def create_cluster_logical_device_ids(core_id, switch_id):
    """
    Creates a logical device id and an OpenFlow datapath id that is unique 
    across the Voltha cluster.
    The returned logical device id  represents a 64 bits integer where the
    lower 48 bits is the switch id and the upper 16 bits is the core id.   For
    the datapath id the core id is set to '0000' as it is not used for voltha
    core routing
    :param core_id: string
    :param switch_id:int
    :return: cluster logical device id and OpenFlow datapath id
    """
    switch_id = format(switch_id, '012x')
    core_in_hex=format(int(core_id, 16), '04x')
    ld_id = '{}{}'.format(core_in_hex[-4:], switch_id[-12:])
    dpid_id = '{}{}'.format('0000', switch_id[-12:])
    return ld_id, int(dpid_id, 16)