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Docs on creating an EKS setup with Secondary CIDR block for Pod IP addresses. Includes Karpenter configuration.

This repo uses eksdemo to create an EKS Cluster and install karpenter.

Complete Demo: AWS VPC CNI Custom Networking

  • Creates an EKS Cluster with a VPC with Secondary CIDR block.
    • Secondary CIDR block is a VPC feature that allows you to add additional IP addresses to your VPC.
    • We will to use the secondary CIDR block for the pods, and the primary CIDR block of the VPC for the nodes.
  • Creates 3 Private subnets in the Secondary CIDR block with /19 mask, so we can have available IP count of 3*8190=24570 for our pods.
  • Updates aws-node with Custom Networking configuration.
  • Creates ENIConfig for each of our subnets in the Secondary CIDR block.
  • Creates Karpenter Provisioner and AWSNodeTemplate.
  • Offers troubleshooting steps for common issues.
  • Recommends how to choose EC2 Instance Types.


Why CNI Custom Networking this needed?

  • Running many nodes in EKS can cause IP address exhaustion in the VPC.
  • How many IP addresses are available to a node is determined by nodes ENI capacity.
    • Because of this, EKS requires running many nodes to keep up with the Pod count.
  • Using a VPC with Secondary CIDR block allows us to have more IP addresses available to our pods.
  • Karpenter is a faster option for cluster autoscaling than the default EKS Cluster Autoscaler.
  • Karpenter can be configured to use Spot Instances, which can save a lot of money.

CNI Config Diagram

AWS CNI and ENIConfig Diagram


Example Karpenter v1alpha configuration. Includes demo: EKS Custom Networking with Secondary CIDR block for Pod IP addresses.








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