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Yesterday I connected my Thinkpad's ethernet connection to a device which may have supplied PoE without me knowing. Also, it was a direct connection between my Laptop and the device (I manually set the IP address).

Now back to normal I figured that my ethernet connection is not working anymore, not via the docking-station, not via the direct port.

It seems the device is failing to establish the physical connection: no LEDs are blinking, neither on the switch-side nor on the laptop.

I tried using ethtool to reset all (not supported), disable/enable auto-negotiation, setting mdix to auto, on, off. ethtool -t's self-test shows

The test result is FAIL
The test extra info:
Register test  (offline)     0
Eeprom test    (offline)     0
Interrupt test (offline)     0
Loopback test  (offline)     0
Link test   (on/offline)     1

I even booted to Windows to see whether it works there, no it doesn't. The Lenovo self-test tool does not even show the ethernet adapter, the device manager does and says everything is OK.

The device is: 

*-network
     description: Ethernet interface
     product: Ethernet Connection (4) I219-V
     vendor: Intel Corporation
     physical id: 1f.6
     bus info: pci@0000:00:1f.6
     logical name: enp0s31f6
     version: 21
     serial: 8c:16:45:33:42:ea
     capacity: 1Gbit/s
     width: 32 bits
     clock: 33MHz
     capabilities: pm msi bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
     configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=3.2.6-k firmware=0.1-4 latency=0 link=no multicast=yes port=twisted pair
     resources: irq:144 memory:dc200000-dc21ffff

on a Thinkpad T480s. (see that it says link: no, but it is actually connected to the switch).

Is there anything additional I can try on the software side before sending the device to LENOVO for repair?

mael'
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Patrick B.
  • 3,128

1 Answers1

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Looking at other answers on Super user, PoE should not send any power until the device has asked for it. So it is unlikely that is the case.

I would suggest to try another cable, try the cable on another device and try other ports on the router/switch.

Other than that, it is hard to diagnose a hardware fault like that.

EDIT: A bit mroe research and it appears that if you have passive PoE, you can indeed damage ethernet ports. I would still suggest you test the cable with another device if you can, just to be sure. Otherwise, you might have caused some damage.

Randomhero
  • 1,543