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This topic describes the security group requirements of an Amazon EKS cluster.

Architecture

The cluster security group is a unified security group that is used to control communications between the Kubernetes control plane and compute resources on the cluster. The cluster security group is applied by default to the Kubernetes control plane managed by Amazon EKS as well as any managed compute resources created through the Amazon EKS API.

When you create a cluster, Amazon EKS creates a cluster security group that's named eks-cluster-sg-<EKS-cluster-ID>. This security group has the following default rules:

Rule type	Protocol	Ports	Source	Destination	Rule Category
Inbound	All	All	Self	N/A	Default rule
Outbound	All	All	N/A	0.0.0.0/0	Default rule

The additional cluster security groups control communications from the Kubernetes control plane to compute resources.
This security group allows port 443 inbound from the worker node SG, so that the kubelets could communicate with the Kubernetes API server.
It also includes port 10250 for outbound traffic to the worker node SG; 10250 is the port that the kubelets listen on.

Rule type	Protocol	Ports	Source	Destination	Rule Category
Inbound	TCP	443	Worker node SG	N/A	Minimum rule
Outbound	TCP	10250	N/A	Worker node SG	Minimum rule
Outbound	TCP	8443	N/A	Worker node SG	Knative web hook

The worker node security groups are security groups applied to unmanaged worker nodes that control communications from worker nodes to the Kubernetes control plane.

The node group rules allow port 10250 inbound from the control plane SG and 443 outbound to the control plane SG. 

Rule type	Protocol	Ports	Source	Destination	Rule Category
Inbound	ICMP (for IPv4) - Destination Unreachable	fragmentation required, and DF flag set	Self	N/A	Recommended rule
Inbound	TCP	Instance listener	ALB SG	N/A	ALB and TG required rule
Inbound	TCP	Health check	ALB SG	N/A	ALB and TG required rule
Inbound	TCP	Instance listener and health check	NLB SG	N/A	NLB and TG required rule
Inbound	All	All	Self	N/A	Minimum rule
Inbound	TCP	10250	Additional cluster SG	N/A	Minimum rule
Inbound	TCP	443	Additional cluster SG	N/A	Known requirements: - Istio (refer to below "Ports used by Istio" section)
Inbound	TCP	8443	Additional cluster SG	N/A	Knative web hook
Outbound	All	All	N/A	0.0.0.0/0	Default rule

Ports used by Istio

The following ports and protocols are used by the Istio sidecar proxy (Envoy).

To avoid port conflicts with sidecars, applications should not use any of the ports used by Envoy.

Port	Protocol	Description	Pod-internal only	Status
15000	TCP	Envoy admin port (commands/diagnostics)	Yes
15001	TCP	Envoy outbound	No
15004	HTTP	Debug port	Yes
15006	TCP	Envoy inbound	No
15008	H2	HBONE mTLS tunnel port	No
15009	H2C	HBONE port for secure networks	No
15020	HTTP	Merged Prometheus telemetry from Istio agent, Envoy, and application	No
15021	HTTP	Health checks	No
15053	DNS	DNS port, if capture is enabled	Yes
15090	HTTP	Envoy Prometheus telemetry	No

The following ports and protocols are used by the Istio control plane (istiod).

Port	Protocol	Description	Local host only	Status
443	HTTPS	Webhooks service port	No	Applied
8080	HTTP	Debug interface (deprecated, container port only)	No	N/A
15010	GRPC	XDS and CA services (Plaintext, only for secure networks)	No
15012	GRPC	XDS and CA services (TLS and mTLS, recommended for production use)	No
15014	HTTP	Control plane monitoring	No
15017	HTTPS	Webhook container port, forwarded from 443	No	Applied

References

Amazon EKS security group requirements and considerations

Network security

Application Requirements

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