Thank you, Rick. 

1) Of course the first thing i did was replacing the cabling, plugging into another port and even into another switch.

2) I put a script changing autoneg in /etc/NetworkManager/dispatcher.d/. But I'll try what you adviced and have a look. 

вт, 27 окт. 2015 г. в 20:08, Rick Stevens <ricks@alldigital.com>:

On 10/27/2015 05:08 AM, Kseniya Blashchuk wrote:
> Now something strange happens - auto negotiation automatically turns on
> after a while. Cannot distinguish what changes this value. I
> added ETHTOOL_OPTS="autoneg off speed 100 duplex full" to the
> ifcfg-Wired_connection_1 config. But seems it doesn't work.
> Am I doing something wrong?

I haven't had to chase this in a long time, but I see two possible
issues:

1) Replace your network cable. Gigabit does put more "strain" on the
cable and if it's flaky (the cable itself or, more likely, the
connectors), you could have issues--especially if it's solid at 100Mbps
but not at 1000Mbps. I've had that issue many times in the past.

2) I had always put the options in the modprobe.d/whatever.conf file so
it was tied to the driver regardless of which network device the kernel
decided to call it (what an absolutely idiotic concept to rename the
devices at boot).

I've never put ETHTOOL_OPTS in a network-scripts/ifcfg-XXX file. Having
said that, I took a quick look at the scripts and it appears that
invoking ethtool is dependent on the presence of a "DEVICE=" line in
that file (well, really on the value of "${REALDEVICE}"). If you don't
have that line, then ethtool isn't called with the "-s" flag to set
parameters as it doesn't know which physical device to apply them to.

Try buggering the ifcfg-Wired_connection_1 file and insert a

        DEVICE=enp2s0

line and try it again. This is just a guess, mind you.

> вт, 27 окт. 2015 г. в 10:34, Joe Zeff <joe@zeff.us <mailto:joe@zeff.us>>:
>
>     On 10/27/2015 12:27 AM, Kseniya Blashchuk wrote:
>      > BTW, I thought maybe its not a driver but a NIC issue and some of the
>      > pins dont work properly. Maybe anybody knows how to check if all NIC
>      > pins are working?
>
>     I have a friend who does all of my hardware work once it gets past the
>     card swapping phase.  (That I can do myself.)  Some of his wire-wrap
>     work is heading out of the Solar System, and he doesn't even try to
>     troubleshoot things like that; he just replaces the card if possible.
>     However, as the card works fine at 100 Mbps but not at 1000, I doubt
>     that it's hardware.
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