I’ve just spent an hour struggling with (I thought) IPv6 on Windows 7. IPv6 is enabled by default on Windows 7. I was seeing autoconfigured addresses on the ethernet interface, but there was no IPv6 connectivity beyond that. Looking at it with Wireshark, I could see neighbor discovery packets leaving, but answer came there none. No firewall rules were blocking ICMPv6; in desperation I turned the firewalls OFF on both source and destination test machines – still nothing. What the…?

I should point out at this point that the Windows 7 machine was actually a virtual machine, running in VirtualBox on Linux. I should further point out that the host Linux machine had full dual-stack connectivity, and that everything was working swimmingly. It always has – the host is my main day-to-day workhorse, and I use IPv6 every day, for practically everything – mounting remote drives, logging into remote consoles, printing, emailing… It’s all done with IPv6 from this exact machine. The virtual machine had it’s “Local Area Connection” as a bridged adapter onto the connected interface of the host. The host’s connected interface was wlan0 – a wireless interface.

After this build-up, you probably think there’s a happy ending. Sadly, there’s not. IPv6 on the virtual does not work over the host’s wireless interface, in spite of the host being fully functional on that interface. When I connected the host to my network with an ethernet cable instead, and put the VM on eth0 instead of wlan0, all the problems with the virtual went away – perfect IPv6 connectivity.

After trying many things, I finally bewailed the problem on the Ubuntu Users mailing list. Within an hour, someone (thanks, sktsee) had pointed out this paragraph in the VirtualBox manual:

On Linux hosts, functionality is limited when using wireless interfaces for bridged networking. Currently, VirtualBox supports only IPv4 over wireless. For other protocols such as IPv6 and IPX, you must choose a
wired interface.

So – another speedbump on the road to IPv6! Hope Oracle gets into gear on this soon. A virtualisation technology that can’t do IPv6 is not going to be around for long.