You have a Windows 2012 server running as a VMware ESXi guest and the Windows 2012 VM loses access to the network without any obvious cause.
Windows 2012 does not like the emulated E1000 NICs that are often used for ESXi guests; it does not have the same issues with a VMXNet NIC. So we need to change the virtual NIC.
- Make sure you have documented the guests’s network configuration (e.g. static IP, DNS servers, etc.).
- Log on to a physical machine and connect to the ESXi host using the VMware vSphere Client.
- Edit the settings for the guest; select the existing E1000 NIC and click the “Remove” button.
- Click the Add button, the select Ethernet Adapter; click Next.
- Select either “VMXNET 2 (Enhanced)” or “VMXNET 3” as the Adapter Type and click Next.
- Click Finish to add the new NIC.
- Click OK to save the changes to the guest.
- The guest should start using the new NIC immediately without any additional configuration. If not, reconfigure the new NIC with the settings you documented above. A reboot may be a good idea.