Enabling gigabit ethernet on RTL8111/8168/8411

Question

I am completely new to Ubuntu, but I've installed Ubuntu 16.04 on an old machine mainly to be used as a Plex server for large movie files.

When I go to the ethernet settings I can clearly see ethernet is only running at 100mb/s. Here is some information about the network configuration:

*-network               
   description: Ethernet interface
   product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
   vendor: Realtek Semiconductor Co., Ltd.
   physical id: 0
   bus info: pci@0000:04:00.0
   logical name: enp4s0
   version: 06
   serial: bc:5f:f4:e9:a0:e4
   size: 100Mbit/s
   capacity: 1Gbit/s
   width: 64 bits
   clock: 33MHz
   capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
   configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl_nic/rtl8168e-2.fw ip=192.168.1.68 latency=0 link=yes multicast=yes port=MII speed=100Mbit/s
   resources: irq:24 ioport:e000(size=256) memory:d0004000-d0004fff memory:d0000000-d0003fff

How can I enable gigabit ethernet?

edit:

Settings for enp4s0:
Supported ports: [ TP MII ]
Supported link modes:   10baseT/Half 10baseT/Full 
                        100baseT/Half 100baseT/Full 
                        1000baseT/Half 1000baseT/Full 
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes:  10baseT/Half 10baseT/Full 
                        100baseT/Half 100baseT/Full 
                        1000baseT/Half 1000baseT/Full 
Advertised pause frame use: Symmetric Receive-only
Advertised auto-negotiation: Yes
Link partner advertised link modes:  10baseT/Half 10baseT/Full 
                                     100baseT/Half 100baseT/Full 
Link partner advertised pause frame use: Symmetric Receive-only
Link partner advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Full
Port: MII
PHYAD: 0
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: pumbg
Wake-on: d
Current message level: 0x00000033 (51)
               drv probe ifdown ifup
Link detected: yes

Solution

You can check the capability of your ethernet hardware quite easily. E.g., To check the ethernet hardware device eth0

sudo ethtool eth0
Settings for eth0
    Supported ports: [ TP MII ]
    Supported link modes:   10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Supported pause frame use: No
    Supports auto-negotiation: Yes
    Supported FEC modes: Not reported
    Advertised link modes:  10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Full 
    Advertised pause frame use: Symmetric Receive-only
    Advertised auto-negotiation: Yes
    Advertised FEC modes: Not reported
    Link partner advertised link modes:  10baseT/Half 10baseT/Full 
                                         100baseT/Half 100baseT/Full 
                                         1000baseT/Full 
    Link partner advertised pause frame use: Symmetric
    Link partner advertised auto-negotiation: Yes
    Link partner advertised FEC modes: Not reported
    Speed: 1000Mb/s
    Duplex: Full
    Port: MII
    PHYAD: 32
    Transceiver: internal
    Auto-negotiation: on
    Supports Wake-on: pumbg
    Wake-on: g
    Current message level: 0x00007fff (32767)
                   drv probe link timer ifdown ifup rx_err tx_err tx_queued intr tx_done rx_status pktdata hw wol
    Link detected: yes

Once you established that your hardware and linux driver do support the gigabit speed, you can proceed to check the cable you use and the switch or router you are connecting to.

To force 1000mb full duplex, for enp4s0 try

sudo ethtool -s enp4s0 speed 1000 duplex full

This may or may not work. It may work if your cable is marginal capable of doing 1000mb. Even if this work, you should get a better cable to ensure reliable gigabit connection, otherwise it may renegotiate down to a low speed when errors occur.

Comments

[N0rbert]

Are you sure that cable is capable to run on 1 Gbit/s?

[Simon]

No, I'm not sure. They're cables I've had lying around for a while. I will pick up a couple of new gigabit cables to see if that fixes the issue. Thanks

[Terrance]

Ethernet cable for gigabit should be at least a CAT-5e but best to go with a CAT-6 type cable.

[Simon]

Hi Bernard. I receive 'Cannot get device settings: No such device' when I try this

[N0rbert]

Change eth0 to yours enp4s0.

[Bernard Wei]

As @N0rbert indicated, use your ethernet device in the place of eth0, such as sudo ethtool enp4s0

[Simon]

Thanks. I've updated the main post with that info. I see the 'Link partner advertised link modes' does not include the 1000baseT/Full option

[Bernard Wei]

@Simon Everything indicates your device and software can handle gigabit network. The hardware is negotiating the speed down to 100 megabits. I added some steps to foce gigabit speed if your cable is marginally supporting gigabits.

[Simon]

Thanks. I will give your suggestion a try to get it working temporarily, and order some new cat6 cables.