Comment 1 for bug 1541544

------- Comment From <email address hidden> 2016-02-04 02:52 EDT-------
HI,

(In reply to comment #0)
> When I configure a qeth OSA device, the installer asks for device type,
> device and protocol layer:
>
> Please choose the type of your primary network interface that you will need
> for
>
> installing the Debian system (via NFS or HTTP). Only the listed devices are
>
> supported.
> Network device type:
> 1: ctc: Channel to Channel (CTC) or ESCON connection,
> 2: qeth: OSA-Express in QDIO mode / HiperSockets,
> 3: iucv: Inter-User Communication Vehicle - available for VM guests only,
>
>
> 4: virtio: KVM VirtIO,
> Prompt: '?' for help> 2
> 2
>
> Please select the OSA-Express QDIO / HiperSockets device.
> Device:
> 1: 0.0.f5f0-0.0.f5f1-0.0.f5f2 [*],
> Prompt: '?' for help, default=1> 1
> 1
>
> By default OSA-Express cards use layer3 mode. In that mode LLC headers are
> removed from incoming IPv4 packets. Using the card in layer2 mode will make
> it
> keep the MAC addresses of IPv4 packets.
> Use this device in layer2 mode?
> 1: Yes [*] 2: No
> Prompt: '?' for help, default=1>
>
> The last question experienced a change according to
> https://bugs.launchpad.net/ubuntu/+source/s390-netdevice/+bug/1526801
> Layer2 is the default, which is correct, since the qeth driver uses layer2
> as default as well.
>

I wonder why the default has been changed at all. The default is just a guess. The s390-netdevice does not have any heuristics to determine a potential correct default and I would have to investigate if that is possible.

The system administrator should provide information about whether layer2 or layer2 is used for a particular network interface. Statement like "By default OSA-Express cards" are incorrect as the modes can be configured. The same applies for HiperSocket devices. And also there is real and virtual OSA/HiperSockets.

One last note, if you misconfigure the layer2 setting you want get a network connection.