The problem began in last few days. Seemingly if servers is left on for about 6~8 hours (doesn't matter if it is idle or being heavily used; doesn't matter if it is logged in or not logged in) the server will spontaneously lose network connection, and will not see the internet. Repairing the connection does not work. Re-inserting the ethernet plug does not work. We need disable & enable back the NIC. However, disable NIC on certain servers not function so we have restart it to restore the connection. Curiously, when the server loses connection, disable/re-enable NIC or restarting (no power cycle) fixes the problem. When the network connection goes out, there is no indication that the network has lost connectivity. The network icon indicator says the ethernet is connected at 1Gbps. No software has been added or deleted from the machines since these servers setup, save for Microsoft Patches through update.microsoft.com. The servers exhibit this problem regardless of whether they are logged into the AD Domain or logged in as a local administrator. I appreciate any help. Thanks much!!

model of server and NIC? may be a driver issue ...

Hi It sounds like you have a driver issue. Try either rolling back the driver for the NIC, or downloading the latest driver for your NIC. A new driver might have been installed by Windows Update. You can also try to uninstall the NIC from Device Manager and re-install it. Also, don't rule out hardware failure as a possibility, it might be that your NIC is damaged and needs to be replaced. Hope this helps. Regards Lionel

Hi, Thank you for the post. All servers encountered this problem? You describe servers are unable to connect Internet, but not mention if servers could connect other server in the same network. Please try to use tracert command to narrow the failure point, maybe some network device like switch cause the issue. If there are more inquiries on this issue, please feel free to let us know. RegardsRick Tan TechNet Community Support

As an alternative to looking only at the Windows Server side of things, you might also want to check your switches or core haven't had firmware updates. You should also check that you haven't left the network card driver configured to "auto negotiate" the connection speed and duplex, as it's not uncommon to see failed negotiation result in decreased performance and intermittent drop-outs. In addition to manually setting the speed and duplex on the network card, the network port on the switch should be statically configured, so you might need to get your network administrator involved. Cheers, Lain