﻿---
title: Connect to Elasticsearch clusters in the same Elastic Cloud on Kubernetes environment
description: These steps describe how to configure remote clusters between two Elasticsearch clusters that are managed by the same Elastic Cloud on Kubernetes (ECK)...
url: https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/5592/deploy-manage/remote-clusters/eck-remote-clusters
products:
  - Elastic Cloud on Kubernetes
applies_to:
  - Elastic Cloud on Kubernetes: Generally available
---

# Connect to Elasticsearch clusters in the same Elastic Cloud on Kubernetes environment
These steps describe how to configure remote clusters between two Elasticsearch clusters that are managed by the same Elastic Cloud on Kubernetes (ECK) operator.
After the connection is established, you’ll be able to [run CCS queries from Elasticsearch](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/5592/explore-analyze/cross-cluster-search) or [set up CCR](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/5592/deploy-manage/tools/cross-cluster-replication/set-up-cross-cluster-replication).
<note>
  The remote clusters feature requires a valid Enterprise license or Enterprise trial license. Check [the license documentation](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/5592/deploy-manage/license/manage-your-license-in-eck) for more details about managing licenses.
</note>

<admonition title="Note about terminology">
  In the case of remote clusters, the Elasticsearch cluster or deployment initiating the connection and requests is often referred to as the **local cluster**, while the Elasticsearch cluster or deployment receiving the requests is referred to as the **remote cluster**.
</admonition>

To create a remote cluster connection to another Elasticsearch cluster deployed in the same ECK environment, specify the `remoteClusters` attribute in your Elasticsearch spec. In this scenario, the operator automatically orchestrates all required configuration across both clusters, based on the selected security model.
For other remote cluster scenarios with ECK, refer to [Remote clusters on ECK](/elastic/docs-content/pull/5592/deploy-manage/remote-clusters/eck-remote-clusters-landing#eck-rcs-setup).

## Security models

Before you start, consider the [security model](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/5592/deploy-manage/remote-clusters/security-models) that you would prefer to use for authenticating remote connections between clusters, and follow the corresponding steps.
<definitions>
  <definition term="API key">
    For deployments based on Elastic Stack 8.14 or later, you can use an API key to authenticate and authorize cross-cluster operations to a remote cluster. This model uses a dedicated service endpoint, on port `9443` by default, and gives administrators fine-grained control over remote access. The API key is created on the remote cluster and defines the permissions available to all cross-cluster requests, while local user roles can further restrict, but not extend, those permissions.
    Starting with Elastic Stack 9.3, the API key security model also supports [strong identity verification](/elastic/docs-content/pull/5592/deploy-manage/remote-clusters/security-models#remote-cluster-strong-verification), adding an extra layer of security. With this feature, the API key can be restricted to only be usable by requests that present an allowed certificate identity, which the remote cluster validates during authentication.
  </definition>
  <definition term="TLS certificate (deprecated in Elastic Stack 9.0.0)">
    This model uses mutual TLS authentication over the Elasticsearch transport interface for cross-cluster operations. User authentication is performed on the local cluster and a user's role names are passed to the remote cluster for authorization. Because a superuser on the local cluster automatically gains full read access to the remote cluster, this model is only suitable for clusters within the same security domain.
  </definition>
</definitions>


## Setup

Based on the selected security model, use one of the following setup procedures.
<tab-set>
  <tab-item title="API key">
    Follow these steps to configure the [API key security model](/elastic/docs-content/pull/5592/deploy-manage/remote-clusters/security-models#api-key) for remote clusters. If you run into any issues, refer to [Troubleshooting](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/5592/troubleshoot/elasticsearch/remote-clusters).

    ### Enable the remote cluster server interface on the remote cluster

    By default, the remote cluster server interface is not enabled on ECK-managed clusters. To use the API key–based security model for cross-cluster connections, you must first enable it on the remote Elasticsearch cluster by setting `spec.remoteClusterServer.enabled: true`:
    ```yaml
    apiVersion: elasticsearch.k8s.elastic.co/v1
    kind: Elasticsearch
    metadata:
      name: <cluster-name>
      namespace: <namespace>
    spec:
      version: 9.3.2
      remoteClusterServer:
        enabled: true
      nodeSets:
        - name: default
          count: 3
          ...
          ...
    ```

    <note>
      Enabling the remote cluster server triggers a restart of the Elasticsearch cluster.
    </note>


    ### Configure the local clusterOnce the remote cluster server is enabled and running on the remote cluster, you can configure the Elasticsearch reference on the local cluster and include the desired permissions for cross-cluster search and cross-cluster replication under the `spec.remoteClusters` field.
    Permissions have to be included under the `apiKey` field. The API model of the Elasticsearch resource is compatible with the [Elasticsearch cross-cluster API key API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-security-create-cross-cluster-api-key) model. Fine-grained permissions can therefore be configured in both the `search` and `replication` fields.The following example shows how to connect a local cluster to a remote cluster and specify the cross-cluster permissions under the `apiKey` field. This configuration is applied to the local cluster manifest:
    ```yaml
    apiVersion: elasticsearch.k8s.elastic.co/v1
    kind: Elasticsearch
    metadata:
      name: <local-cluster-name>
      namespace: <ns-local>
    spec:
      version: 9.3.2
      remoteClusters:
      - name: <remote-cluster-name>
        elasticsearchRef:
          name: <remote-cluster-name> 
          namespace: <ns-remote> 
        apiKey:
          access:
            search:
              names:
                - kibana_sample_data_ecommerce  
            replication:
              names:
                - kibana_sample_data_ecommerce  
      nodeSets:
      - count: 3
        name: default
      ...
      ...
    ```
    You can find a complete example in the [Elastic Cloud on Kubernetes repository's recipes directory](https://github.com/elastic/cloud-on-k8s/tree/3.3/config/recipes/remoteclusters).
  </tab-item>

  <tab-item title="TLS certificate (deprecated)">
    The following example shows how to connect a local cluster to a remote cluster using the certificate-based security model. The configuration is applied to the local cluster manifest:
    ```yaml
    apiVersion: elasticsearch.k8s.elastic.co/v1
    kind: Elasticsearch
    metadata:
      name: <local-cluster-name>
      namespace: <ns-local>
    spec:
      version: 8.16.1
      remoteClusters:
      - name: <remote-cluster-name>
        elasticsearchRef:
          name: <remote-cluster-name> 
          namespace: <ns-remote> 
      nodeSets:
      - count: 3
        name: default
      ...
      ...
    ```
  </tab-item>
</tab-set>


## Configure roles and users

If you're using the API key–based security model for cross-cluster replication or cross-cluster search, you can define user roles with [remote indices privileges](/elastic/docs-content/pull/5592/deploy-manage/users-roles/cluster-or-deployment-auth/role-structure#roles-remote-indices-priv) on the local cluster to further restrict the permissions granted by the API key. For more details, refer to [Configure roles and users](/elastic/docs-content/pull/5592/deploy-manage/remote-clusters/remote-clusters-api-key#remote-clusters-privileges-api-key).