 6to4, for technical or economic reasons.

Teredo alleviates this problem by encapsulating IPv6 packets within UDP/IPv4 datagrams, which most NATs can forward properly. Thus, IPv6-aware hosts behind NATs can serve as Teredo tunnel endpoints even when they don't have a dedicated public IPv4 address. In effect, a host that implements Teredo can gain IPv6 connectivity with no cooperation from the local network environment.

In the long term, all IPv6 hosts should use native IPv6 connectivity. The temporary Teredo protocol includes provisions for a sunset procedure: Teredo implementation should provide a way to stop using Teredo connectivity when IPv6 matures and connectivity becomes available using a less brittle mechanism. As of IETF89, Microsoft plans to deactivate their Teredo servers for Windows clients in the first half of 2014 (exact date TBD), and encourage the deactivation of publicly operated Teredo relays.

Overview[edit]

For a complete explanation, see Teredo Overview in External links.

The Teredo protocol performs several functions:

Diagnoses UDP over IPv4 (UDPv4) connectivity and discovers the kind of NAT present (using a simplified replacement to the STUN protocol)
Assigns a globally routable unique IPv6 address to each host using it
Encapsulates IPv6 packets inside UDPv4 datagrams for transmission over an IPv4 network (this includes NAT traversal)
Routes traffic between Teredo hosts and native (or otherwise non-Teredo) IPv6 hosts

Node types[edit]

Teredo defines several different kinds of nodes^[1]:

Teredo client: A host that has IPv4 connectivity to the Internet from behind a NAT and uses the Teredo tunneling protocol to access the IPv6 Internet. Teredo clients are assigned an IPv6 address that starts with the Teredo prefix (2001::/32).^[2]

Teredo server: A well-known host used for initial configuration of a Teredo tunnel. A Teredo server never forwards any traffic for the client (apart from IPv6 pings), and has therefore modest bandwidth requirements (a few hundred bits per second per client at most),^{[citation needed]} which means a single server can support many clients. Additionally, a Teredo server can be implemented in a fully stateless manner, thus using the same amount of memory regardless of how many clients it supports.

Teredo relay: The remote end of a Teredo tunnel. A Teredo relay must forward all of the data on behalf of the Teredo clients it serves, with the exception of direct Teredo client to Teredo client exchanges. Therefore, a relay requires a lot of bandwidth and can only support a limited number of simultaneous clients. Each Teredo relay serves a range of IPv6 hosts (e.g. a single campus/company, an ISP or a whole operator network, or even the whole IPv6 Internet); it forwards traffic between any Teredo clients and any host within said range.

Teredo host-specific relay: A Teredo relay whose range of service is limited to the very host it runs on. As such, it has no particular bandwidth or routing requirements. A computer with a host-specific relay uses Teredo to communicate with Teredo clients, but sticks to its main IPv6 connectivity provider to reach the rest of the IPv6 Internet.

IPv6 addressing[edit]

Each Teredo client is assigned a public IPv6 address, which is constructed as follows (the higher order bit is numbered 0):

Bits 0 to 31 hold the Teredo prefix (2001::/32).
Bits 32 to 63 embed the primary IPv4 address of the Teredo server that is used.
Bits 64 to 79 hold some flags and other bits; the format for these 16 bits, MSB first, is 'CRAAAAUG AAAAAAAA'. The 'C' bit was set to 1 if the Teredo client is located behind a cone NAT, 0 otherwise, but RFC 5991 changed it to always be 0 to avoid revealing this fact to strangers. The 'R' bit is currently unassigned and should be sent as 0. The 'U' and 'G' bits are set to 0 to emulate the 'Universal/local' and 'Group/individual' bits in MAC Addresses. The 12 'A' bits were 0 in the original RFC 4380 specification, but were changed to random bits chosen by the Teredo client in RFC 5991 to provide the Teredo node with additional protection against IPv6-based scanning attacks.
Bits 80 to 95 contain the obfuscated UDP port number. This is the port number that the NAT maps to the Teredo client, with all bits inverted.
Bits 96 to 127 contain the obfuscated IPv4 address. This is the public IPv4 address of the NAT with all bits inverted.

Teredo IPv6 addressing table

Bits	0 - 31	32 - 63	64 - 79	80 - 95	96 - 127
Length	32 bits	32 bits	16 bits	16 bits	32 bits
Description	Prefix	Teredo server IPv4	Flags	Obfuscated UDP port	Obfuscated Client public IPv4

As an example, the IPv6 address 2001:0000:4136:e378:8000:63bf:3fff:fdd2 refers to a Teredo client that:

Uses Teredo server at address 65.54.227.120 (4136e378 in hexadecimal)
Is behind a cone NAT and client is not fully compliant with RFC 5991 (bit 64 is set)
Is probably (99.98%) not compliant with RFC 5991 (the 12 random bits are all 0, which happens less than 0.025% of the time)
Uses UDP mapped port 40000 on its NAT (in hexadecimal not 63bf equals 9c40, or decimal number 40000)
Has a NAT public IPv4 address of 192.0.2.45 (not 3ffffdd2 equals c000022d,

Microsoft Teredo Tunneling Pseudo Interface