Pod Networking

When creating a EKS cluster the Amazon VPC CNI will be used by default for Pod Networking.

When using the AWS Console to create an EKS cluster with a Kubernetes version of v1.18 or greater you are required to select a specific version of the VPC CNI to use.

Using the VPC CNI Addon

You can use an explicit version of the Amazon VPC CNI by using the vpc-cni EKS addon. See the addons documentation for further details of how to use addons.

Using Custom VPC CNI Configuration

If your use case demands custom networking VPC CNI configuration you might already be familiar with the helm chart which helps with the process. This gives you access to ENI Configs and you can set Environment Variables on the aws-node DaemonSet where the VPC CNI runs. CAPA is able to tune the same DaemonSet through Kubernetes.

The following example shows how to turn on custom network config and set a label definition.

kind: AWSManagedControlPlane
apiVersion: controlplane.cluster.x-k8s.io/v1beta1
metadata:
  name: "capi-managed-test-control-plane"
spec:
  vpcCni:
    env:
    - name: AWS_VPC_K8S_CNI_CUSTOM_NETWORK_CFG
      value: "true" 
    - name: ENABLE_PREFIX_DELEGATION
      value: "true"

Increase node pod limit

You can increase the pod limit per-node as per the upstream AWS documentation. You’ll need to enable the vpc-cni plugin addon on your EKS cluster as well as enable prefix assignment mode through the ENABLE_PREFIX_DELEGATION environment variable.

kind: AWSManagedControlPlane
apiVersion: controlplane.cluster.x-k8s.io/v1beta1
metadata:
  name: "capi-managed-test-control-plane"
spec:
  vpcCni:
    env:
    - name: AWS_VPC_K8S_CNI_CUSTOM_NETWORK_CFG
      value: "true" 
    - name: ENABLE_PREFIX_DELEGATION
      value: "true"
  addons:
  - name: vpc-cni
    version: <replace_with_version>
    conflictResolution: overwrite
  associateOIDCProvider: true
  disableVPCCNI: false

Using Secondary CIDRs

EKS allows users to assign a secondary CIDR range for pods to be assigned. Below are how to get CAPA to generate ENIConfigs in both the managed and unmanaged VPC configurations.

Secondary CIDR functionality will not work unless you enable custom network config too.

Managed (dynamic) VPC

Default configuration for CAPA is to manage the VPC and all the subnets for you dynamically. It will create and delete them along with your cluster. In this method all you need to do is set a SecondaryCidrBlock to one of the allowed two IPv4 CIDR blocks: 100.64.0.0/10 and 198.19.0.0/16. CAPA will automatically generate subnets and ENIConfigs for you and the VPC CNI will do the rest.

kind: AWSManagedControlPlane
apiVersion: controlplane.cluster.x-k8s.io/v1beta1
metadata:
  name: "capi-managed-test-control-plane"
spec:
  secondaryCidrBlock: 100.64.0.0/10
  vpcCni:
    env:
    - name: AWS_VPC_K8S_CNI_CUSTOM_NETWORK_CFG
      value: "true"

Unmanaged (static) VPC

In an unmanaged VPC configuration CAPA will create no VPC or subnets and will instead assign the cluster pieces to the IDs you pass. In order to get ENIConfigs to generate you will need to add tags to the subnet you created and want to use as the secondary subnets for your pods. This is done through tagging the subnets with the following tag: sigs.k8s.io/cluster-api-provider-aws/association=secondary.

Setting SecondaryCidrBlock in this configuration will be ignored and no subnets are created.

Using an alternative CNI

There may be scenarios where you do not want to use the Amazon VPC CNI. EKS supports a number of alternative CNIs such as Calico, Cilium, and Weave Net (see docs for full list).

There are a number of ways to install an alternative CNI into the cluster. One option is to use a ClusterResourceSet to apply the required artifacts to a newly provisioned cluster.

When using an alternative CNI you will want to delete the Amazon VPC CNI, especially for a cluster using v1.17 or less. This can be done via the disableVPCCNI property of the AWSManagedControlPlane:

kind: AWSManagedControlPlane
apiVersion: controlplane.cluster.x-k8s.io/v1beta1
metadata:
  name: "capi-managed-test-control-plane"
spec:
  region: "eu-west-2"
  sshKeyName: "capi-management"
  version: "v1.18.0"
  disableVPCCNI: true

You cannot set disableVPCCNI to true if you are using the VPC CNI addon.

Some alternative CNIs provide for the replacement of kube-proxy, such as in Calico and Cilium. When enabling the kube-proxy alternative, the kube-proxy installed by EKS must be deleted. This can be done via the disable property of kubeProxy in AWSManagedControlPlane:

kind: AWSManagedControlPlane
apiVersion: controlplane.cluster.x-k8s.io/v1beta1
metadata:
  name: "capi-managed-test-control-plane"
spec:
  region: "eu-west-2"
  sshKeyName: "capi-management"
  version: "v1.18.0"
  disableVPCCNI: true
  kubeProxy:
    disable: true

You cannot set disable to true in kubeProxy if you are using the kube-proxy addon.

Additional Information

See the AWS documentation for further details of EKS pod networking.

Kubernetes Cluster API Provider AWS