[Enhancement]: EKS should support 100.64.0.0/10 and 198.19.0.0/16

[taliesins]

Description

EKS supports 100.64.0.0/10 and 198.19.0.0/16 CIDR blocks as per: https://aws.amazon.com/about-aws/whats-new/2018/10/amazon-eks-now-supports-additional-vpc-cidr-blocks/

If you try to use these CIDR blocks you will receive an error

╷
│ Error: invalid value for kubernetes_network_config.0.service_ipv4_cidr (must be within 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16)
│ 
│   with module.eks-cluster.module.eks_blueprints.aws_eks_cluster.this[0],
│   on .terraform/modules/eks-cluster.eks_blueprints/main.tf line 27, in resource "aws_eks_cluster" "this":
│   27: resource "aws_eks_cluster" "this" {
│ 
╵

The validation expression to fix is: https://github.com/hashicorp/terraform-provider-aws/blob/fbad5d3b00f58789b2b70fc6188ea240f1191e49/internal/service/eks/cluster.go#L191C8-L191C168

In big organizations that have grown through aquisitions, they tend to have a very fragmented ip spaces. So it would be great if we could make use of this extra ip space.

Affected Resource(s) and/or Data Source(s)

aws_eks_cluster

Potential Terraform Configuration

No response

References

No response

Would you like to implement a fix?

None

[github-actions[bot]]

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[acwwat]

I could be wrong, but It seems that EKS services still need to run within the RFC 1918 private IP range (as required by the CreateCluster API), but worker nodes can leverage the extended range using CNI custom networking. This blog post provides a Terraform example for such a setup.