You can configure both fibre-channel or iSCSI-attached hosts to the cluster.
If you are configuring a host object on a fibre-channel attached host, ensure that you have completed all zone and switch configuration. Also test the configuration to ensure that zoning was created correctly.
If you are configuring a host object on the cluster that uses iSCSI connections, ensure that you have completed the necessary host-system configurations and have configured the cluster for iSCSI connections.