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VPC Configuration

Change VPC CIDR

If you need to set up peering with another VPC, or simply need a larger or smaller range of IPs, you can use --vpc-cidr flag to change it. Please refer to the AWS docs for guides on choosing CIDR blocks which are permitted for use in an AWS VPC.

If you are creating an IPv6 cluster you can also bring your own IPv6 pool by configuring VPC.IPv6Cidr and VPC.IPv6Pool. See AWS docs on how to import your own pool.

Use an existing VPC: shared with kops

You can use the VPC of an existing Kubernetes cluster managed by kops. This feature is provided to facilitate migration and/or cluster peering.

If you have previously created a cluster with kops, e.g. using commands similar to this:

export KOPS_STATE_STORE=s3://kops
kops create cluster cluster-1.k8s.local --zones=us-west-2c,us-west-2b,us-west-2a --networking=weave --yes

You can create an EKS cluster in the same AZs using the same VPC subnets (NOTE: at least 2 AZs/subnets are required):

eksctl create cluster --name=cluster-2 --region=us-west-2 --vpc-from-kops-cluster=cluster-1.k8s.local

Use existing VPC: other custom configuration

eksctl provides some, but not complete, flexibility for custom VPC and subnet topologies.

You can use an existing VPC by supplying private and/or public subnets using the --vpc-private-subnets and --vpc-public-subnets flags. It is up to you to ensure the subnets you use are categorised correctly, as there is no simple way to verify whether a subnet is actually private or public, because configurations vary.

Given these flags, eksctl create cluster will determine the VPC ID automatically, but it will not create any routing tables or other resources, such as internet/NAT gateways. It will, however, create dedicated security groups for the initial nodegroup and the control plane.

You must ensure to provide at least 2 subnets in different AZs. There are other requirements that you will need to follow (listed below), but it's entirely up to you to address those. (For example, tagging is not strictly necessary, tests have shown that it is possible to create a functional cluster without any tags set on the subnets, however there is no guarantee that this will always hold and tagging is recommended.)

Standard requirements:

  • all given subnets must be in the same VPC, within the same block of IPs
  • a sufficient number IP addresses are available, based on needs
  • sufficient number of subnets (minimum 2), based on needs
  • subnets are tagged with at least the following:
    • kubernetes.io/cluster/<name> tag set to either shared or owned
    • kubernetes.io/role/internal-elb tag set to 1 for private subnets
    • kubernetes.io/role/elb tag set to 1 for public subnets
  • correctly configured internet and/or NAT gateways
  • routing tables have correct entries and the network is functional
  • NEW: all public subnets should have the property MapPublicIpOnLaunch enabled (i.e. Auto-assign public IPv4 address in the AWS console)

There may be other requirements imposed by EKS or Kubernetes, and it is entirely up to you to stay up-to-date on any requirements and/or recommendations, and implement those as needed/possible.

Default security group settings applied by eksctl may or may not be sufficient for sharing access with resources in other security groups. If you wish to modify the ingress/egress rules of the security groups, you might need to use another tool to automate changes, or do it via EC2 console.

When in doubt, don't use a custom VPC. Using eksctl create cluster without any --vpc-* flags will always configure the cluster with a fully-functional dedicated VPC.

Examples

Create a cluster using a custom VPC with 2x private and 2x public subnets:

eksctl create cluster \
  --vpc-private-subnets=subnet-0ff156e0c4a6d300c,subnet-0426fb4a607393184 \
  --vpc-public-subnets=subnet-0153e560b3129a696,subnet-009fa0199ec203c37

or use the following equivalent config file:

apiVersion: eksctl.io/v1alpha5
kind: ClusterConfig

metadata:
  name: my-test
  region: us-west-2

vpc:
  id: "vpc-11111"
  subnets:
    private:
      us-west-2a:
          id: "subnet-0ff156e0c4a6d300c"
      us-west-2c:
          id: "subnet-0426fb4a607393184"
    public:
      us-west-2a:
          id: "subnet-0153e560b3129a696"
      us-west-2c:
          id: "subnet-009fa0199ec203c37"

nodeGroups:
  - name: ng-1

Create a cluster using a custom VPC with 3x private subnets and make initial nodegroup use those subnets:

eksctl create cluster \
  --vpc-private-subnets=subnet-0ff156e0c4a6d300c,subnet-0549cdab573695c03,subnet-0426fb4a607393184 \
  --node-private-networking

or use the following equivalent config file:

apiVersion: eksctl.io/v1alpha5
kind: ClusterConfig

metadata:
  name: my-test
  region: us-west-2

vpc:
  id: "vpc-11111"
  subnets:
    private:
      us-west-2d:
          id: "subnet-0ff156e0c4a6d300c"
      us-west-2c:
          id: "subnet-0549cdab573695c03"
      us-west-2a:
          id: "subnet-0426fb4a607393184"

nodeGroups:
  - name: ng-1
    privateNetworking: true

Create a cluster using a custom VPC 4x public subnets:

eksctl create cluster \
  --vpc-public-subnets=subnet-0153e560b3129a696,subnet-0cc9c5aebe75083fd,subnet-009fa0199ec203c37,subnet-018fa0176ba320e45
apiVersion: eksctl.io/v1alpha5
kind: ClusterConfig

metadata:
  name: my-test
  region: us-west-2

vpc:
  id: "vpc-11111"
  subnets:
    public:
      us-west-2d:
          id: "subnet-0153e560b3129a696"
      us-west-2c:
          id: "subnet-0cc9c5aebe75083fd"
      us-west-2a:
          id: "subnet-009fa0199ec203c37"
      us-west-2b:
          id: "subnet-018fa0176ba320e45"

nodeGroups:
  - name: ng-1

More examples can be found in the repo's examples folder:

Custom Shared Node Security Group

eksctl will create and manage a shared node security group that allows communication between unmanaged nodes and the cluster control plane and managed nodes.

If you wish to provide your own custom security group instead, you may override the sharedNodeSecurityGroup field in the config file:

vpc:
  sharedNodeSecurityGroup: sg-0123456789

By default, when creating the cluster, eksctl will add rules to this security group to allow communication to and from the default cluster security group that EKS creates. The default cluster security group is used by both the EKS control plane and managed node groups.

If you wish to manage the security group rules yourself, you may prevent eksctl from creating the rules by setting manageSharedNodeSecurityGroupRules to false in the config file:

vpc:
  sharedNodeSecurityGroup: sg-0123456789
  manageSharedNodeSecurityGroupRules: false

NAT Gateway

The NAT Gateway for a cluster can be configured to be Disabled, Single (default) or HighlyAvailable. The HighlyAvailable option will deploy a NAT Gateway in each Availability Zone of the Region, so that if an AZ is down, nodes in the other AZs will still be able to communicate to the Internet.

It can be specified through the --vpc-nat-mode CLI flag or in the cluster config file like the example below:

vpc:
  nat:
    gateway: HighlyAvailable # other options: Disable, Single (default)

See the complete example here.

Note: Specifying the NAT Gateway is only supported during cluster creation. It isn't touched during a cluster upgrade. There are plans to support changing between different modes on cluster update in the future.