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

Karl Auer kauer at biplane.com.au
Thu Oct 18 15:33:28 CEST 2012

[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

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

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.

Karl Auer (kauer at biplane.com.au)

GPG fingerprint: AE1D 4868 6420 AD9A A698 5251 1699 7B78 4EEE 6017
Old fingerprint: DA41 51B1 1481 16E1 F7E2 B2E9 3007 14ED 5736 F687

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