What to do if you're broken...

If you are reading this page, it means that we've identified that your host will have problems on World IPv6 Day. Any web site that goes "dual stack" (meaning, both IPv4 and IPv6), will be unreachable to you.

To resolve this, you'll first need to identify your IPv6 address (if you have one) and your IPv6 default route (if you have one). This will help identify which sections to read.

If you find your particular problem is not well represented; or you have additional suggestions; please do leave feedback using the form (or contact jfesler@test-ipv6.com).

Show instructions for: [All] [Windows] [Mac OS X] [iPhone/iPad] [Linux]

Make sure you are current

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Many OS and Hardware manufacturers are making updates to help improve the transition to IPv6. Some known "gotchas" are being addressed by workarounds by these vendors.

You can do your part to make sure you are running the latest:

Finding your IP address

Show instructions for: [All] [Windows] [Mac OS X] [iPhone/iPad] [Linux]

Identify your IPv6 address, and your default router (if you have one).

Finding your IPv6 address and default router can be a challenge if you are not familiar with your OS's network configuration. Instructions for your OS are below.

When looking for your IPv6 address, skip any fe80: address. Everyone has them if their OS supports IPv6; this is regadless of whether or not your ISP supports IPv6 yet. Those are "link local" addresses; used just for communicating to other hosts in the same physical network as you.

OS X users: To find your IP address using the GUI:

OS X users: To find your IP address using the command line:

iPhone and iPad users: No information is shown via Apple's preferences/setup. The "IT Tools" and the "ip6config" apps do show IPv6 address data; both cost.

Linux users: To find your IPv6 address, open a terminal and..

Linux users: To find your IPv6 route, use:

Generic unix instructions for determining your IPv6 address and default route:

Windows users: To find your IP address using cmd.exe:

Windows 7 GUI users:

Other Windows based OS's: Send jfesler@test-ipv6.com detailed instructions; and I'll add them to the site.

If you set up a tunnel broker

If you set up a tunnelbroker tunnel: The most common causes for tunnelbroker users to fail are:

If you set up 6to4

(IPv6 address: starts with 2002)

If you use 6to4 (without a tunnel broker; ie, using anonymous 6to4):

The use of "automatic" 6to4, or the use of 6to4 without explicit configuration of the gateways, is not recommended. For more information see 6to4.

If you want to continue trying to debug anonymous 6to4:

If you have an ULA

(IPv6 address: starts with FC or FD)

ULA or Unique-Local-Unicast: If you have an IP address starting with FC or FD, you have what is effectively a private IPv6 address. It might be usable for talking to other devices within your home, or within your company. It also allows you to have a steady IPv6 address inside, even if your public IPv6 address changes regularly.

The main problem with ULA is that certain home routers are now offering ULA, *and* giving you a default route. This route is offered regardless of whether or not your router actually has IPv6 connectivity. From your browser's point of view, it doesn't know that your default route goes nowhere; there is no feedback mechanism. Since IPv6 is (roughly speaking) preferred over IPv4, your browser will try using this broken route. It may take minutes before giving up.

Our advice: Enable ULA only if your router has full time IPv6 connectivity. Disable it, otherwise. If you do disable it on your router, you will likely need to reboot your router first, then reboot your host, before the symptoms go away.

Bad or Inappropriate IPv6 Addresss

(IPv6 address: see table below)

Bad or Inappropriate IPv6 Addresses (Bogons): If you IPv6 address starts with any of these, your router needs to be upgraded.

fcxx: or fdxx:

AVM FritzBox - disable ULA.

Other routers: Try updating the firmware. If that fails, look for and disable "ULA" or "Unique Local Addressing".

If that fails, disable IPv6 entirely on the router.

2002:0Axx: or 2002:Axx:

This is a router using 6to4, but using a private IPv4 address. This will never work.

Apple routers: Update to the latest firmware; that has been corrected.

Other routers: Try updating the firmware. If that fails, look for and disable "6to4" or any form of automatic IPv6 tunnel.

If that fails, disable IPv6 entirely on the router.


This router is using the official "Documentation" prefix - which is not routable on the IPv6 Internet.

Cisco E2000, E3000, E4200: Update to the latest firmware.

Other routers: Try updating the firmware.

If that fails, disable IPv6 entirely on the router.


WRVS4400N routers: Disable IPv6.

Other routers: Try updating the firmware.

If that fails, disable IPv6 entirely on the router.

If you have an unexpected IPv6 address

(IPv6 address: not starting with fe80)

Unexpected IPv6 address?

Modern operating systems all have IPv6 enabled. This feature is dormant until someone explicitly configures IPv6, or a device on the local network offers it. Autoconfigured IPv6 hosts learn their IPv6 address and their gateway through the use of IPv6 router announcements (RAs). The network you are on may intentionally offer IPv6; you'll automatically use it when your computer sees it.

Where this goes wrong: Some people plug their router into the network (wired or wireless) and inadvertantly offer IPv6 services to everyone. Classic examples of this are where people add an early version of an Apple router (with 6to4 automatically enabled); another example is someone who has Windows Internet Connection Sharing enabled. In both cases, there is a chance they offer their services - and become your IPv6 router of choice, without any notification to you.

If these IPv6 routers don't work, you will fail to connect to any web site that offers services on both IPv4 and IPv6. Even if they do work, if the router in question is unplugged (the owner packs up, leaves the hotel/conference) your host never gets the notice; and it can be hours before it gives up.

This is similiar to someone accidentially (or intentionally) running a rogue DHCP server.

If you are are not the network admin - and have no access to fix the problem - consider disabling IPv6, at least for the location you are in. Another option might be to try turning off, and turning back on, your network interface (clearing the IP address), in case the source of the problem has left the network.

If you are the network administrator: You can use the default route information to identify the ethernet address; and then search for the owner of that ethernet address. Some network vendors have features that will suppress the advertisements of unauthorized RAs (router announcements); consider enabling those feaatures. More reactive measures involve finding (by ethernet address) the owner of the device; or possibly spoofing RA's from their device to indicate the device is going away.

If all else fails

Show instructions for: [All] [Windows] [Mac OS X] [iPhone/iPad] [Linux]

(Instructions for disabling or deprioritizing IPv6)

Disabling or Deprioritizing your IPv6 address

To disable IPv6 entirely, until your ISP offers IPv6 to you: see Microsoft's "fixit" site that gives clear instructions. We advocate considering "Use IPv4 instead of IPv6 in prefix policies", instead of completely disabling IPv6. Specific Windows features depend on IPv6 being enabled.

To completely disable IPv6 (Windows 7, Vista; XP should be similiar):

To disable IPv6 in Windows XP:

Other Windows based OS's: Send jfesler@test-ipv6.com detailed instructions; and I'll add them to the site.

OS X users

Before disabling IPv6, please be sure you are running the latest OS version. In particular, OS X 10.6.7 has several workarounds for being "Broken". This may solve your problems without resorting to completely disabling IPv6.

iPhone and iPad users

IPv6 is not configurable on the iPhone or iPad. Your only option is to switch to another network.

Linux users:

Generic unix instructions, to temporarily remove your IPv6 address.

See Also

Other resources that may help

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