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The existence of these users is unfortunately causing content providers to put off enabling IPv6. For more information, see these presentations by Yahoo (https://sites.google.com/site/ipv6implementors/2010/agenda/07 Fesler Y\!atGIPv6ImpConf.pdf?attredirects=0), Google, and Redpill Linpro. There's also an article about the problem in Wikipedia.

This section attempts to document the most common causes as to why this happens, and how end users can solve it. It is based on real operational experience from running dual-stacked web sites.

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6to4 router functionality is implemented and often enabled by default in a large number of home gateway products made by several different vendors. This is unfortunately in accordance with Microsoft's requirements for Windows-compatible home routers. Due to the fact that not all operating systems and applications de-prefer transitional IPv6 connectivity, it is recommended to disable it (especially 6to4) whenever possible.

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The GNU C Library will de-prefer transitional IPv6 connectivity if the local IPv4 address is not a private one (RFC 1918), due to a strict interpretation of RFC 3484 (see SW#11438).

Solution: Upgrade the Linux distribution to Debian Squeeze, Fedora 13 Goddard, Ubuntu 10.04 Lucid Lynx, Mandriva 2010.1 Spring, openSUSE 11.3, Gentoo 2010-04-25, or any later versions.

Alternative solution: Add the following lines to the file /etc/gai.conf (create it if it doesn't exist):

Code Block

scopev4 ::ffff:169.254.0.0/112  2
scopev4 ::ffff:127.0.0.0/104    2
scopev4 ::ffff:0.0.0.0/96       14

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Solution: Disable 6to4 and Teredo, by entering the following commands in an Administrator shell:

Code Block

netsh interface ipv6 6to4 set state disabled
netsh interface teredo set state disabled

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This will especially affect users of Mozilla Firefox older than version 4.0, as it will request AAAA records even though the system does not have any global IPv6 addresses (see bug #614526), and will attempt to connect to the IPv6 addresses in preference to falling back to IPv4. Safari also suffered from this problem up until Mac OS X 10.6.4. It will also affect users of the virtualisation software Parallels Desktop (regardless of the browser used), because its virtual network interfaces have site-local IPv6 addresses assigned, in turn making the AI_ADDRCONFIG flag to getaddrinfo() ineffective.

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Mozilla Firefox does not set the AI_ADDRCONFIG flag when looking up names using the system getaddrinfo() library function, which causes it to solicit AAAA records even though the system has no IPv6 addresses (non-loopback and non-linklocal). This can trigger other problems, such as the D-Link AAAA mangling bug and the Mac OS X bug regarding the use of link-local IPv6 addresses when connecting to global destinations. The bug is fixed as of Firefox 4.0, see the bug report

Solution/work-around: Upgrade to Firefox version 4.0.

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The NTT Next Generation Network includes the physical last-mile infrastructure (the local loop) to the customer's premises. Other ISPs lease these lines in order to provide internet service, similar to a LLU arrangement.

However, the NGN infrastructure also includes a walled-garden IPv6 deployment, which is used to deliver IPTV services, at least. While this IPv6 connectivity cannot communicate with the Internet at large, it uses globally scoped IPv6 addresses that looks just like ordinary IPv6 internet connectivity to the devices on the residential LAN. To compensate for this, the NGN centrally spoofs TCP RST packets for all connections that attempt to cross the walled garden boundary and get out to the global Internet. While this limits the impact on end users, it still is known to cause at least 1-second connection timeouts and failed image loading on (older) MSIE browsers. There's also a concern that the central TCP RST generators won't be able to keep up with the load, once a significant number of popular destinations on the Internet deploy IPv6.

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Work-around: Install a modified RFC 3484 policy table that specifically de-prefers the use of the NGN IPv6 prefixes for communication with global destinations, see http://www.attn.jp/maz/p/i/policy-table/ for for more information.

Alternate work-around: Disable IPv6 in the operating system.

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