My eth0 has gone and I don't have internet and network connection

I had internet connection, but when I upgraded my VGA and restarted my PC then everything for eth0 has gone.

When I used ifdown:

 ifdown: interface eth0 not configured 

Is there something I could do?

EDIT:
Content of /etc/network/interfaces

auto lo iface lo inet loopback 

When I ifconfig I don't have these lines:

inet addr:192.168.1.5 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::219:5bff:fe5e:a5e/64 Scope:Link 

In the Terminal typed:

sudo gedit /etc/network/interfaces 

and then added these lines in the bottom:

auto eth0 iface eth0 inet dhcp 

then I typed:

sudo ifdown eth0 sudo ifup eth0 

when I send the second command I received the below message:

No DHCPOFFERS received No working leases in persistent database - sleeping 

Any help?

4 Answers

Try:

sudo dpkg-reconfigure network-manager 

If that doesn't work boot from a live CD, back up your old network settings, clear out any system connection file and copy over the ones from the live CD.

Change to Root:

sudo su 

backup:

mv /media/<Name of your Ubuntu Partion>/etc/NetworkManager/NetworkManager.conf /media/<Name of your Ubuntu Partion>/etc/NetworkManager/NetworkManager.conf.broken 

clear:

rm /media/<Name of your Ubuntu Partion>/etc/NetworkManager/system-connections/* 

copy:

cp /etc/NetworkManager/NetworkManager.conf /media/<Name of your Ubuntu Partion>/etc/NetworkManager/NetworkManager.conf cp /etc/NetworkManager/system-connections/* /media/<Name of your Ubuntu Partion>/etc/NetworkManager/system-connections/ 

Can you try to edit /etc/network/interfaces and put it the default settings for DHCP below?

# This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet dhcp 

Try to restart the networking service with:

sudo service network-manager stop 

If it doesn't work, then try:

sudo service network-manager stop 

Then the following command to bring up the interface:

sudo ifconfig eth0 up 

Then, force Ubuntu to ask for a new DHCP lease with:

sudo dhclient eth0 

Thanks . It worked for me.

1. I had the IP address but no internet connection
2. The LAN port was active
3. I had assigned static IP address

My /etc/network/interfaces had the following content:

source /etc/network/interfaces.d/* # The loopback network interface auto lo iface lo inet loopback # The primary network interface iface enp4s8 inet static address 192.168.2.251 netmask 255.255.255.0 network 192.168.2.0 

I was having ifconfig output as (this is manual edit - it was somewhat like this)

~$ ifconfig enp4s8 Link encap:Ethernet HWaddr 00:19:d1:73:b7:11 inet addr:192.168.2.251 Bcast:192.168.2.251 Mask:255.255.255.0 inet6 addr: fe80::219:d1ff:fe73:b711/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:13181 errors:0 dropped:0 overruns:0 frame:0 TX packets:8462 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:16690503 (16.6 MB) TX bytes:884958 (884.9 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:317 errors:0 dropped:0 overruns:0 frame:0 TX packets:317 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1 RX bytes:40111 (40.1 KB) TX bytes:40111 (40.1 KB) 

I changed the /etc/network/interfaces to:

source /etc/network/interfaces.d/* # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto enp4s8 #iface enp4s8 inet dhcp #iface enp4s8 inet static #address 192.168.2.251 #netmask 255.255.255.0 #network 192.168.2.0 #broadcast 192.168.2.255 #gateway 192.168.2.1 #dns-nameservers 192.168.2.1 

Then I followed the steps included in the answer above:

sudo service network-manager stop sudo ifconfig enp4s8 up sudo dhclient enp4s8 sudo service network-manager start 

This is when I got the connection to the network, these steps worked.

FYI - The Live CD also had internet connection. I did not copy the files from Live CD.

I've had quite a similar issue after an Ubuntu (12.04) updtate.

I resolved it by logging in recovery mode, then activate the network, then typing into the console:

sudo apt-get remove network-manager sudo apt-get update sudo apt-get install network-manager