[ipv6hackers] Win7 - no managed flag, DHCP address released?!?

Owen DeLong owend at he.net
Thu Oct 18 20:21:08 CEST 2012

I think that the behavior is within the letter of the law as it were for the RFCs, though I would agree not the best possible choice of actions.

However, two routers with disagreement in the M bit in the RAs they place on the same link is, IMHO, a misconfiguration to begin with and ill-defined or un-defined results should be expected in such circumstances.

You've just described current Windows ill-defined behavior in the face of such a misconfiguration. As much as I'd like to pick on Micr0$0ft, I would say that it is quite likely other systems do equally strange things in the face of such conflicting configuration information.


On Oct 18, 2012, at 06:33 , Karl Auer <kauer at biplane.com.au> wrote:

> [I sent this to the IETF list and they suggested I repost it here.]
> I have just seen the following demonstrated.
> Two routers, short RA interval, both sending RAs for the same prefix,
> both with the autoconf flag set, one with the managed flag set and one
> without.
> A Windows 7 host gets an address via DHCPv6 when the RA with the managed
> flag comes around - and DROPS IT when an RA without the managed flag
> comes past.
> This is not the valid lifetime expiring normally. I was not able to
> determine whether the Windows host is actually sending a DHCPv6 release
> as well, but it is most certainly dropping the address from the
> interface.
> I will be trying to do my own tests to confirm (or not) this behaviour,
> but has anyone else seen it? Or seen it with other operating systems?
> If it is indeed happening, this behaviour seems very badly broken to me.
> I don't feel the relevant RFCs can reasonably be interpreted as
> supporting this behaviour.
> Regards, K.
> -- 
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