def METHOD_NAME(self, gateway):
    """  Add a default route
    :param str gateway
    :return: bool
    """
    if not gateway:
        raise Exception("Gateway cannot be None.")
    if self.defaultroute_exists():
        return False
    else:
        cmd = "default via " + gateway
        logging.info("Adding default route")
        self.set_route(cmd)
        return True