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How to Add Instances to a Cluster

Updated on 21 April, 2026

Add existing instances to a Vultr cluster in bulk or individually. GPU clusters automatically configure fabric networking when instances join.

Adding instances to a cluster associates existing instances with the cluster and configures the fabric networking automatically. For GPU clusters, the high-performance interconnect (RoCE or InfiniBand) is provisioned when instances join — no manual VLAN or PKey setup is needed. You can add a single instance or multiple instances at once.

Note
An instance can belong to only one cluster at a time. All instances in a cluster must be in the same region and match the cluster's plan type.

This guide explains how to add instances to a cluster using the Vultr API.

  1. Send a GET request to the List Clusters endpoint to retrieve all clusters.

    console 
    $ curl "https://api.vultr.com/v2/clusters" \
    -X GET \
    -H "Authorization: Bearer ${VULTR_API_KEY}"

    Note the id of the cluster to which you want to add instances.

  2. Send a GET request to the List Instances endpoint to retrieve all instances.

    console 
    $ curl "https://api.vultr.com/v2/instances" \
    -X GET \
    -H "Authorization: Bearer ${VULTR_API_KEY}"

    Note the id of the instance(s) you want to add to the cluster.

Add Multiple Instances

  1. Send a POST request to the Bulk Add Instances endpoint to add multiple instances to the cluster. Replace {cluster-id} with the cluster id and provide the instance IDs in the instances array. Set action to add.

    console 
    $ curl "https://api.vultr.com/v2/clusters/{cluster-id}" \
    -X POST \
    -H "Authorization: Bearer ${VULTR_API_KEY}" \
    -H "Content-Type: application/json" \
    -d '{
        "action": "add",
        "instances": [
            "INSTANCE-ID-1",
            "INSTANCE-ID-2"
        ]
    }'

    A successful request returns an HTTP 202 Accepted response.

  2. Send a GET request to the Get Cluster endpoint to retrieve the cluster details. Replace {cluster-id} with the cluster id.

    console 
    $ curl "https://api.vultr.com/v2/clusters/{cluster-id}" \
    -X GET \
    -H "Authorization: Bearer ${VULTR_API_KEY}"

    Verify that the added instances appear in the cluster's instance list.

Add a Single Instance

  1. Send a POST request to the Add Single Instance endpoint to add a single instance to the cluster. Replace {cluster-id} with the cluster id and {instance-id} with the instance id.

    console 
    $ curl "https://api.vultr.com/v2/clusters/{cluster-id}/add/{instance-id}" \
    -X POST \
    -H "Authorization: Bearer ${VULTR_API_KEY}"

    A successful request returns an HTTP 202 Accepted response.

  2. Send a GET request to the Get Cluster endpoint to retrieve the cluster details.

    console 
    $ curl "https://api.vultr.com/v2/clusters/{cluster-id}" \
    -X GET \
    -H "Authorization: Bearer ${VULTR_API_KEY}"

    Verify that the instance appears in the cluster's instance list.

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