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I've got problem with my Ethernet connection on Ubuntu, although connection works fine on my dualboot Win 7 and I should say, that my connection on Ubuntu was working few days ago , but now it won't connect at all. It say that I'm "Disconnected".

ifconfig shows following output:

eth0      Link encap:Ethernet  HWaddr e4:11:5b:3a:73:b0  
          inet6 addr: fe80::e611:5bff:fe3a:73b0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:31 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:5755 (5.7 KB)

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:39 errors:0 dropped:0 overruns:0 frame:0
          TX packets:39 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:4065 (4.0 KB)  TX bytes:4065 (4.0 KB)

wlan0     Link encap:Ethernet  HWaddr ac:81:12:e3:ce:5a  
          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)

cat /etc/network/interfaces

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

I would appreciate any help!

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  • There is no IP address associated with the connection. How do you get IP? DHCP/static?
    – heemayl
    Feb 16, 2015 at 22:39
  • I should get it automatically when i connect my ethernet cable. It used to work that way before. I thought after reading few topics with same problem (not working internet) I played with /etc/network/interfaces and add to "auto lo iface lo inet loopback " these lines ,which recommend in the topics : " auto eth0 iface eth0 inet static " ,but it won't work. After Ubuntu get restarted ,It gets loaded without network configuration.
    – Umbra
    Feb 16, 2015 at 22:47
  • Please add the entries of /etc/network/interfaces to your question. Did you configure anything manually via graphical network manager (normally it will use DHCP unless changed manually)?
    – heemayl
    Feb 16, 2015 at 22:59
  • No,I didn't. I don't know myself ,why it isn't working.
    – Umbra
    Feb 16, 2015 at 23:31
  • Usually, more recent versions of Ubuntu have moved away from using hard -coded networking information in /etc/network/interfaces to using NetworkManager (or an alternative). Have you tried configuring it through the GUI?
    – Aaron D
    Feb 16, 2015 at 23:40

1 Answer 1

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Are you using a graphical desktop or are you on server? If server then you can safely edit /etc/network/interfaces to something like:

for dhcp :

auto eth0
iface eth0 inet dhcp

for static IP:

auto eth0
iface eth0 inet static
           address <ip>
           netmask <netmask>
           gateway <gateway_ip>
           dns-nameservers <dns_ip> <dns_ip>

However if you have a desktop then they use NetworkManager daemon to automagically manage the interfaces and overrides/messes up with /etc/network/interfaces. If so, check your network settings from the desktop tool and don't mess with /etc.

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  • Somehow , after some random changing in network manager settings and reseting LAN settings in Bios , It starts working now. So thank you Sir !
    – Umbra
    Feb 17, 2015 at 9:53
  • No problem, it happen to me that in between updates network manager messed up its database of Wifi logins. Now depending on the desktop, in your home folder you have hidden folders such as .conf, .kde, .gnome, where network manager saves its configuration for your user. Removing the configuration from said folder will make network manager start fresh on the next login. Trouble is, you have to find where it resides.
    – user283885
    Feb 18, 2015 at 16:13

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