"Link is down" in the kernel ring buffer

[myoshida]

Hello,

I am facing an EtherCAT communication failure. In our system, a Linux PC works as EtherCAT master.
I found the error messages as below in the kernel ring buffer obtained with the "dmesg" command.
ec_igb 0000:08:00.0 ec_eth0: igb: ec_eth0 NIC Link is Down (ec-patched)
To identify the cause of the failure, I would like to know exact meanings of the message.

Does anyone happen to know what the error message exact mean?
I assume it might represent link is down at either layer of OSI model. If my assumption is correct, could you tell me which layer?
I hope this is a general question and can be answered without kernel version or any further information. In case those information is needed, please let me know. (I have to go check.)

Thank you in advance for your kind help.

 

[osprey]

First I would check hardware connections.

 

[myoshida]

First I would check hardware connections.

Thank you very much for your reply.

I have checked hardware connections is ok including an EtherCAT cable between the PC (EtherCAT master) and the first slave. I am about to look into the first slave. If the error message in the ring buffer represents link is down only at Application Layer, the PC might be connected with the first slave at Physical Layer and Data Link Layer and can access EtherCAT slave hardware (ESC), which contains error codes. Unfortunately the current PC does not implement function to obtain error codes of the slaves. Therefore I am going to make it if it is worth doing.

 

[Brickwizard]

Cables can get damaged and if any dampness about cause corrosion tin the terminal plugs causing Dry joints,
If you are sure that the cables/connections are ok, take a look at this article [yes I know its a few years old but it may give you a guide]. https://serverfault.com/questions/585442/eth0-nic-link-is-down-repeating-message-in-kernel-log