Please provide some more details about the environment, i.e. nested on what (VMware Workstation, ESXi, ...) Which version (host OS, guest OS, Hypervisors) do you use? How did you configure networking for the nested hosts (stanard vSwitch, Distributed switches)? What may help are the configuration (.vmx) files for the nested ESXi hosts, so please attach them to a reply post.
André
Note: Discussion moved from vSphere Newbie to Nested Virtualization