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Antrea Multi-cluster with NetworkPolicy Only Mode

Multi-cluster Gateway works with Antrea networkPolicyOnly mode, in which cross-cluster traffic is routed by Multi-cluster Gateways of member clusters, and the traffic goes through Antrea overlay tunnels between Gateways and local cluster Pods. Pod traffic within a cluster is still handled by the primary CNI, not Antrea.

Deploying Antrea in `networkPolicyOnly` mode with Multi-cluster feature

This section describes steps to deploy Antrea in networkPolicyOnly mode with the Multi-cluster feature enabled on an EKS cluster.

You can follow the EKS documentation to create an EKS cluster, and follow the Antrea EKS installation guide to deploy Antrea to an EKS cluster. Please note there are a few changes required by Antrea Multi-cluster. You should set the following configuration parameters in antrea-agent.conf of the Antrea deployment manifest to enable the Multicluster feature and Antrea Multi-cluster Gateway:

kind: ConfigMap
apiVersion: v1
metadata:
 name: antrea-config
 namespace: kube-system
data:
 antrea-agent.conf: |
   featureGates:
     Multicluster: true
   multicluster:
     enableGateway: true
     namespace: "" # Change to the Namespace where antrea-mc-controller is deployed.

Repeat the same steps to deploy Antrea for all member clusters in a ClusterSet. Besides the Antrea deployment, you also need to deploy Antrea Multi-cluster Controller in each member cluster. Make sure the Service CIDRs (ClusterIP ranges) must not overlap among the member clusters. Please refer to the quick start guide or the user guide to learn more information about how to configure a ClusterSet.

Connectivity between Clusters

When EKS clusters of a ClusterSet are in different VPCs, you may need to enable connectivity between VPCs to support Multi-cluster traffic. You can check the following steps to set up VPC connectivity for a ClusterSet.

In the following descriptions, we take a ClusterSet with two member clusters in two VPCs as an example to describe the VPC configuration.

Cluster ID	PodCIDR	Gateway IP
west-cluster	110.13.0.0/16	110.13.26.12
east-cluster	110.14.0.0/16	110.14.18.50

VPC Peering Configuration

When the Gateway Nodes do not have public IPs, you may create a VPC peering connection between the two VPCs for the Gateways to reach each other. You can follow the AWS documentation to configure VPC peering.

You also need to add a route to the route tables of the Gateway Nodes' subnets, to enable routing across the peering connection. For west-cluster, the route should have east-cluster’s Pod CIDR: 110.14.0.0/16 to be the destination, and the peering connection to be the target; for east-cluster, the route should have west-cluster’s Pod CIDR: 110.13.0.0/16 to be the destination. To learn more about VPC peering routes, please refer to the AWS documentation.

Security Groups

AWS security groups may need to be configured to allow tunnel traffic to Multi-cluster Gateways, especially when the member clusters are in different VPCs. EKS should have already created a security group for each cluster, which should have a description like “EKS created security group applied to ENI that is attached to EKS Control Plane master nodes, as well as any managed workloads.”. You can add a new rule to the security group for Gateway traffic. For west-cluster, add an inbound rule with source to be east-cluster’s Gateway IP 110.14.18.50/32; for east-cluster, the source should be west-cluster’s Gateway IP 110.13.26.12/32.

By default, Multi-cluster Gateway IP should be the InternalIP of the Gateway Node, but you may configure Antrea Multi-cluster to use the Node ExternalIP. Please use the right Node IP address as the Gateway IP in the security group rule.