Amazon EKS service IP addresses

The EKS cluster control plane IP addresses will vary depending on the configuration of the VPC and Subnets where the EKS cluster is configured. The cluster will configure one ENI in each selected subnet, consuming one IP address from the subnet's configured CIDR block. You can view these ENIs from the AWS Management Console, in the EC2 Dashboard, under the Network interfaces section. Keep in mind, that these IP addresses may change due to the cluster upgrades.

Kubernetes assigns a stable, reliable IP address to each newly created service from the cluster's pool of available service IP addresses. Previously, Amazon EKS automatically chose a value for this range based on the primary CIDR block of the Amazon VPC used by the cluster. While this worked for most cases, customers with VPCs peered to on-premise networks or other Amazon VPCs found that the EKS chosen Kubernetes service IP address range may conflict with other IP ranges in use across their network. This resulted in pods being unable to communicate with certain applications that reside on peered networks external to the cluster. Now, EKS users can configure the Kubernetes service IP address range on cluster creation. Customers who operate clusters in a peered or direct connected network environment can ensure pods are able to communicate with external services available across their networks.

If you want to specify which IPv4 Classless Inter-domain Routing (CIDR) block Kubernetes assigns service IP addresses from, specify the serviceIPv4CIDR option.

You can only specify this option when using the IPv4 address family and only at cluster creation. If you don't specify this, then Kubernetes assigns service IP addresses from either the 10.100.0.0/16 or 172.20.0.0/16 CIDR blocks.

https://aws.amazon.com/about-aws/whats-new/2020/10/amazon-eks-supports-configurable-kubernetes-service-ip-address-range/ https://docs.aws.amazon.com/eks/latest/userguide/create-cluster.html