[SOLVED] Unstable LAN wired connection

Kernels & Hardware, configuring network, installing services

[SOLVED] Unstable LAN wired connection

Postby andoru » 2018-04-12 19:55

I previously asked for assistance here:
https://reddit.com/r/linuxquestions/com ... onnection/

I seem to have some problems getting a second-hand machine (HP Elite 8200) to properly connect. The connection is very unstable, many times not being able to load any pages in the browser, getting pings over 200ms, and getting many 408 HTTP errors.

I've checked Debian and Linux Mint so far, and both have this issue. I also wanted to try booting into a live session of both System Rescue CD and Gentoo as per the suggestions of the commenters in that reddit post, but I was unable to make the PC boot into those two either from grml-rescue nor from a pendrive.

I've checked the ethernet port in the back of the machine, and it is intact, the cable isn't damaged as I've tried it with another machine, and it works as expected.
Also there are no signs that the motherboard and it's components are damaged (bloated capacitors, stains, blown chips, corroded traces, etc)

What I currently assume to be the culprit: the network interface on the machine is broken/dead in a way that's not obvious. Or there's something misconfigured somewhere (either router, BIOS or in the OS), or the driver for the network interface (which is an Intel 82579LM) is buggy.

Now I know that the former cannot be fixed without replacing the whole machine or getting a network card, but could someone suggest what I could try to diagnose software-wise, in case it's the latter case?

Thank you in advance!

EDIT: tl;dr - The culprit was the cable. It's not damaged, and I can connect other devices to it and it works, but this particular NIC doesn't really like it. I'll be changing the cable with a CAT6 one and hopefully I won't have this issue.

EDIT2: Changed the old cable with a Cat 6a S/FTP one, and now the NIC works properly.
Last edited by andoru on 2018-04-21 15:34, edited 4 times in total.
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Re: Unstable LAN wired connection

Postby Dai_trying » 2018-04-12 20:20

If you could install inxi and post the output of inxi -n it might help diagnose your problem.

Also I noticed you mentioned something about gigabit connection in the reddit post which makes me think you might need the tg3 firmware which I believe is in the package firmware-misc-nonfree
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Re: Unstable LAN wired connection

Postby andoru » 2018-04-12 20:30

Alright, will install inxi and post the output.

The network interface is gigabit capable, but the connection itself is only 100mbps.
I'm a bit queasy about installing nonfree stuff, but I'll try it and see if it improves anything. Thank you!

EDIT: Love your username!
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Re: Unstable LAN wired connection

Postby Segfault » 2018-04-12 21:21

In cases like this I usually reach for my trusty 2 GB USB stick with latest SystemRescueCD on it. Just to test if issue is with installed Linux or hardware.
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Re: Unstable LAN wired connection

Postby andoru » 2018-04-12 21:24

As I previously mentioned, I tried booting System Rescue CD from within gldr-rescue, and since that didn't work, I then wrote it to a USB pendrive, but the machine just won't boot it...
I was lucky enough that both the Debian netinstall iso, and Linux Mint's iso work with this machine. I have no idea why the others don't budge...

EDIT: I cannot grammar.
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Re: Unstable LAN wired connection

Postby Dai_trying » 2018-04-12 21:58

andoru wrote:I'm a bit queasy about installing nonfree stuff, but I'll try it and see if it improves anything. Thank you!

It's one of those things with firmware, you sometimes need the non-free firmware to be able to use some hardware properly, but you can always disable the non-free repository once you have the required firmware (if it is actually needed which hopefully we will find out), and you're welcome.

andoru wrote:EDIT: Love your username!

Thanks, Me too :D
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Re: Unstable LAN wired connection

Postby andoru » 2018-04-13 01:55

Dai_trying wrote:If you could install inxi and post the output of inxi -n it might help diagnose your problem.

Also I noticed you mentioned something about gigabit connection in the reddit post which makes me think you might need the tg3 firmware which I believe is in the package firmware-misc-nonfree


Haven't got the chance to try installing the firmware, but here's the inxi output:

Code: Select all
$ inxi -n
Network:   Card: Intel 82579LM Gigabit Network Connection driver: e1000e
           IF: eno1 state: up speed: 100 Mbps duplex: full
           mac: --:--:--:--:--:--


Segfault wrote:http://www.system-rescue-cd.org/Installing-SystemRescueCd-on-a-USB-stick/


Ah, didn't see that earlier.
The isohybrid method did not work for some reason, but mouting the ISO and running the script from the root path of the image produced a bootable pendrive.
However sadly, the connection is unstable in SystemRescueCD too...
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Re: Unstable LAN wired connection

Postby Dai_trying » 2018-04-13 04:13

andoru wrote:
Code: Select all
$ inxi -n
Network:   Card: Intel 82579LM Gigabit Network Connection driver: e1000e
           IF: eno1 state: up speed: 100 Mbps duplex: full
           mac: --:--:--:--:--:--



That appears to be using the correct driver/firmware so I cannot offer much more help I'm afraid, what I would try though is a live-Cd of a distro based on Buster to see if it happens with the testing version or if it might have updated versions which fix your issue. Sorry I couldn't help more but I hope you find a fix.
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Re: Unstable LAN wired connection

Postby Segfault » 2018-04-13 09:51

The MAC address is not showing, there is something broken in hardware or BIOS/firmware.
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Re: Unstable LAN wired connection

Postby Dai_trying » 2018-04-13 10:24

Segfault wrote:The MAC address is not showing, there is something broken in hardware or BIOS/firmware.

I must admit I thought OP removed it for privacy reasons but I agree it could be an issue. It might be worth getting the latest firmware from the Intel site to see if that works better...
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Re: Unstable LAN wired connection

Postby Segfault » 2018-04-13 11:29

There cannot be any privacy issues with ethernet MAC address, it is a Layer 2 attribute, it is used only on LAN.
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Re: Unstable LAN wired connection

Postby p.H » 2018-04-13 13:12

Dai_trying wrote:Also I noticed you mentioned something about gigabit connection in the reddit post which makes me think you might need the tg3 firmware which I believe is in the package firmware-misc-nonfree

andoru wrote:Network: Card: Intel 82579LM Gigabit Network Connection driver: e1000e
IF: eno1 state: up speed: 100 Mbps duplex: full
mac: --:--:--:--:--:--

Err, I seriously doubt that this Intel NIC needs any tg3 (Broadcom) firmware.
Is it the output "as is" or did you hide the MAC address ? Please don't, or at least leave the first 3 bytes (manufacturer's OUI) untouched.
Dai_trying wrote:you can always disable the non-free repository once you have the required firmware

Why would you want to do this ? What about security updates ?
Segfault wrote:There cannot be any privacy issues with ethernet MAC address, it is a Layer 2 attribute, it is used only on LAN.

You're wrong. MAC addresses can appear in autoconfigured global (ie public and routable) IPv6 addresses.

By the way, has anyone suggested to check related messages in the kernel logs ?
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Re: Unstable LAN wired connection

Postby Segfault » 2018-04-13 13:46

You saying the MAC address of my NIC will be seen after umpteen hops on the internet when using IPv6?

BTW, PCI ID is much better identifier when in comes to hardware identification. By PCI ID you can grep the kernel sources or search the kernel driver database at cateee.net.

Example:
Code: Select all
00:1f.6 Ethernet controller [0200]: Intel Corporation Ethernet Connection (2) I219-V [8086:15b8] (rev 31)


Heading over to cateee.net I can see the driver for my NIC 8086:15b8 has been in the kernel since kernel version 4.1.
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Re: Unstable LAN wired connection

Postby p.H » 2018-04-13 14:28

Segfault wrote:You saying the MAC address of my NIC will be seen after umpteen hops on the internet when using IPv6?

Yes, it may, depending on how the global IPv6 address assigned to the interface is generated.

Segfault wrote:BTW, PCI ID is much better identifier when in comes to hardware identification.

MAC address and PCI ID do not have the same purpose at all.
PCI ID is more like a part number.
MAC address is more like a serial number.
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