Re: IPv6 duplicate address detection (DAD)
Darac Marjal <mailinglist@darac.org.uk> wrote:
> On Wed, Mar 25, 2015 at 01:49:31AM +0000, Michael Graham wrote:
>> I've been trying to understand what I should do about my current IPv6
>> wows.
>>
>> I have an IPv6 enabled network but when on a clean boot I don't get an
>> IPv6 address (in Jessie BTW), I've tracked this down to this message in
>> dmeg:
>>
>> IPv6: wlan0: IPv6 duplicate address fe80::fef8:aeff:fe7b:115f detected!
> This is the link-local address for the device with a MAC address of
> FC:F8:AE:xx:xx:7B:11:5F (where xx:xx is obscured by the IP address).
MAC addresses are only 6 bytes big. The FF:FE is merely inserted into the
middle and the 1st bit of the first byte of the MAC is flipped to
generate the host part of the IPv6 address.
> So, perhaps the DAD is correct and there is another device on your
> network trying for the same address (note that the address space of
> autoconfigured link-local addresses is smaller than that of MAC
> addresses - due to the FF:FE in the middle - so there IS a slim chance
> of a valid collision).
No, there is not chance of a collision. If DAD thinks there is another
device with the same address (and hence MAC) then there _is_ another
device with the same address or another anomaly (network loop, like you
already wrote).
Using a sniffer to clearly see, what is going on would also be my next
step in diagnosing this.
Grüße,
Sven.
--
Sigmentation fault. Core dumped.
Reply to: