Recently I installed ubuntu 14.04 on my new laptop, lenovo L440.

will doing the installation I used wifi.

With a wifi everything works perfectly, the problem is when i plugged a lan cable.

The OS recognized the new connection and I can see the 2 arrows, I am also get a connection for few minutes/seconds.

The problem is that I can't connect to internet after minutes. The connection indicator (2 arrows) still shows me I am connect to the network. Also if i press on the connection it reconnect but drops again.

Any suggestion will be greatly appreciate.

  • Did you disable the wifi connection during the cable test? If not, then it would probably be due to dropped packages. If you did, then I'd try pinging your default gateway to see if you really are connected. Aug 27, 2014 at 12:23

2 Answers 2


I have been edited the file NetworkManager.conf

from /etc/NetworkManager/NetworkManager.conf




  • didn't work for me! Again, i don't know what it does? Feb 16, 2017 at 10:57

I recommend this answer: https://askubuntu.com/a/736589/194156

At least it does not take long to try: go to Network Manager, and set MTU size to 8192 bytes. And reboot.

This worked instantly for me. After I changed MTU size back to "Automatic", it stopped working immediately. So that must be it.

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