Re: Strange cabled network fault when rebooting from Windows (any version) into Ubuntu 24

Java Jive <[email protected]> wrote:

> On 2025-11-15 16:17, vallor wrote:
>> At Sat, 15 Nov 2025 15:17:26 +0000, Java Jive <[email protected]>
>> wrote:
>> 
>>> On 2025-11-15 15:04, Andy Burns wrote:
>>>> Java Jive wrote:
>>>>
>>>>> It seems to me from this that the cabled network hardware is not
>>>>> being properly initialised when booting Ubuntu 24.  The cure is
>>>>> simply to actually power down the PC before launching Ubuntu 24
>>>>
>>>> I had some older Dells (Precision and Dimension) which disabled the
>>>> NIC if it wasn't physically connected at the time it booted
>>>> Windows, there was a utility to re-enable it, probably doesn't
>>>> exist for Linux (though Dell were pretty good with their Linux
>>>> support via Fedora last time I kept up with it).
>>>
>>> Interesting piece of info ...  However, during the testing these were
>>> in E-Dock stations  -  from which they are only undocked when I
>>> travel, so weren't undocked during testing  -  so seemingly there
>>> wouldn't be any reason for either OS to disable the netcard, as it
>>> was permanently connected during the testing.
>> 
>> Weird problem.  If you want to troubleshoot, you might get
>> it into failure mode, then run ethtool on the ethernet device
>> to see if auto-negotiation is happening properly, if the
>> Linux driver thinks link is detected, and so forth.
>> 
>> What chipset does your Ethernet use, and is it part
>> of the dock?  It appears that Intel driver modules
>> have a "debug" option that can be set, not sure if
>> that helps...
> 
> Thanks for the suggestions, but now I know what causes it and the simple 
> fix, probably I shall just try to remember always to shut down the PC 
> before going into Ubuntu.
> 
> Back now in Windows, the cabled net card is described as 'Intel Ethernet 
> Connection I217-LM', and this doesn't change when docking and undocking 
> the PC.  Similarly, another PC's net card, again regardless of whether 
> it is docked or not, is described as 'Intel 82579LM Gigabit Network 
> Connection' (I haven't tested the Ubuntu 24 problem on that one, as it 
> wasn't the PC I noticed the problem on).  Given this, I think the dock 
> is merely an alternative connection between the PC's network interface 
> and the outside world, and doesn't have it's own separate network 
> interface in the dock itself.

Were doing a cold or warm reboot between switching OSes?  A cold reboot
has the CPU send a reset signal to all hardware to ensure the hardware
is at a known starting state.  A warm boot doesn't.  For a cold reboot,
(power cycle) the keyboard's LEDs should flash letting you know it got
the reset.

I've had DSP modem card (dial-up) that would get hung, and a warm reboot
aka restart wouldn't cure it, but a cold boot with its reset got the
modem back into a known and usable state, so the drivers could then
communicate to the modem.