Failed to log into NFC server

Problem

A new vCenter/ESXi deployment. Attempting to upload an ISO to a ESXi datastore by connecting through vCenter fails with Failed to log into NFC server. Connecting to the target ESXi server directly leads to a successful transfer.

Solution

The root problem is that my desktops could not resolve the FQDN of the ESXi server provided by the vSphere server, even though the DNS in the VMware cluster was all internally consistent. This blog post gave me the hint I needed.

My VMware environment is set up with its own AD tree separate from the AD tree that my desktops use. As a side-effect, my desktops cannot resolve the fully qualified names of my VMware systems since the DNS zone is not in our search path and our local AD servers didn't know where to find the VMware AD servers.

I added a Conditional Forwarder in my desktop AD's DNS service indicating the zone name of the VMware AD along with the AD server IP addresses, and now the transfers work.

I conclude that the root problem is that my desktops could not resolve the FQDN of the ESXi server provided by the vSphere server, even though the DNS in the VMware cluster was all internally consistent.