Submariner is an open-source, CNCF sandbox project designed to enable seamless and direct networking between Kubernetes clusters, whether they are hosted on-premises or in the cloud.

The main features of this tool include:

• Direct Multi-Cluster Networking: It allows for direct communication between Pods and Services located in different Kubernetes clusters.

• Cross-Cluster L3 Connectivity: Submariner provides Layer 3 connectivity across clusters, supporting both encrypted and unencrypted connections.

• Global Service Discovery: It enables services to be discovered across multiple clusters, allowing applications to span different cloud providers, regions, and data centers for enhanced geo-redundancy, scale, and fault isolation.

• CNI Agnosticism: The tool is designed to be completely independent of the specific network plugin (CNI) used by the clusters.

• Overlapping CIDR Support: Through its Globalnet Controller, Submariner can interconnect clusters even if they have overlapping IP address ranges.

• Modular Architecture: Its architecture includes specialized components such as a Broker for state synchronization, a Gateway Engine for cross-cluster traffic, and a Route Agent.

• Simplified Management: It features a dedicated command-line utility called subctl to streamline deployment and management tasks.

• Broad Compatibility: It offers quickstart guides for various environments including GKE, Rancher, and OpenShift on platforms like AWS, Azure, and GCP.