Re: IPv6 and IP in parallel

On Tue, 2014-08-26 at 08:30 +0200, Harald Dunkel wrote:
Hi Thomas,

On 08/25/14 19:53, Thomas Haller wrote:

when you start NetworkManager...

..., and the interface has already some IP configuration, NM tries to
take over that configuration non-destructively (1). In that case, NM
looks for a matching connection and pretends that the connection is
already active on your device -- without actually changing the device.

If no matching connection can be found, it creates a connection. That
connection is in-memory only, until you delete it or until you
save/modify it. That was "eth0" you see, and it contains dhcp data,
because NM does not know that some parts came via DHCP6.

So it sees the IPv6 configuration on eth0 coming from somewhere,
doesn't find a connection configuration for it, takes eth0 as it
is and doesn't setup IPv4?

I think they come from:

        auto eth0
        iface eth0 inet dhcp
        iface eth0 inet6 auto

maybe dhcp4 is not yet complete when NM starts and NM thinks that IPv4
is disabled.

A solution might be to remove "auto eth0" if you want to use NM.

Do you think this could be improved?

generating a connection involves lots of guess work, and cannot always
work correctly. It should be improved as particular failure cases are

IMHU IPv4 and IPv6 are separate
protocols with different means for configuration and very little in
common. Shouldn't n-m use/create separate connections for these

A "connection" (in NM terms) is a configuration profile that you can
activate. Since NM generates *one* connection to match what it sees, the
connection has configuration for both IPv4 and IPv6.

You can avoid (1) by not configuring the interface externally.

Surely this "somewhere" is something I have to investigate. Stay tuned.

/etc/network/interfaces ?


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