Duplicate Address Detection misfire?

Zaphod Beeblebrox zbeeble at gmail.com
Mon Jul 22 05:22:36 UTC 2013


I've further narrowed this down.  According to the output:

em0 DAD detected duplicate IPv6 address fe80:2::250:56ff:fe2e:45fd: NS
in/out=2/1, NA in=0

... FreeBSD *thinks* it has transmitted one and received 2 solicitations.
The packet dump shows two solicitations (which would, if it were not bogus,
indicate that another machine was booting at the exact same time trying to
use the same link-local address).

The question becomes: is vmware duplicating the packet, or is FreeBSD?  IE:
driver problem with em0 and vmware?

I'm not completely sure how to debug this.



On Thu, Jul 18, 2013 at 9:21 PM, Zaphod Beeblebrox <zbeeble at gmail.com>wrote:

>
>
>
> On Sun, Jun 30, 2013 at 10:39 PM, Kevin Day <kevin at your.org> wrote:
>
>>
>> On Jun 30, 2013, at 6:48 PM, Zaphod Beeblebrox <zbeeble at gmail.com> wrote:
>>
>> > I have a FreeBSD 9.1-RELEASE vmware guest running. It is using the
>> > "bridged" type of networking with VMWare.  It gets it's IPv4 address
>> from
>> > DHCP (successfully) and then fails to initialize IPv6.  The relevant
>> > rc.conf is:
>> >
>> > ipv6_activate_all_interfaces="YES"
>> > ifconfig_em0_ipv6="inet6 accept_rtadv"
>> > ip6addrctl_verbose="YES"
>> >
>> > The console output says:
>> >
>> > em0: DAD detected duplicate IPv6 address fe80:2::20c:29ff:fe0a:3989: NS
>> > in/out=2/1, NA in=0
>> > em0: DAD complete for fe80:2::20c:29ff:fe0a:3989 - duplicate found
>> > em0: manual intervention required
>> > em0: possible hardware address duplication deteted, disable IPv6
>> >
>> > And subsequently, em0's nd6 has "IFDISABLED" in it.
>> >
>> > With wireshark, I see two ICMPv6 neighbor solicitations that are
>> identical
>> > --- is this the problem?
>> >
>> > How do I fix this?
>>
>> Did you copy this VM and have both copies running at once? If so, it
>> assigned the same MAC address to each VM.
>>
>> VMware is suppose to detect this and ask if you "copied" or "moved" the
>> VM, and if you say "copied" it will randomly assign a new MAC to the VM. If
>> this didn't happen or if you said "moved" when you actually copied it, just
>> go in and delete/re-create the network interface in the VM's settings to
>> create a new MAC for it.
>>
>> If that's not the issue, we'd probably need more details about your
>> configuration.
>>
>
> To further diagnose, there is only one VM running.  To ensure that there
> were no duplicates, I reassigned the MAC address in the VMWare
> configuration dialogue.  Additionally, I tried stopping rtadvd on my router
> (no effect) and I tried putting the guest on a "host-only network"
> (basically isolated it) --- this clears the problem --- both the link-local
> and the static address are assigned.
>
> Frustrated, I dumped the windows interface that is bridged to the VMWare
> guest.  When it boots, I see the following:
>
> 2461    19:24:16.376027000    Vmware_2e:46:fd    Broadcast    ARP    42
> Gratuitous ARP for 66.96.20.42 (Request)
> 2462    19:24:16.388241000    ::    ff02::1:ff00:42    ICMPv6    78
> Neighbor Solicitation for 2001:1928:1::42
> 2463    19:24:16.389065000    ::    ff02::1:ff00:42    ICMPv6    78
> Neighbor Solicitation for 2001:1928:1::42
> 2464    19:24:16.444130000    ::    ff02::16    ICMPv6    130    Multicast
> Listener Report Message v2
> 2465    19:24:16.444605000    ::    ff02::16    ICMPv6    130    Multicast
> Listener Report Message v2
> 2466    19:24:16.594663000    ::    ff02::1:ff2e:46fd    ICMPv6    78
> Neighbor Solicitation for fe80::250:56ff:fe2e:46fd
> 2467    19:24:16.595179000    ::    ff02::1:ff2e:46fd    ICMPv6    78
> Neighbor Solicitation for fe80::250:56ff:fe2e:46fd
> 2753    19:24:22.274728000    Vmware_2e:46:fd    Broadcast    ARP    42
> Who has 66.96.20.33?  Tell 66.96.20.42
> 2754    19:24:22.274902000    Intel_bc:6f:87    Vmware_2e:46:fd    ARP    60
> 66.96.20.33 is at 00:0e:0c:bc:6f:87
>
> ... and then it goes on to chatter ipv4-wise as expected.  Note that there
> are two of each packet.  Is that normal?  The ethernet source of all these
> packets is my vmware guest (save the who-has reply that I copied in).
>
>


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