For each NIC on the node, you must create an interface, specifying the interface's MAC address.
$ nova baremetal-interface-add 1 aa:bb:cc:dd:ee:ff +-------------+-------------------+ | Property | Value | +-------------+-------------------+ | datapath_id | 0 | | id | 1 | | port_no | 0 | | address | aa:bb:cc:dd:ee:ff | +-------------+-------------------+