I have a Dell T320 connected directly to another computer via their gigabit ethernet cards, both running Ubuntu 14.04.
At seemingly random occasions, when transferring data constantly from the Dell to the other computer (several hundred MB’s), the connection dropped both using NFS and ssh. It seemed to be a software problem since restarting the network interface on the Dell fixed the problem (temporarily).
I couldn’t find a pattern but when I was running two tasks concomitantly that made quite a few reads and writes via ethernet over an hour or so, I repeatedly saw the network interface crash. On other light or heavy loads I couldn’t reproduce the problem.
Searching online, I found many reports of similar problems. It’s still unclear to me whether this is a problem with the tg3 driver or a bug in this chipset.
In any case, I decided to install another ethernet card on the Dell. Now, NIC’s for this server are >$100. The solution that I hope will work long-term and has survived the situation above is a cheap (~$15) USB Ethernet adapter connected to a USB 2.0 port.
I am using an Asix AX88179, which required downloading (http://www.asix.com.tw/FrootAttach/driver/AX88179_178A_LINUX_DRIVER_v1.14.2_SOURCE.tar.gz), compiling and installing (very easy) a driver, although I read somewhere that kernels >3.9 don’t need the compiled driver. According to iperf I’m getting gigabit speeds and looking at bmon I don’t notice a performance difference compared to the original card.
So here’s my suggestion if you’re having problems with your original Dell NIC and don’t want to spend much on a solution: buy a USB gigabit Ethernet adapter for $15!
One note: I had to reboot the system after installing the driver to obtain gigabit speeds.