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I am running Ubuntu 18.04.4 server on a system that I have attached to it a Realtek 8156 2.5 Gbps ethernet USB adapter. While this adapter otherwise works when attached to a USB 3 port, my syslog is full of lines that look like this:

Apr 16 06:25:06 master kernel: [193945.748989] cdc_ncm 2-2:2.0 usbeth0: 2500 mbit/s downlink 2500 mbit/s uplink
Apr 16 06:25:06 master kernel: [193945.780987] cdc_ncm 2-2:2.0 usbeth0: network connection: connected

These lines get emitted every 30 ms or so. This makes my syslog rather unusable.When I detached the USB adapter, the log lines stop, but I do want this adapter attached, so that's not a workable solution.

How can I get these log lines to stop?

kamprath
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  • Maybe look into disabling the USB AutoSuspend. I have forever seen issues with USB Networking devices on systems not being stable due to power saving. https://askubuntu.com/questions/185274/how-can-i-disable-usb-autosuspend-for-a-specific-device That answer for 16.04 can still be used for 18.04 – Terrance Apr 18 '20 at 04:07
  • @Terrance Thanks for the idea, but unfortunately, that did not work. Still getting the spam in the syslog. – kamprath Apr 18 '20 at 04:44
  • I guess try disabling power saving modes on the system. I have been looking all over the internet about USB ethernet adapters and they all are basically about the same consensus about power saving being the culprit for adapters disconnecting and reconnecting. Yours just happens to be doing it at a much quicker rate that isn't noticeable. In my opinion, this is the reason why I stopped using USB ethernet / wifi adapters. – Terrance Apr 19 '20 at 15:09
  • The USB device is not going through power savings cycles. The setting in /sys/bus/usb/devices/***/power/control is on, which according to https://hamwaves.com/usb.autosuspend/en/index.html means it should not be autosuspending. – kamprath Apr 19 '20 at 19:13
  • No, it shouldn't be, but that is the only reason why it keeps showing that it is connected over and over again because it is cycling. Check in your system BIOS and disable anything for power saving. If that doesn't change it, maybe the device itself is bad. I agree that it should not be spamming your logs with that. – Terrance Apr 19 '20 at 20:18

1 Answers1

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So it turns out that in Ubunutu 18.04 the built in driver support for the Realtek 8156 chip is not complete. The solution to my problem ended up being manually compiling and installing the device drivers from RealTek. The Linux driver can be downloaded here. The driver does need to get built, so you need to install the build-essential package via apt. The driver download's README has information on how to instal the kernel module once it's built. Once I installed this driver, all the spammed messages in syslog went away (yay!).

kamprath
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  • Hi, I am having the same issue. I followed the guide and the README, and the module is successfully inserted into the kernel, but I still get messages spammed in my syslog. Since installing the uplink/downlink has changed from 2500 mbit/s to 1000 mbit/s, but nothing else has changed. – tigerninjaman Jun 15 '21 at 08:08