Ethernet Cable not detected in Ubuntu 14.04 LTS

Question

Ubuntu 14.04 does not detect the ethernet lan cable . Windows detects the same ethernet lan cable. Although ubuntu detects a lan cable which came in the box with router. Please help
Here's the output of 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
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: 10Mb/s
Duplex: Half
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: no

sudo lshw -C network:

      description: Ethernet interface
      product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
   vendor: Realtek Semiconductor Co., Ltd.
   physical id: 0.1
   bus info: pci@0000:05:00.1
   logical name: eth0
   version: 14
   serial: 08:9e:01:e1:0a:57
   size: 10Mbit/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=half firmware=rtl8411-2_0.0.1 07/08/13 latency=0 link=no multicast=yes port=MII speed=10Mbit/s
   resources: irq:62 ioport:3000(size=256) memory:b0404000-b0404fff memory:b0400000-b0403fff

ifconfig -a :

eth0      Link encap:Ethernet  HWaddr 08:9e:01:e1:0a:57  
      UP BROADCAST MULTICAST  MTU:1500  Metric:1
      RX packets:0 errors:0 dropped:0 overruns:0 frame:0
      TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

lo        Link encap:Local Loopback  
      inet addr:127.0.0.1  Mask:255.0.0.0
      inet6 addr: ::1/128 Scope:Host
      UP LOOPBACK RUNNING  MTU:65536  Metric:1
      RX packets:626 errors:0 dropped:0 overruns:0 frame:0
      TX packets:626 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:0 
      RX bytes:61833 (61.8 KB)  TX bytes:61833 (61.8 KB)

wlan0     Link encap:Ethernet  HWaddr 48:d2:24:a1:1b:4f  
      inet addr:192.168.159.8  Bcast:192.168.159.255  Mask:255.255.252.0
      inet6 addr: fe80::4ad2:24ff:fea1:1b4f/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:63929 errors:0 dropped:719 overruns:0 frame:0
      TX packets:7323 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:11495871 (11.4 MB)  TX bytes:1100882 (1.1 MB)

Answer 1

I had a problem like this before, and the issue was related to Realtek ethernet cards.

Here's how I fixed my issue:

1. ran this command that enabled my Internet access: sudo ethtool -s eth0 speed 100 duplex full

2. followed this guide for a permanent fix

Not sure if it'll help you, but it's worth a try.

Answer 2

After hours of trials and errors, I finally managed to get the my Ethernet connection working. Here are the steps:

1. Edit /etc/network/interfaces ( sudo nano /etc/network/interfaces ), add the following 2 lines:

   allow-hotplug eth0
   iface eth0 inet dhcp
   

2. Install Avahi library:

   sudo apt-get update
   sudo apt-get install libavahi-compat-libdnssd-dev
   

3. Edit /etc/rc.local ( gksudo gedit /etc/rc.local ), add the following line:

   avahi-autoipd --daemonize --syslog eth0
   

   one line above exit 0

4. Reboot

5. After reboot, check the network interfaces, by using the command:

   ifconfig -a
   

   eth0, lo, and wlan0 should be listed.
   If eth0:avahi is also listed (usually with inet addr:169.254.5.215), then basically you are ready to go.
   If eth0:avahi is NOT listed, then enter the command:

   sudo avahi-autoipd --daemonize --syslog eth0
   

   After some moments, eth0:avahi will appear when ifconfig -a is run, and you are ready to go. Connect the Ethernet cable on your computer, and you can try ping some IP address on the network.