'A NAT/firewall forwarding rule.
@note: This is a non-standard extension API, and only works for
CloudStack.
:param      node: Node for rule
:type       node: :class:`Node`
:param      id: Rule ID
:type       id: ``int``
:param      address: External IP address
:type       address: :class:`CloudStackAddress`
:param      protocol: TCP/IP Protocol (TCP, UDP)
:type       protocol: ``str``
:param      start_port: Start port for the rule
:type       start_port: ``int``
:param      end_port: End port for the rule
:type       end_port: ``int``
:rtype: :class:`CloudStackIPForwardingRule`'

def __init__(self, node, id, address, protocol, start_port, end_port=None):

    self.node = node
    self.id = id
    self.address = address
    self.protocol = protocol
    self.start_port = start_port
    self.end_port = end_port
