hi mate thanks for taking the time to reply to my post, take a look at cpu temp app if you have it and see what temperature your nic is running at. I have stumbled across what appears to be a card overheating issue, my 10gbe nic was running at 104 deg C which is over the threshold where it automatically shuts off the network connection. it appears from another o/s forum that previous versions of the drivers may have not had visibility of this and would quite happily let the card run at silly temps, the new linux kernel may have updated the driver to a more recent one in which temperature control is a thing, it will not reset until restart. I have a 40mm fan on the way from amazon, I will keep you posted on the results.