macos Sierra with CGA address?

Jeroen Massar jeroen at
Wed Dec 14 13:10:42 CET 2016

> Actually, it is not a stable address as some have found out (read:
> anecdotal), they also change at re-install and there are a couple of
> other possibilities from what I recall.

>From xnu-3248.60.10/bsd/netinet6/in6_ifattach.c:

 * Generate a last-resort interface identifier, when the machine has no
 * IEEE802/EUI64 address sources.
 * The goal here is to get an interface identifier that is
 * (1) random enough and (2) does not change across reboot.
 * We currently use SHA1(hostname) for it.
 * in6 - upper 64bits are preserved

So good luck when you get a hostname over DHCP :)

There are some other comments there that could be enlightening, but this
code definitely does not match the released code, it is running behind
quite a bit.


More information about the ipv6-ops mailing list