Re: Ethernet suddenly limited to 100 Mbps
On 2013-08-18 12:25:59 -0500, Stan Hoeppner wrote:
> On 8/18/2013 10:31 AM, Vincent Lefevre wrote:
> > On my laptop, Ethernet has been limited to 100 Mbps for a few days.
> > Nothing changed on the network side. Just a few upgrades on the laptop
> > (Debian/unstable). Any explanation?
>
> Gigabit ethernet is fully auto negotiating at the hardware level--a
> software update shouldn't cause negotiation to drop to 100. GBE uses
> all 8 conductors of category 5e/6 cabling, fast ethernet uses only 4.
> If it's negotiating to 100, I'd say you have a bad cable, connector
> (cable or receiver port), or switch port.
The Ethernet cable was the same as before, and I've tried a second
one, and it's still 100. I've also tried another port on the switch.
> Given this is a laptop, I make the educated guess that you
> plug/unplug regularly putting wear stress on the cable and
> connectors.
It's not regular (the laptop is usually at home and remains
connected). I take it with me only when I'm off for several days.
But the problem occurred just after being back from holidays,
where I took the laptop with me; I didn't use the Ethernet port
there, but the laptop has moved a lot in the train.
To confirm whether this comes from the laptop, I'll try with the
switch at my lab tomorrow (and I could compare with the desktop
computer, for which the speed is 1000).
> In this case you should check the 8 angled pins in the laptop RJ45
> receptacle to make sure none are broken or bent. If one of the 8 is not
> making solid contact with the corresponding cable connector pin, 100
> Mbps link speed will be the result. If it is damaged the laptop will
> require depot service to desolder and replace the receptacle. If the
> receptacle doesn't appear to be the problem, replace the cable with a
> known good cable or a new cable. Frequent bending of cables during
> insertion/removal can cause stress breakage of the tiny cable conductors
> which are normally 26 or 28 AWG, especially at the termination connector
> junction.
OK, thanks for this very detailed information.
--
Vincent Lefèvre <vincent@vinc17.net> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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