Under Ubuntu 12.04 LTS, I would, whenever I wanted to connect a different computer to the Internet, unplug the Ethernet cable and plug it into the other computer. When I wanted to use Ubuntu again, I would plug the cable back into the Ubuntu machine. The network applet would easily negotiate a new connection, even after several days of being disconnected.
I upgraded to Ubuntu 13.10 because some kind of malware infected 12.04, don't know how. In any case, if I unplug it for more than 5 minutes or so, I can no longer switch the Ethernet cable between computers without losing the Ethernet connection on the 13.10 machine.
When the connection is working, the Networking applet (top toolbar) shows:
[dimmed] Ethernet Network Ethernet Connection 1 Disconnect VPN Connections [checked] Enable Networking Connection Information Edit Connections...
If I unplug the cable, after a few minutes several of the above entries disappear or get dimmed out:
[dimmed] Ethernet Network [dimmed] Disconnect Enable Networking [dimmed] Connection Information Edit Connections...
If I click Enable Networking it has no effect:
Can't get a connection. If I click Edit Connections, then delete/add Ethernet Connection on
eth0, it still doesn't work. I tried
ifdown to no effect. The only way to get back online is to re-boot.
Surely there is a better way. Any help would be appreciated.