Gentoo turns off ethernet link ligth during late boot

sigra · Tux's lil' helper Joined: 03 Feb 2006 Posts: 137

Trying to switch to a new Internet connection. When the Gentoo laptop boots with the Ethernet cable of the new Internet connection, the link light at the laptop's Ethernet port is on. But during late boot (something after the kernel), it is turned off. If the cable is inserted when the system is already fully booted, no light is turned on.

When the cable of the old Internet connection is connected, there is light and everything works.

When the cable of the new Internet connection is connected to a borrowed laptop, there is light and everything works.

Why is the link light turned off during late boot? I use dhcpcd because it is easiest.

bunder · Bodhisattva Joined: 10 Apr 2004 Posts: 5937

could this be a 100mbit vs 1gbps thing?

sigra · Tux's lil' helper Joined: 03 Feb 2006 Posts: 137

I rebuilt the kernel with QCOM_EMAC as a Yes instead of a Module and installed it. After boot it still turns off the link light.

Jaglover · Posted: Fri Dec 29, 2017 4:01 pm Post subject:

What ethtool tells about status of the connection?
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sigra · Tux's lil' helper Joined: 03 Feb 2006 Posts: 137

Jaglover · Posted: Fri Dec 29, 2017 4:30 pm Post subject:

sigra · Tux's lil' helper Joined: 03 Feb 2006 Posts: 137

Unlikely that the cable breaks at the same time every boot of the Gentoo laptop while it works with the borrowed laptop.

Jaglover · Posted: Fri Dec 29, 2017 4:50 pm Post subject:

But then again it works with old connection, something must be different with new connection because it cannot sense the physical connection. You could compare with ethtool output with working connection, maybe there is some clue.
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sigra · Tux's lil' helper Joined: 03 Feb 2006 Posts: 137

Jaglover · Posted: Fri Dec 29, 2017 4:58 pm Post subject:

OK, it runs at 100 Mbit/s with old connection. Does the borrowed laptop show 100 Mbit/s also with new connection?
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sigra · Tux's lil' helper Joined: 03 Feb 2006 Posts: 137

There is no ethtool on the borrowed laptop, but I tested with www.bredbandskollen.se and it reported 118,20 Mbit/s download and 17,42 Mbit/s upload. So the Ethernet link must be more than 100 Mbit/s.

Jaglover · Posted: Fri Dec 29, 2017 6:01 pm Post subject:

It is Gbit connection then. Here's what we know. Gentoo laptop works with 100 Mbit/s connection, but does not sense Gbit connection. What you make out of that. Bad laptop ethernet port, dirty or damaged connector pins? Have you tried to force 100 Mbit/s connection with new internet?
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1clue · Advocate Joined: 05 Feb 2006 Posts: 2569

Probably a nothing point, but gigabit ethernet is full duplex only. Your supported modes says half duplex, which is not a standard ethernet mode. Maybe one nic is insisting on gigabit/half and the other side rejects it?

So where is the cable change?

Do you have 2 separate routers/switches, two cables going to your laptop and then switch cables at the laptop port?
Do you have 1 cable going to 2 separate switches/routers, switching the same cable between devices at the end opposite of Gentoo?
Do you have a consistent connection from Gentoo to switch/router, and some other cable swap upstream?

What I'm getting at is this could be a bad cable or a bad port on a remote device.

sigra · Tux's lil' helper Joined: 03 Feb 2006 Posts: 137

I have 1 cable, 102 meter, now covered by a lot of snow, frozen soil and a public road. Thankfully, it works. I even tried to put the router of the old Internet connection at one end and the Gentoo laptop at the other end. It worked. So it seems that the Gentoo laptop does not work with the router/switch of the new Internet connection.

I just succeeded to get an old discontinued dovado router connected to the new Internet connection after upgrading it to the final firmware version. The Gentoo laptop can connect to it, so I can use it with the new Internet connection. So I can now terminate the old Internet connection.

I suppose that it works because the old dovado can only do 100 Mbit/s. When I get a new router I may have to find out how to force the Gentoo laptop to not try 1 Gbit/s, which does not work for some reason.

Thans for all the help so far.

1clue · Advocate Joined: 05 Feb 2006 Posts: 2569

OK can you tell me what cable spec your 102m cable is? Cat5? Cat5e? Cables have maximum throughput, and while it may not make much difference with a 2m cable it will certainly matter for 100m cable.

Have you actually tested that cable at gigabit speeds with a device at the other end? It's possible for a cable to be marginal -- good enough for 100 mbps but not good enough for gigabit. What sort of error count do you get from the connection when you do a speed test with the other system? Barring that, get a decent cable tester to make sure there are no broken wires in that long cable.

Try a speed test between your Gentoo laptop and some other device in your home, with cat5e cable or better. You should be able to get close to wire speed, 995 mbps or so.

Edit: You could also have water somewhere in that long cable, especially if it's barried without some sort of conduit.

Jaglover · Posted: Fri Dec 29, 2017 8:06 pm Post subject:

1clue,

did you notice another laptop worked with this cable at Gbit speed. It would be interesting to see if there is packet loss, though.
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1clue · Advocate Joined: 05 Feb 2006 Posts: 2569

Sorry for being a pain.

What is at the other end of the link? Is it a WAN connection with a roughly 100 mbps contract? Or is it a LAN over there, with some other piece of gigabit-capable equipment you can test against? What is the stated speed of the device you're connected to? If your endpoint is only supposed to be 100mbps then I'll accept that and move on.

If I saw 118 mbps across that link and it was a switch at the other end with another group of equipment, I would not call that gigabit performance. It may or may not be better than 100mbps hardware can do, but as far as gigabit is concerned that is a distinctly poor transfer rate which needs to be addressed unless there is some data rate contract or piece of substandard hardware that can explain it. I wouldn't rule the cable speed out as a potential contributing factor for the connectivity issues.

Your cable's performance could be degraded by any number of things:

A cat5 cable (100 mbps) instead of cat5e (gigabit) may work slightly better than rated speed over that distance, or it may be slower.
Water in the cable will degrade speed
Burying an indoor cable will eventually lead to a degraded connection.
A kink in the cable
A single broken wire can give gigabit in one direction and only 100mbps in the other.
A smashed cable, where the insulators were flattened but not pierced, with wires pressed together, will change the capacitance briefly which translates to an attenuated signal. That would matter over that distance.
Oxidized connectors, oxidized cables.

Jaglover · Posted: Fri Dec 29, 2017 9:26 pm Post subject:

Yeah my bad, somehow I failed to notice the real speed. Cable is almost certainly the culprit here and the whole issue has nothing to do with software or operating system, hardware handshake is failing. The other laptop somehow manages to do it, but there must be huge packet loss, thus the actual speed is miserable.
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NeddySeagoon · Posted: Fri Dec 29, 2017 9:56 pm Post subject:

sigra,

Can you take the Gentoo laptop to the other end of your long cable and connect it with a short cable, just for testing.
Connect it to the same port as the long cable.

A 102 meter ethernet cable is over the maximum specification limit. It will need to be in pristine condition.
No kinks or other damage to cause reflections.

1G and 100Mbit both use the same symbol rate on the wire. 1G packs in more data per symbol and uses all eight wires but the clock speeds are identical.
10Mb and 100Mbit only use 4 of the eight wires. pins 1,2 3 and 6.

You mention snow on the cable. That will increase the transmission losses.

Use ethertool on the Gentoo system to force 10Mbit, then 100Mbit, with full and half duplex.
Keep an eye on the error rate at these low speeds.

If this is the first time that 1G has been attempted on the long cable, you no nothing about the 4 wires that have been lying unused.

At 10Mb and 100Mbit, you might get away with 4 random wires in use.
With 1G, the pairing is important, there is a lot more crosstalk when pairing is not honoured and !G has twice as many signals.
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bunder · Bodhisattva Joined: 10 Apr 2004 Posts: 5937

Try turning off auto negotiation for your switch as well.

sigra · Tux's lil' helper Joined: 03 Feb 2006 Posts: 137

sigra · Tux's lil' helper Joined: 03 Feb 2006 Posts: 137

NeddySeagoon · Posted: Sun Jan 07, 2018 7:47 pm Post subject:

sigra,

Your 100 Mbit/s download and 10 Mbit/s upload service can be terminated in a box that gives a 1G link to the 102m cable.
What does the equipment at the far end of the 102m cable provide?

If its a 1 Gbit link, it will use all 8 wires. If its only 100Mbit/10Mbit, it will only use wires 1,2 3 and 6.
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Computer users fall into two groups:-
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