def get_out_net_id(cls, tenant_id):
        """Retrieve the network ID of OUT network. """
        if 'out' not in cls.ip_db_obj:
            LOG.error("Fabric not prepared for tenant %s", tenant_id)
            return None
        db_obj = cls.ip_db_obj.get('out')
        out_subnet_dict = cls.get_out_ip_addr(tenant_id)
        sub = db_obj.get_subnet(out_subnet_dict.get('subnet'))
        return sub.network_id