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Princess Nell
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PostPosted: Tue Aug 25, 2020 10:02 am    Post subject: A difference of opinion Reply with quote

Problem: ethernet connection works at home, but not in the office. NM will not establish a connection, but I think this is only a symptom, NM is not the problem. Not sure when this started, could have been kernel 5.x, or a switch upgrade in the office.

This is a ThinkPad X260 with
Code:

00:1f:6 Ethernet Controller: Intel Corporation Ethernet Connection I219-LM (rev 21)

The driver is e1000e.

Observation 1: upon "ifconfig eth0 down", both lights on the NIC come on, and the switch port it is connected to says "<port> is up, line protocol is up (connected)".

Observation 2: upon "ifconfig eth0 up", both lights go off, and the switch says "<port> is down, line protocol is down (notconnect)".

This is kind of the other way round from what I expect.

Workaround: stop NM, manually set IP and route. Literally, "ifconfig eth0 <IP> netmask 255.255.255.0", brings up the interface and all is good on the switch, too.

Am I looking at dodgy hw? Funny driver behaviour? Any insights would be appreciated.
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Banana
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PostPosted: Tue Aug 25, 2020 12:49 pm    Post subject: Reply with quote

so the main difference is a different cable? Does work use a different network config? If so, how do you switch?
Do you shut down your device or just suspend, reconnect and expect it to work?
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Princess Nell
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PostPosted: Tue Aug 25, 2020 9:29 pm    Post subject: Reply with quote

I turn the device on and expect it work ;)

I might test a different cable. Don't think it's a factor since everything works when I configure the interface manually. Wireless also works fine and as expected, so I'm assuming the underlying network is sound, as is the dhcp server.

Yes, a different network config works (different vlan), and that involves a different cable, but also a different access switch.
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Banana
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PostPosted: Wed Aug 26, 2020 8:32 am    Post subject: Reply with quote

So no hibernate and stuff? Since this is often a source of problems with network connections.

Switching a network with different settings just b unplugging the cable should only work if you restart your connection settings. Otherwise the connection will use the current loaded one which my be not the required settings fpr the new network you are trying to connect to.
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coderanger
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PostPosted: Wed Aug 26, 2020 8:34 am    Post subject: Re: A difference of opinion Reply with quote

Princess Nell wrote:
Observation 1: upon "ifconfig eth0 down", both lights on the NIC come on, and the switch port it is connected to says "<port> is up, line protocol is up (connected)".
Observation 2: upon "ifconfig eth0 up", both lights go off, and the switch says "<port> is down, line protocol is down (notconnect)".
I have similar network card (I219-V [8086:15d6]) but I have never observed such behavior with ifconfig up/down. This is really weird for a single network card installed on a laptop. With 2 network cards the name eth0 can be assigned randomly, when you bring down one card then something like BIOS or networkmanager starts another. Need to make sure eth0 is the right interface, it can be identified with ethtool, the yellow led will start blinking constantly:
Code:
ethtool -p eth0 120
Princess Nell wrote:
Workaround: stop NM, manually set IP and route. Literally, "ifconfig eth0 <IP> netmask 255.255.255.0", brings up the interface and all is good on the switch, too.
Maybe, a badly crimped cable. ifconfig forces some low level settings and it starts working. Or the guy who crimped connectors did not follow color palette. Test with different cable/patchcord (you can ask IT department), visually check that the color palette on connectors is crimped properly, ask them to connect you to different port in the box where their switch is installed.
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Princess Nell
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PostPosted: Fri Aug 28, 2020 11:26 am    Post subject: Reply with quote

Different cable, different port, same problem.

This did coincide with the installation of a new access switch in the office. And no other box has this problem. I've been setting up several laptops with a well-known Enterprise distribution, all ThinkPads (but other models), and they all work fine.
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CaptainBlood
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PostPosted: Fri Aug 28, 2020 5:44 pm    Post subject: Reply with quote

Just my 2c:
Can you test alternate working computer from the company on the very same net plug that fails?
Could it be IPV6 issue?
Thls 4 ur attention, interest, & support.
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Princess Nell
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PostPosted: Mon Aug 31, 2020 10:18 pm    Post subject: Reply with quote

Yes, I have tried other ThinkPads with CentOS 7/8 on the same cable/port, and they all work.

I think I'll mothball that gentoo setup altogether and switch fully to CentOS in the office. There are things that I just can't get to work in a satisfactory manner, and they're fine on CentOS. This is the general area of "firefox+sound", and my refusal of switching to PA (no choice but to accept it on CentOS).
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