I have a Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06) in my new Ubuntu Trusty (14.04.1) server. As you can see here:
root@orac:/home/jj5# lspci
...
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06)
...
I was having a problem with the card only supporting 100baseT speeds. I downloaded and installed the Realtek driver (and rebooted):
# bunzip2 r8168-8.039.00.tar.bz2
# tar xf r8168-8.039.00.tar
# cd r8168-8.039.00
# ./autorun.sh
# reboot
That didn’t fix the problem.
I installed the ethtool package and ran it:
# apt-get install ethtool
# ethtool p2p1
Settings for p2p1:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised pause frame use: Symmetric Receive-only
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 0
Transceiver: internal
Auto-negotiation: on
MDI-X: Unknown
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000033 (51)
drv probe ifdown ifup
Link detected: yes
As you can see the speed is 100Mb/s, not 1000Mb/s. It says that 1000baseT full duplex is supported. I tried forcing the speed:
# ethtool -s p2p1 speed 1000 duplex full advertise 0 autoneg off
But that didn’t work. The ethtool program reported the card was still operating and 100Mb/s.
Then I tried plugging in a different cable… and that fixed the problem!