<!-- If you need to report a security issue please visit https://github.com/apache/dubbo/security/policy -->

- [x] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.

## Ask your question here
操作步骤如下：
1. k8s环境下，consumer端开启mesh模式
2. consumer端需要调用多个provider
3. provider有应用级注册和接口级注册，并且需要的provider不再同一个namespace下
4. 原有项目存在dubbo2.6与3.1多版本间的相互调用，在开启消费端mesh（dubbo3.1）后，无法调用到2.6的服务提供者

**问题：**

1. 如何实现在一个consumer下，调用多个namespace下的provider，并且provider有应用级注册和接口级注册
2. dubbo3.1消费端在开启mesh后，如何调用版本是2.6的服务提供者
* @see RegistryConstants#PROVIDED_BY
     */
    String[] providedBy() default {};
    /**
     * The service port of the provider
     *
     * @see AbstractReferenceConfig#providerPort
     * @since 3.1.0
     */
    int providerPort() default -1;
    /**
     * the scope for referring/exporting a service, if it's local, it means searching in current JVM only.
     *
     * @see org.apache.dubbo.rpc.Constants#SCOPE_LOCAL
     * @see org.apache.dubbo.rpc.Constants#SCOPE_REMOTE
     */
    String scope() default "";
    /**
     * Weather the reference is refer asynchronously
     */
    boolean referAsync() default false;
    /**
     * unload Cluster related in mesh mode
     *
     * @see ReferenceConfigBase#unloadClusterRelated
     * @since 3.1.0
     */
    boolean unloadClusterRelated() default false;
}