Ubuntu 16.04

[Tore Anderson]

* Mikael Abrahamsson

> I have a pretty standard Ubuntu 14.04 machine I just upgraded to 16.04, 
> which means I get a "4.4.0-21-generic" kernel.
> 
> I guess I'm using straight up network manager, because my 
> /etc/network/interfaces doesn't mention anything about eth0 or wlan0, only 
> lo.
> 
> In the GUI, it came default with "privacy extensions disabled".

Ubuntu (at least previous versions) hard-codes privacy extensions to be
on and preferred, overriding any user configuration to the contrary in
NM or /etc/network/interfaces. You need to
delete /etc/sysctl.d/10-ipv6-privacy.conf for your NM/interfaces
setting to take effect.

https://bugs.launchpad.net/bugs/1497166

> I used to administrate this device using its EUI64 based SLAAC
> address, which was stable across reboots. Now with 16.04, I get two
> addresses, none of them stable across reboots.
> 
> Anyone know what the thought is behind this? I want to continue using 
> SLAAC and I'm fine with privacy extension addresses over time, but I
> want a single stable address across reboots.

Are you 100% sure one of the addresses isn't stable? NM-1.2 defaults to
using RFC7217 IID instead of EUI-64, and I believe Ubuntu 16.04 ships
with a NM-1.2 or (or a release candidate).

https://blogs.gnome.org/lkundrak/2015/12/03/networkmanager-and-privacy-in-the-ipv6-internet/

(This is orthogonal from the use of RFC4941 privacy addresses, btw.)

However RFC7217 IIDs are supposed to be stable across reboots, and on
my Fedora 23 system, they are. If they aren't with you, maybe something
goes wrong with storing the stable secret key? On my system, it's
stored in /var/lib/NetworkManager/secret_key, for what it's worth.

What does "nmcli con show <yourconnamehere> | grep ipv6" say?

Tore