Reestablish network connection after the ETH cable replugged in

[hikaru2001]

Hello guys,

After I plug out the ethernet cable from RevPi Core3 and plug it in again. The ethernet connection won't be reestablished. My laptop can't ping RevPi Core 3 again until I power on RevPi Core 3 again.
Is that normal? How can I do some settings in order to make RevPi Core3 restart ethernet connection automatically?
Thank you so much!

[dirk]

Hello hikaru2001, I need more information. Can you send me a sos report?

Code: Select all

sudo apt update
sudo apt install revpi-tools
revpi-sos

It works like so:

Code: Select all

pi@RevPi40302:~ $ revpi-sos
The report will be generated under folder /tmp in a .tar.xz file, which
can be extracted with command: tar -Jxvf xxx.tar.xz in linux or 7zip in Windows.
And then some inspection can be done before it is sent to support@kunbus.com.
Are you going to continue (N/y)?y
report generating...

Your report has been generated and saved in:
/tmp/sosreport-RevPi40302-20201102163308.tar.xz

To make the report have better accessibility, the ownership of the report
can be changed to the current user.
Are you going to proceed(N/y)?y
The ownership of /tmp/sosreport-RevPi40302-20201102163308.tar.xz has been changed to user:pi

Please have in mind that you agree to send us private data i.e. IP address.

Send the report to support@kunbus.com

[hikaru2001]

Hi Dirk,

I have sent you the SOS report by email.
Today I try "sudo ip link set eth0 down && sudo ip link set eth0 up" and find that the connection-reestablish problem can be solved. The network connection will be rebuilt whenever the ethernet cable is plugged out and in again after that command is executed.

[dirk]

Hi, we have received the sos-report with thanks, discussed it in the RevPi Stand Up and roughly analyzed it:
We noticed the following things in the Kern.log shortly before the eth0 connection is restarted:
There are messages from the USB power management: "eth0: hardware isn't capable of remote wakeup".
One or more Logitech USB HID devices report "HID++ 2.0 device connected".
These are only rough hits but can be a good start for troubleshooting.

The command you describe and the solution is not quite clear to us.
Is it enough to enter the command only once after a connection loss and then not anymore?
Or every time the connection is lost.

[hikaru2001]

Hi Dirk,

The command is only entered once, then the connection will always recover automatically after the cable is plugged out and in again.

[dirk]

Hi hikaru2001, this is interesting that you have to enter the command only once.

Is the command entered on the RevPi or on the laptop? So you need a HDMI and a USB Keyboard as you don't have SSH access to the RevPi.
Call ethtool if there is no more link and see if a physical link is displayed?
We have to reproduce the error so that we can understand what caused it.

[hikaru2001]

Hi Dirk,

Sure the command is entered on RevPi!
After the error is reproduced, I call ethtool and the result is "Link deteted: yes", "Auto-negotiation: on".

[dirk]

Hi hikaru2001, please try the following:

• Power cycle the RevPi
• start a Wireshark capture on your Laptop
• run the command on your RevPi "sudo tcpdump -i eth0 -C /tmp/capture.pcap"
• pull the Ehternet cable and plug it again after a few seconds
• ping the RevPi from your laptop - it should not be possible
• stop and save the Wireshark capture on the laptop
• cancel the tcpdump on the RevPi
• run the command on your RevPi "ethtool -S eth0" to give out the error couters and other statistics and make a screenshot.

Send us everything.

Hopefully we'll see things clear then. Thank you for your work.

[dirk]

Hi hikaru2001, do you have updates for me? Is this issue still open?

[hikaru2001]

Hi Dirk,

Sorry for my late reply! On some day of the second last week, the reestablish network connection problem didn't exist while I hadn't done anything to RevPi Core3. I want to simulate the error again for a long time, but not realized.
Maybe the issue can be closed. Thank you!