windows 7 dhcp stateful config ipv6

[tslbai]

Dear List-members,

in my network, the ipv6-addressing of a win7-Client by dhcp fails. Would
you pleas give me a hint, where's my mistake?

I'm runnig a small network with a cisco-router, a centos 6.4 server and
an win7 (actual patchlevel) client.
On the centos i installed the latest version of isc-dhcp 4.2.5-P1.
Here's my Config:

--------------------
authoritative;
log-facility local4;
default-lease-time 600;
max-lease-time 7200;

subnet6 2001:a60:900f::/64 {
        preferred-lifetime 360;
        option dhcp6.name-servers 2001:a60:900f::2;
        option dhcp6.domain-search  "agilolfinger.de";
}

host tasssilo {
  hardware ethernet 00:17:31:d1:6d:ae;
  fixed-address6 2001:a60:900f::a0a2;
}

i also tried:
-----------------------
host tasssilo {
  host-identifier option dhcp6.client-id
00:01:00:01:19:55:9B:9C:00:17:31:D1:6D:AE;
  fixed-address6 2001:a60:900f::a0a2;
}

The "dhcp6.client-id" i took from my Windows ipconfig /all:
"DHCPv6-Client-DUID".


----------------------
The dhcp-server is starting
/usr/local/dhcp425p1/sbin/dhcpd -6 -cf /etc/dhcp/dhcpd6min.conf
without errors an says:
...
Listening on Socket/5/eth0/2001:a60:900f::/64
Sending on   Socket/5/eth0/2001:a60:900f::/64

In my ip6tables i allowed icmpv6:
-A INPUT -p icmpv6 -j ACCEPT
-A OUTPUT -p icmpv6 -j ACCEPT

-----------------------------
The Windows 7 Client is configured as describeb here:
http://support.microsoft.com/kb/961433/EN-US

netsh interface ipv6 set int 13 advertise=enable managed=enable
routerdiscovery=disabled

-----------------------------
On the Cisco-Side the managed- and other-flag are set in the interface
 ipv6 nd managed-config-flag
 ipv6 nd other-config-flag
Btw.: I Think, this doesn't matter here, because Win7 is not able to
read these flags in a router-solicitation.

-----------------------------
Now the Problem:

When i run
ipconfig /renew6
on Windows, nothing happens.

I can see with wireshark, that the Windows-Client is sending from his
ll-address many icmpv6-messages (DHCPV6) to the multicast ff02::1:2 (all
dhcp relays & servers), but the isc-server in the same network is not
responding.
There's no log-entry or anything else, but you can see the
request-packets arriving on the server (by tcpdump).


Would you please give me a hint, what to do?


Thanks,

Florian