Cluster Linking with Private Networking¶

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Supported Cluster Combinations¶

Cluster Linking is fundamentally a networking feature: it copies data over the network. As such, Cluster Linking requires that at least one of the clusters involved has connectivity to the other cluster. Therefore, the networking situation of each cluster determines whether the two clusters can be linked, and whether the destination cluster or the source cluster must initiate the connection. By default, the destination cluster will initiate the connection. A special mode called “source-initiated links” allows the source cluster to initiate the connection of the cluster link.

The following tables show which networking combinations are possible, and whether a source-initiated link is required.

Tip

When using the Confluent Cloud Console to create cluster links, only linkable clusters are shown in the drop-down options. Clusters that cannot be linked are filtered out.

Confluent Cloud Source and Destination Clusters¶

Source cluster	Destination cluster	Possible?	Notes
Confluent Cloud - A Basic or Standard cluster, or a Dedicated [1] cluster with Internet networking	Confluent Cloud - Any Dedicated cluster	Yes
Confluent Cloud - A cluster with private networking	Confluent Cloud - A Dedicated cluster in the same Confluent Cloud network	Yes
Confluent Cloud - A Dedicated cluster with Transit Gateway networking	Confluent Cloud - A Dedicated cluster with Transit Gateway networking	Yes (in Preview) [2]	Contact Confluent Support or your Confluent Account Team Requires proper Transit Gateway configuration Neither cluster can use the CIDR 198.18.0.0/15
Confluent Cloud - A cluster with private networking	Confluent Cloud - A cluster with private networking in a different Confluent Cloud network	No (except the Transit Gateway case above)
Confluent Cloud - A cluster with private networking	Confluent Cloud - A Dedicated cluster with public networking	Yes (in Preview) [2]	Must use a source-initiated link

[1]	Basic, Standard, and Dedicated cluster types are described in Supported Cluster Types.

[2]	(1, 2, 3, 4) Preview scenarios are for testing and evaluation purposes or to give feedback to Confluent. They are not suitable for production use cases and do not fall into any Confluent Support SLAs.

Confluent Platform and Confluent Cloud¶

Source cluster	Destination cluster	Possible?	Notes
Confluent Platform 7.1.0 or later	Confluent Cloud - Any Dedicated cluster	Yes	Must use a source-initiated link Source Confluent Platform cluster must have connectivity to the destination cluster Brokers must be Confluent Server
Confluent Platform 5.4 to 7.0 with public endpoints on all brokers	Confluent Cloud - Any Dedicated cluster	Yes	If the Confluent Cloud cluster has static egress IPs, a firewall in front of Confluent Platform can filter on those IPs Cluster link must use SASL/PLAIN, SASL/SCRAM, and/or mTLS
Confluent Platform 5.4 to 7.0 without public endpoints	Confluent Cloud - A Dedicated cluster with private networking (all networking types)	Yes (in Preview) [2]	Contact Confluent Support or your Confluent Account Team Destination Confluent Cloud cluster must have connectivity to the source Confluent Cloud cluster Cluster link must use SASL/PLAIN, SASL/SCRAM, and/or mTLS
Confluent Cloud - A Basic or Standard cluster, or a Dedicated cluster with Internet networking	Confluent Platform 7.0.0 or later	Yes
Confluent Cloud - A cluster with private networking	Confluent Platform 7.0.0 or later	Yes	Destination Confluent Cloud cluster must have connectivity to the source Confluent Cloud cluster

Confluent Cloud and Apache Kafka®¶

Source cluster	Destination cluster	Possible?	Notes
Kafka 2.4 or later with public endpoints on all brokers	Confluent Cloud - Any Dedicated cluster	Yes	If the Confluent Cloud cluster has static egress IPs, a firewall in front of Kafka can filter on those IPs Cluster link must use SASL/PLAIN, SASL/SCRAM, and/or mTLS
Kafka 2.4 or later without public endpoints	Confluent Cloud - A Dedicated cluster with private networking (all networking types)	Yes (in Preview) [2]	Contact Confluent Support or your Confluent Account Team Destination Confluent Cloud cluster must have connectivity to the source Kafka cluster

Diagrams of Supported Combinations for Private Networking¶

Confluent Cloud to Confluent Cloud¶

../../_images/cluster-link-private-net-cloud-to-cloud.png

Confluent Cloud to Confluent Platform/Apache Kafka®¶

../../_images/cluster-link-private-net-cloud-to-cp-kafka.png

How to use Cluster Links with Private Networking¶

Using the Confluent Cloud Console for Cluster Linking with Private Networking¶

To view, create, and modify cluster links and mirror topics in the Confluent Cloud Console, the cluster link’s destination cluster must be accessible from your browser. If your destination cluster is a Confluent Cloud cluster with private networking, you must have completed the setup described in Access Confluent Cloud Console with Private Networking.

If your browser cannot access the destination cluster, you will not see any cluster links on that cluster, nor an indication of which topics are mirror topics. You will not be able to create a cluster link with that cluster as its destination cluster.

If your source cluster is also a Confluent Cloud cluster with private networking, then some features of the Confluent Cloud Console require your browser to be able to reach your source cluster, also:

Creating a “Confluent Cloud to Confluent Cloud” cluster link as an OrgAdmin, which creates ACLs and an API key on the source cluster.
Viewing the source cluster topics’ throughput metric on a cluster link
Using the drop-down menu of source cluster topic names to create a mirror topic. Topic names must be entered manually.

When creating a cluster link in the Confluent Cloud Console, rest assured that the drop-down menus automatically filter for source clusters and destination clusters that can be linked. If you see a drop-down option for the cluster, then a cluster link is possible and generally available. Preview cases are excluded from the drop-downs, and require using the Confluent CLI or the Confluent Cloud REST API to create a cluster link.

Running Cluster Linking API and CLI Commands with Private Networking¶

Cluster Linking commands require that the location where you are running them has access to the destination cluster of the cluster link:

Creating, updating, listing, describing, and deleting cluster links
Creating, listing, and describing mirror topics

For example, when running the Confluent CLI command, the shell must have access to the destination cluster. If your destination cluster has private networking, one way to achieve this is to SSH into a virtual machine that has network connectivity (by means of Privatelink, Transit Gateway, or Peering) to the destination cluster.

Managing Cluster Links with Private Networking¶

Aside from the above mentioned requirements, the user experience when using a cluster link with private networking is the same as when using a cluster link with public networking. The same commands work in the same ways. That means you can follow the same Cluster Linking tutorials using the same steps, regardless of whether your clusters use public or private networking.

Exception: When Cluster Linking from a cluster with private networking to a cluster with public networking (currently in Preview), a source-initiated link is required. This introduces different configurations and an extra step.

Confluent Cloud Billing Considerations¶

There are cost differences associated with private vs. public networking. These are detailed under Cluster Linking in the Billing documentation. Examples are provided there for public networking, with more details about private networking to follow soon.