Realtek r8169 always flapping

[Rick Stevens]

On 10/26/2015 09:57 AM, Kseniya Blashchuk wrote:
> Hi everyone!
> I noticed in dmesg that my ethernet link is flapping all the time
> [Oct25 18:55] r8169 0000:02:00.0 enp2s0: link down
> [  +3.131667] r8169 0000:02:00.0 enp2s0: link up
> [Oct25 18:56] r8169 0000:02:00.0 enp2s0: link down
> [  +2.763688] r8169 0000:02:00.0 enp2s0: link up
> [Oct25 18:59] r8169 0000:02:00.0 enp2s0: link down
> [  +3.060069] r8169 0000:02:00.0 enp2s0: link up
> [Oct25 19:00] r8169 0000:02:00.0 enp2s0: link down
> [  +3.559610] r8169 0000:02:00.0 enp2s0: link up
> I changed the cabling, tried to plug into another switch no difference.
> Any ideas will be very appreciated as this flapping brings a lot of
> inconvenience.
> My device in lspci:
> 02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd.
> RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 10)

Uhm, could be a kernel issue or a driver issue. Generally when I see
that sort of thing it's an auto speed or auto duplex negotiation between
the driver and switch that isn't working. You could try forcing the
speed and duplex via something like:

	sudo ethtool -s enp2s0 autoneg off duplex full speed 1000

to set a fixed 1Gbps, full duplex connection and see if that helps
stabilize things. If that works you could try to restart auto
renegotiation via

	sudo ethtool -s enp2s0 autoneg on
	sudo ethtool -r enp2s0

The first comment re-enables autonegotiation, the second forces a
renegotiation.
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- Rick Stevens, Systems Engineer, AllDigital    ricks at alldigital.com -
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