11.10networking
On both my home and work networks, if I plug in an ethernet cable into my laptop, gnome's network manager starts cycling between saying "Wired network Disconnected" and "wired network Connection Established". It does this back and forth about once every couple seconds.
The network card is Intel Corporation 82579LM Gigabit Network Connection and the laptop is a Dell Precision M6600.
Thanks in advance!
If you're using NetworkManager, it should just work. That said, you will need to set specific settings for your wired connection.
Select your wired connection in the Connection Editor window for NetworkManager (right click on the applet icon, then select Edit Connections). Click Edit, then switch to the IPv4 Settings tab and click the Routes button at the bottom.
You can then force the wired connection to not claim the default gateway (since NM would usually prefer wired over wireless), by checking the "Use this connection only for the resources on its network" checkbox.
Best Answer
I would first start from external causes (Hardware) and work my way into internal causes (Software and internal hardware).
Make sure the cables are correctly plugged in and the cable connectors are correctly made (Should not disconnect if you for example try to slightly pull the cable).
Verify that the cable does not have a huge rotten chewing on it or some mutated monster dropping radiactive goo on the ethernet cable.
Check that the network cards are, if they are PCI, correctly connected. Over exaggerating this but it happened 3 times in my life experience.
After doing this 3 cases then read this post that it might solve the same problem: Sharing any Network Connection starts a connection/disconnection loop
The solution was to update Ubuntu packages and it was solved, not only for sharing connections wirelessly and wired but also for connecting to shared ones or directly to wired/wifi ones.