Symptoms:
VMware vSphere ESXi
VMware vCenter Server
The error message "Virtual Ethernet Card 'Network Adapter 1' is not supported" is a benign warning that can be safely ignored.
The error occurs when the vCenter Server tries to migrate a virtual machine to a host that does not support the network adapter type of the virtual machine.
However, the networking will still work correctly after the vMotion is complete.
The error message specifically mentions that the issue is with the guest OS on the selected host.
This is because the guest OS determines which network adapter types are supported.
For example, if the guest OS is a Linux distribution that does not support e1000, then the vCenter Server will generate the error message even if the host supports e1000.
This is not a limitation of the host in general, but of the virtual machine's configured guest operating system on the selected host. Check the Guest OS Compatibility Guide to know which network adapter is supported for the guest operating system.
If you see this error message, you can safely ignore it and proceed with the vMotion. The networking will still work correctly after the vMotion is complete.
Here are some additional details about the error message:
The error message is not a limitation of the host in general. The host may support the network adapter type, but the guest OS may not.
The error message is specific to the virtual machine's configured guest OS on the selected host. If you migrate the virtual machine to a different host with a different guest OS, the error message may not appear.
To resolve the issue, shutdown the virtual machine and change the network adapter type to one of the supported adapters mentioned in the Compatibility Guide. Refer Choosing a network adapter for your virtual machine