IPv6 : Win7 vs Win8

Just an update: I eyeballed the “PrefixPolicies-Vista78.cmd” script from

https://sites.google.com/site/jrey42/Home/ipv6/prefixpolicies, concluded

that it was safe, and ran it. It apparently works, but I don’t have a

ULA setup to test it with.

jrey42 deserves kudos.



On 21/12/2015 07:57, Brian E Carpenter wrote:

On 21/12/2015 03:28, Marc Luethi wrote:

Hi all

I suggest to investigate source address selection on the client side,

while closely following name resolution (assuming this is similar to

Windows 2012R2’s DA implementation, DNS64 is supposed to be at work, here)

and keeping an eye on the IPv6 routing table.

In your situation, I would presume that the end system ends up with an RFC

4193 address (from the /48 that was initially chosen when DA was set up) on

its *IP-over-HTTPS* tunneling interface (courtesy of the DA implementation)

and a global unicast address  the (W)LAN interface, based on the CPE’s RAs.

While things *should* be neat, my experience with Windows 7’s way of

picking source addresses was so bad (“longest match” seemed entirely

unheard-of), I eventually gave up using RFC 4193 addresses for my internal

network altogether.

I repeateadely observed Win7 using its global unicast address(es) to access

internal ressources, while stubbornly sticking to te RFC4193 source address

when attempting to talk to addresses on the global IPv6 internet.

Yes. Apparently Win8 is up to date in that respect (i.e. follows RFC6724 not

RFC3484). It would be possible to make Win8 misbehave by changing the default

preferences (https://tools.ietf.org/html/rfc6724#section-10.6).

Conversely, it’s possible to make Win7 behave correctly by changing its default

policies to conform to RFC6724. I just found the following site that offers a

script (YMMV, I haven’t checked it):


But if that is the cause of the original issue, maybe switching off the

ULA prefix would be easier, and nicer than switching off IPv6.

     Brian Carpenter



On 19 December 2015 at 22:37, Kurt Buff  wrote:


I ran into an interesting situation some months ago which still

baffles me, and though I was able to work around it, I expect it will

happen again.

We implemented MSFT DirectAcess at our company quite some time ago

(using 2008R2 and Forefront 2010), and it works extremely well.

At least it worked well for everyone until one of the employees got

his Comcast connection upgraded, and then DirectAccess didn’t work for

that employee any more.

We proved that if he tethered to his cell phone, that would work, and

if he used an SSL VPN client while on his Comcast connect that would

work, but DirectAccess would not work at home.

Finally, I discovered that his Comcast-installed router was handing

our IPv6 addresses on his home LAN. Turning that off enabled

DirectAccess to work again.

We do not have an assigned IPv6 block from our ISP, though of course

MSFT OSes use it, and auto-assign themselves addresses, but for now

we’re ignoring it.

Has anyone run into this problem and solved it – not by turning off

iIPv6 address assignment for the home LAN, but really solved it? If

so, how did you do that?

Would getting and implementing an IPv6 assignment from our ISP cure

the problem, or make it worse?

I’ve found little guidance from MSFT about DirectAccess in an IPv6

environment, though I admit I haven’t been terribly diligent in my