The SixXS IPv6Gate/IPv4Gate, sometimes just called IPv6Gate or IPv4Gate depending on the flavor in use, is a free IPv6 to IPv4 (IPv6Gate) and IPv4 to IPv6 (IPv4Gate) web proxy. It provides access to IPv6 websites from an IPv4 address and vice versa to IPv4 websites from an IPv6 address. It thus acts as a gateway to either IPv4 or IPv6, hence the IPv6Gate.
How to use it
The IPv6Gate works by either appending .sixxs.org or ipv6.sixxs.org or ipv4.sixxs.org depending on if one wants to access IPv4 websites from an IPv6 address or IPv6 websites from an IPv4 address.
To access an IPv4 website from an IPv6 address (thus that your computer has an IPv6 address), one simply has to add .sixxs.org to the hostname in the site's URL. So, for example, http://en.wikipedia.org/wiki/Main_Page becomes http://en.wikipedia.org.sixxs.org/wiki/Main_Page. The latter is known as a IPv6Gated link. One can also append .ipv6.sixxs.org similar to the usage of the IPv4Gate thus http://en.wikipedia.org.ipv6.sixxs.org/wiki/Main_Page.
To access an IPv6 website from an IPv4 address (thus that your computer has an IPv4 address), one simply has to add .sixxs.org to the hostname in the site's URL. So, for example, http://www.kame.net becomes http://www.kame.net.ipv4.sixxs.org. The latter is known as a IPv4Gated link. The KAME website is often used as an example of an IPv6 website due to the Dancing KAME ("Kame" is Japanese for turtle).
How it works
The complete .sixxs.org Domain name points to a set of servers that translate requests that end in .sixxs.org to either their IPv4 or IPv6 equivalents. The translation includes rewriting all of the links inside the page so that when following a link the link stays inside the .sixxs.org domain, thus keeping you on the proxy and thus allowing one to browse sites.
The project was launched publicly on 28 January 2003 Since then tweaks have been applied to let it better function with various websites like Slashdot, Wikipedia and others.
The IPv6Gate was featured twice on Slashdot in February 2003 ("Slashdot over IPv6") and January 2009 ("http://tech.slashdot.org/article.pl?sid=09/01/08/1330216") but didn't get slashdotted.
The IPv6Gate acts like a proxy from IPv6 to IPv4 and vice versa. As it acts like a proxy it also supplies Via: and X-Forwarded-For headers.
The UserAgent will also contain "ForwardedFor/xxx" where xxxx is the IPv4 or IPv6 address of the originating host.
In case of abuse problems, don't hesitate to contact firstname.lastname@example.org with proper details (logs, timestamps etc etc) and we will resolve the problem as quickly as possible. Also see SixXS Contact Abuse for more details.
Currently Known Problems
The following problems are known by SixXS:
.sixxs.org URLs in Wikipedia/Wikimedia Blacklisted
Referencing .sixxs.org URLs is Meta-blacklisted. We don't consider this as an issue as all the content under *.sixxs.org is available at the original URL. This was at first because IPv6Gate was broken for some time, which has since then been fixed. Now the block is in place because it can otherwise be used to easily circumvent other blocks.
Editing of Wikipedia Blocked
Due to some people trying to put useless things on this talk page from the IPv6Gate and WP not supporting the IPv6 XFF thus unable being to distinguish users, the editing Wikipedia has been blocked. Request for block which has been granted for 5 years per 2009-01-26.