From  your diags (thanks for posting those btw), there is this line: Mar 30 22:05:36 Tower kernel: ixgbe: Intel(R) 10 Gigabit PCI Express Network Driver - version 5.1.0-k I'd be curious what version your Ubuntu install is using.   Here's why I'm asking.  There are two "ixgbe" drivers: one in-tree linux kernel driver, and one available from the Intel download site.  The Intel download is currently at version 5.3.6.   This is something which is fairly common in the linux