def add_cluster_virtual_interface(self, interface_id, cluster_virtual=None,
                    network_value=None, nodes=None, zone_ref=None, comment=None):
        """
        Add a tunnel interface on a clustered engine. For tunnel interfaces
        on a cluster, you can specify a CVI only, NDI interfaces, or both.
        This interface type is only supported on layer 3 firewall engines.
        ::

            Add a tunnel CVI and NDI:

            engine.tunnel_interface.add_cluster_virtual_interface(
                interface_id_id=3000,
                cluster_virtual='4.4.4.1',
                network_value='4.4.4.0/24',
                nodes=nodes)

            Add tunnel NDI's only:

            engine.tunnel_interface.add_cluster_virtual_interface(
                interface_id=3000,
                nodes=nodes)

            Add tunnel CVI only:

            engine.tunnel_interface.add_cluster_virtual_interface(
                interface_id=3000,
                cluster_virtual='31.31.31.31',
                network_value='31.31.31.0/24',
                zone_ref='myzone')

        :param str,int interface_id: tunnel identifier (akin to interface_id)
        :param str cluster_virtual: CVI ipaddress (optional)
        :param str network_value: CVI network; required if ``cluster_virtual`` set
        :param list nodes: nodes for clustered engine with address,network_value,nodeid
        :param str zone_ref: zone reference, can be name, href or Zone
        :param str comment: optional comment
        """
        interfaces = [{'cluster_virtual': cluster_virtual, 'network_value': network_value,
                       'nodes': nodes if nodes else []}]
        interface = {'interface_id': interface_id, 'interfaces': interfaces,
            'zone_ref': zone_ref, 'comment': comment}
        
        tunnel_interface = TunnelInterface(**interface)
        self._engine.add_interface(tunnel_interface)
Add a tunnel interface on a clustered engine. For tunnel interfaces
        on a cluster, you can specify a CVI only, NDI interfaces, or both.
        This interface type is only supported on layer 3 firewall engines.
        ::

            Add a tunnel CVI and NDI:

            engine.tunnel_interface.add_cluster_virtual_interface(
                interface_id_id=3000,
                cluster_virtual='4.4.4.1',
                network_value='4.4.4.0/24',
                nodes=nodes)

            Add tunnel NDI's only:

            engine.tunnel_interface.add_cluster_virtual_interface(
                interface_id=3000,
                nodes=nodes)

            Add tunnel CVI only:

            engine.tunnel_interface.add_cluster_virtual_interface(
                interface_id=3000,
                cluster_virtual='31.31.31.31',
                network_value='31.31.31.0/24',
                zone_ref='myzone')

        :param str,int interface_id: tunnel identifier (akin to interface_id)
        :param str cluster_virtual: CVI ipaddress (optional)
        :param str network_value: CVI network; required if ``cluster_virtual`` set
        :param list nodes: nodes for clustered engine with address,network_value,nodeid
        :param str zone_ref: zone reference, can be name, href or Zone
        :param str comment: optional comment