awslabs/amazon-eks-ami

Description of NodeConfig `.spec.cluster.cidr` is misleading

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What happened:

The documentation says:

cidr string | CIDR is your cluster's Pod IP CIDR. This value is used to infer your cluster's DNS address.

...but it actually seems to expect the so-called "Service IPv4 range" (at least for a simple ipv4 cluster) - that is the CIDR in which the EKS DNS service lives. This is not the CIDR from which the pods get their IP addresses, so using the "Pod IP" phrase is very misleading.

In our case the "Service IPv4 range" is 172.* while the Pods receive their IP addresses from the VPC subnets of the worker nodes, which are 10.*.

What you expected to happen:

Documentation should be unambiguous. At the very least it should point out exactly where the relevant value is inside the aws eks describe-cluster --name <name> output, not just the generic sentence:

These details can be found using the DescribeCluster API.

If I'm right, the unambiguous way to obtain the CIDR value is aws eks describe-cluster --name <name> --query cluster.kubernetesNetworkConfig.serviceIpv4Cidr (for IPv4 at least).

How to reproduce it (as minimally and precisely as possible): n/a

Anything else we need to know?: n/a

Environment:

  • AWS Region: us-east-1
  • Instance Type(s): mixed
  • EKS Platform version (use aws eks describe-cluster --name <name> --query cluster.platformVersion): eks.19
  • Kubernetes version (use aws eks describe-cluster --name <name> --query cluster.version): 1.25
  • AMI Version: amazon-eks-node-al2023-x86_64-standard-1.25-v20240522