I'm connecting an Ubuntu 12.04 and a Lubuntu 15.? machine via direct ethernet and have had no success. I have pop-up notifications that 'connection is established' on one machine, but I cant share internet, ping, share folders etc., and have immediate disconnection on the other machine.
The error I get when I ping from one machine is: ping: sendmsg: Operation not permitted
I usually get 'unresponsive' when I ping from the other.
I have tried a crossover adapter, I have used the same cable to connect other machines, have deleted iptables, set it to allow ip forwarding, etc, and still nothing works.