Member Avatar for goldap

Friends! i m not good enough at linux so far but have got wired net plugging disorder after ubuntu 12.04 installation on my pc. "Cable is unplagged " or "device is not ready " notices tell me nothing. pls explain how to fix the issue by command line "as root" if one n the only password ( created during installation) is available???

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  • Latest Post Latest Post by richard.hiltbrunn

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A focused troubleshooting checklist that builds on ’s and ’s suggestions: start with the physical layer, then gather hardware, driver and kernel diagnostics, then test link and DHCP. On Ubuntu 12.04 the usual culprits are a dead cable/port, the NIC being administratively down, or a missing/incorrect kernel driver (12.04’s older stack can miss drivers for newer NICs).

Useful diagnostic output to collect (run commands as root via sudo):

sudo -i
ip link
ip addr
sudo lshw -class network
lspci -nnk | grep -iA3 network
dmesg | tail -n 80
sudo ethtool <interface-name>
sudo dhclient -v <interface-name>
nmcli device status

What to look for and quick interpretations: an interface showing DOWN or no carrier points at a cable/switch problem or physical link; ethtool shows “Link detected: yes/no” and speed/duplex (no = physical problem). lshw/lspci will show the NIC model and the kernel module in use; if no driver is listed or dmesg reports missing firmware, a driver or firmware package will be needed. If the interface is simply down, bring it up with ip link set dev <interface-name> up and try DHCP with dhclient as above.

Practical checks: try a different cable and switch port, test the same cable on another machine, and try a USB-to-Ethernet adapter if available. Keep command output (trim long logs) for diagnostics but avoid pasting passwords or full MAC addresses. Because this thread refers to Ubuntu 12.04, note the OS is old and may require backported drivers or a newer live image to confirm hardware compatibility.

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Member Avatar for CimmerianX

So the obvious question is, is a cable plugged into the machine? What port is the cable conencted into? eth0? what does ifconfig show?

Member Avatar for richard.hiltbrunn

Go to a terminal or command prompt and type ifconfig, then post the results :)

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