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

Jeff Carrell jeff.carrell at networkconversions.com
Thu Nov 8 15:56:35 CET 2012

Karl, I confirm. In fact, that is part of what my presentation was about 
and what I demonstrated at the conf there last month :-)

I have seen this occur on the Win7 clients with these router platforms: 
HP ProVision, HP Comware (old 3Com), Cisco, Vyatta, and plain radvd on 
Ubuntu. And generally I have a mix of routers running in the labs/demos.

The Win7 client had seen a RA with M on and sent a DHCPv6 Solicit and 
received their IPv6 DHCPv6 assigned address. Then when the client 
receives a subsequent RA with M off, the Win7 clients send a DHCPv6 
release and drops their previous DHCPv6 address...and do not wait for 
the timers that had been associated with that address to expire.

I don't remember how the Mac with 10.7.x reacted, but looking through a 
couple of trace files from my tests, it does not appear that it acts the 
same...it looks like it adheres to the timers accordingly. However, I 
would like to test it all again in my lab to see.

In fact, I'd like to do it again for Win7, Win8, Mac 10.7.x, Linux (I 
have a client somewhere with the DHCPv6 client appl on it), and get a 
more conclusive trace file on this all. However, it will be a week or so 
before I'll be able to do this.


On 11/08/2012 05:00, ipv6hackers-request at lists.si6networks.com wrote:
> Today's Topics:
>     1. Re: Win7 - no managed flag, DHCP address released?!? (Enno Rey)
> ----------------------------------------------------------------------
> Message: 1
> Date: Wed, 7 Nov 2012 22:32:45 +0100
> From: Enno Rey<erey at ernw.de>
> To: IPv6 Hackers Mailing List<ipv6hackers at lists.si6networks.com>
> Subject: Re: [ipv6hackers] Win7 - no managed flag, DHCP address
> 	released?!?
> Message-ID:<20121107213245.GD23609 at ernw.de>
> Content-Type: text/plain; charset=us-ascii
> Hi,
> I can confirm this. built a test lab with three (Cisco) routers emitting RAs and a DHCP server. one router emitting RAs with at times O, at times M flag set.
> "DHCP based" info (prefix in case of M flag, DNS server in case of O flag) got lost once RA from one of the routers emitting RAs_without_flags received. Win7 clients, (Cisco) default prefix/address lifetime (30/7 days).
> thanks
> Enno
> On Fri, Oct 19, 2012 at 12:33:28AM +1100, Karl Auer 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.
>> -- 
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> Karl Auer (kauer at biplane.com.au)
>> http://www.biplane.com.au/kauer
>> http://www.biplane.com.au/blog
>> 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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