Cisco Application Centric Infrastructure is able to use both LLDP and CDP to automatically discover connections with serviers. This can be especially useful with ESXi servers. The question that often comes up is whether you should use CDP or LLDP to do this discovery. Although a lot of times we recommend trying CDP, it really comes down to the NIC in the server to which you're connecting.
Though we configure the policy in the controller, or APIC, if the NIC you're connecting to doesn't support CDP it's not going to work. So if you're seeing errors with descriptions of "Operational Issues" especially pointing to a NIC, try changing the discovery protocol you're using. Also, make sure that you have the correct protocol configured in vCenter for the vSwitch. Please refer to the VMware documentation for a reference on how to do that.