macos Sierra with CGA address?

Matthew Ford ford at
Wed Dec 14 12:23:50 CET 2016

> On 14 Dec 2016, at 10:55, Holger Zuleger <Holger.Zuleger at> wrote:
> Hi,
> I just realized that the permanent interface identifier of my MAC has
> changed after upgrading to OS 10.12 (I guess).
> The output of ifconfig shows a new "secured" flag at the permanent address.
> $ ifconfig en0 | grep inet6 | \
>>      sed "s/2[^:]*:[^:]*:[^:]*:[^:]*:/<prfx48>:/"
> inet6 fe80::c54:6333:ac12:c67b%en0 prefixlen 64 secured scopeid 0x4
> inet6 <prfx48>:20e3:84f6:6794:5ace prefixlen 64 autoconf secured
> inet6 <prfx48>:8822:a8a3:b6ec:a79b prefixlen 64 autoconf temporary
> I found two or three posts in the internet, all mentioning (or hoping)
> that this is related to a change to RFC7217 as default IID mechanism.
> But one guy sad, that the source code (of 10.11) shows, that this is a
> cryptographic generated interface identifier for SeND (RFC3971).
> I tend to believe that the latter is true.
> Has anyone more information about this? Especially how to configure it?

man ifconfig says:

" insecure
             Disable the processing of Secure Neighbor Discovery (SEND).

             Do not disabled the processing of Secure Neighbor Discovery


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