Teredo tunneling

The Teredo Tunneling protocol IPv6 over User Datagram Protocol through NAT protocol defines a method to access the IPv6 Internet from behind a NAT device. It consists of encapsulation IPv6 packets through User Datagram Protocol over IPv4 between Teredo clients and Teredo relays , with the help of Teredo servers .

= Purpose =

The IPv4 address exhaustion of IPv4 addresses has caused many home users to have multiple computers behind a NAT, using a single IPv4 public IP address. However 6to4, the most common IPv6 over IPv4 tunneling protocol, requires the client to have a public IPv4 address. Teredo makes it possible for IPv4 hosts behind NATs, many of whom cannot use 6to4, to have IPv6 connectivity through tunneling.

= Specification =

Teredo is referred to in employee working on IPv6.

= Implementations =

There are several known implementations of Teredo :

Microsoft s Teredo client and host-specific relay is included in Windows XP SP2 (first appeared in the Advanced Networking Pack for Windows XP SP1).

Microsoft provides a Teredo server and relay for Windows 2003 under the Microsoft Beta program.

[http://www.lip6.fr/ LIP6] and [http://www.6wind.com/ 6WIND] created ng_teredo, a Teredo server and relay based on Netgraph for FreeBSD.

Miredo is a GPL d Teredo client/relay/server Userland implementation for Linux and *BSD.

[http://sourceforge.net/projects/nici-teredo/ NICI-Teredo] consists of a Teredo relay for the Linux kernel and a userland Teredo server, developed at the Northern Taiwan Computer University.

= Servers and relays =

: For a complete explanation, see Teredo Overview in External Links.

A Teredo client is a host which has IPv4 connectivity to the internet from behind a NAT and uses the Teredo tunneling protocol to access the IPv6 internet. A Teredo client must communicate with two kinds of host :

Teredo servers are used to help the client initialize the tunnel and for configuration. However, a Teredo server never forwards any traffic for the client (apart from IPv6 pings). A Teredo server can support many clients.

Teredo relays are the hosts which are actually at the other end of the tunnel. They must forward all of the data part of the IPv6 transaction, and therefore require a lot of bandwidth and cannot support a very large number of clients.

= Current Teredo Server and Relay Status =

=== Teredo Servers ===

Maintaining a Teredo server requires little bandwidth and no particular rights, except that of emitting IPv6 packets with a source address belonging to the Teredo prefix, and two public IPv4 addresses, so potentially many people could host their own.

There are a few known Teredo servers:

teredo.ipv6.microsoft.com is the default server for Windows clients

teredo.via.ecp.fr (Miredo implementation)

teredo.ipv6.wanadoo.fr (for Wanadoo customers only)

203.233.154.10 (seemingly running ng_teredo)

formerly teredo.ipv6.6wind.com (testbed for ng_teredo)

=== Teredo Relays ===

On the other hand, a Teredo relay not only requires a lot of bandwidth, but for it to work with any particular IPv6 host, this host must have a route pointing to it for 3ffe:831f::/32 addresses. In practice, this means that you can set up a private Teredo relay for, e.g., your company or University campus, but having a worldwide Teredo relay requires being able to export BGP routes. Only large internet service providers can do this.

Note that Microsoft is not offering this service. Microsoft s idea was that each internet service provider would run its own relay for its own customers. However, to guarantee Teredo will work with any host, there must be at least one global Teredo relay. Without this, using Teredo is pointless because it might not always work.

In the beginning of 2005 there was a working Teredo relay located in South Korea. It now seems to be down. Currently the only BGP route pointing to 3ffe:831f::/32 addresses is owned by France Télécom (on their OpenTransit network) but its Teredo relay is private and can only be used by Wanadoo customers (see [http://www.ipv6.wanadoo.fr/ Wanadoo s IPv6 experimentation]).

= How to use Teredo =

== Why use Teredo ==

You need access to the IPv6 Internet

You have access to the IPv4 Internet

You are behind a NAT (e.g. home router or firewall)

== When should you not use Teredo ==

If you have a native IPv6 connection

If you have direct access to IPv4 Internet with a public IP address (in this case, use 6to4)

If you are behind a symmetric NAT, which is not compatible with the Teredo tunneling protocol

== What do you need ==

One of the following:

Windows XP SP2

Linux with miredo installed (see external links)

== How to use Teredo ==

Under Windows:

Open a command prompt (from Start Menu)

Install IPv6: ipv6 install

Set Teredo on: netsh interface ipv6 set teredo client teredo.ipv6.microsoft.com 30 (or use on the servers given above)

Test it: ping6 www.kame.net

Under Linux:

See miredo README file

== Alternatives to Teredo ==

If you have a public IPv4 address, use 6to4

If you are behind a NAT or not and live in Europe or the US, you could try using a [http://www.sixxs.net/ SixXS] tunnel, or in only North America, a [http://www.freenet6.net/ Freenet6] tunnel, situated in Canada.

Any other IPv6 tunneling method (e.g. IPv6-over-HTTP can even be used from behind a proxy)

= See also =

6to4

Tunneling protocol

= External links =

[http://www.microsoft.com/technet/prodtechnol/winxppro/maintain/teredo.mspx Teredo Overview] by Microsoft

[http://www.ietf.org/internet-drafts/draft-huitema-v6ops-teredo-05.txt The draft Teredo specification]

[http://www-rp.lip6.fr/teredo/ ng_teredo home page] by 6WIND and LIP6

[http://www.simphalempin.com/dev/miredo/ Miredo home page]

[http://sourceforge.net/projects/nici-teredo/ NICI Teredo] Sourceforge project