I recently installed Ubuntu 13.10 (later upgraded to 14.04 in an unsuccessful attempt to fix the problem) and have been having trouble with the wired Internet. Specifically, the Internet connection is dropping intermittently, maybe for 15-90 seconds every minute or two.
Curiously, I never have any problems pinging another computer plugged into the same switch. Only the external Internet drops. However, I don't have any issues with the external Internet when I plug my MacBook into the same Ethernet switch.
It's not a DNS issue, as the issue persists if I try to ping Google by IP address instead of using google.com.
I actually have two network cards in the machine (each with two Ethernet ports). The cards use different drivers, namely e1000e and ixgbe. I encounter the same problem no matter which card I plug into.
I was originally on Ubuntu 13.10 and kernel 3.11. I upgraded to Ubuntu 14.04 and kernel 3.13.0-20, but it didn't fix the problem. I also tried disabling the 3 interfaces (two ports on the other card and the unused port on the active card) and stopping network-manager, but that didn't seem to have an effect either.
There's nothing obvious in /var/logsyslog or kern.log. In particular, the times when the Internet stops and starts again don't lineup with DHCP renewals.
Any ideas? I'm stumped here, so any help would be very much appreciated.