VirtualBox flubs IPv6 (when in doubt, go wired)

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…?

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IPv6 Destination Address Selection – what, why, how

IPv6 destination address selection is the process of deciding which IPv6 address a connection should be made to. This is the flip side of IPv6 source address selection, which has been the subject of several earlier articles (start here). Destination address selection is described in the same RFC as source address selection – RFC 6724 (which obsoletes RFC 3484).

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Controlling IPv6 source address selection

In a previous article, I discussed how IPv6 source address selection worked. Normally it all Just Works, but there are several situations where you may want or need to control the address selection process. In this article, we’ll look at why you might want to control source address selection, and how you can do it.

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IPv6 Source Address Selection – what, why, how

Source address selection must be very irritated; destination address selection gets all the press coverage.

This article will start to redress the balance, by talking about what source address selection is, why it is needed, and how it works. If you want the nitty-gritty, check out RFC 6724 (which obsoletes RFC 3484).

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IPv6 ULA – what and how?

ULA (Unique Local Addresses, or Unique Local IPv6 Unicast Addresses to give them their full name) are IPv6’s equivalent of IPv4’s “private” addresses.

The idea is to append a random 40 bits to the reserved ULA prefix fd00::/8, thus building a /48 that you can call your own. You can use this /48 wherever and however you like, with the sole proviso that it must not be routed on the public Internet. The ULA space is defined in RFC4192 (

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