What causes "EKS CNI plugin error"?

VPC CNI add-on version is incompatible with your Kubernetes cluster version Missing or incorrect IAM permissions on worker node IAM role (lacking CNI policy) Worker nodes cannot reach the EC2 API endpoint or EKS API server endpoint (port 443)

Is the "EKS CNI plugin error" error serious?

Yes. This is a high-severity error that usually blocks work until it is fixed, but the steps above resolve it.

How to fix EKS CNI plugin error in Kubernetes

KubernetesINTERMEDIATEHIGHUpdated Dec 6, 2025· 156 views

The EKS CNI (Container Network Interface) plugin fails to initialize on worker nodes, preventing pods from getting IP addresses and cluster nodes from becoming ready. This typically results from incompatible add-on versions, missing IAM permissions, network connectivity issues, or incorrect network configuration.

Quick fix

Fixes EKS CNI plugin error

# Check installed EKS add-ons via CLI
aws eks describe-addon --cluster-name <cluster-name> --addon-name vpc-cni

Check EKS add-on version compatibility
Verify IAM permissions on worker node role
Check network connectivity to AWS APIs
Verify CNI configuration files and aws-node pod status

kubernetes — error

$# Check installed EKS add-ons via CLI
aws eks describe-addon --cluster-name <cluster-name> --addon-name vpc-cni
EKS CNI plugin error

What this error means

AWS EKS uses the Amazon VPC CNI plugin to assign IP addresses from your VPC to Kubernetes pods. This plugin runs as a DaemonSet (aws-node) on every worker node. When the CNI plugin fails to initialize, the kubelet cannot configure networking for containers, leaving nodes in NotReady status and preventing any pods from running. The error manifests when the plugin cannot load its configuration, reach the AWS API to allocate IP addresses, or when the add-on version does not match your Kubernetes cluster version. This is a fundamental networking issue that blocks cluster operations.

Typical symptoms

Nodes remain in NotReady status after being launched
Pods stuck in Pending state with "NetworkPluginNotReady" error
Error message: "container runtime network not ready: NetworkPluginNotReady"
aws-node DaemonSet pods fail to start or crash immediately
No IP addresses assigned to pods in /var/log/aws-routed-eni/ipamd.log
Worker nodes cannot pull Docker images during initialization
EKS cluster created but nodes never fully join the cluster

Common causes

VPC CNI add-on version is incompatible with your Kubernetes cluster version
Missing or incorrect IAM permissions on worker node IAM role (lacking CNI policy)
Worker nodes cannot reach the EC2 API endpoint or EKS API server endpoint (port 443)
Network configuration files not found in /etc/cni/net.d/ on worker nodes
aws-node pods are not running or are in CrashLoopBackOff state
Insufficient IP addresses available in the subnet for the cluster
Security group or network ACL rules blocking communication between nodes and AWS APIs
Custom launch template overriding VPC CNI requirements or blocking required kubelet options

How to fix "EKS CNI plugin error"

1Check EKS add-on version compatibility

First, verify that your VPC CNI add-on version matches your Kubernetes cluster version. Go to the AWS Management Console and check the installed add-ons:

bash

# Check installed EKS add-ons via CLI
aws eks describe-addon --cluster-name <cluster-name> --addon-name vpc-cni

Ensure the add-on version is compatible. If updating the add-on, use the conflict resolution method "Override" to force the update:

2Verify IAM permissions on worker node role

The worker node IAM role must include the AmazonEKS_CNI_Policy. Attach this managed policy if missing:

bash

# Get the node IAM role
NODE_IAM_ROLE=$(aws ec2 describe-instances --instance-ids <instance-id> --query 'Reservations[0].Instances[0].IamInstanceProfile.Arn' --output text | cut -d'/' -f2)

# Attach the CNI policy
aws iam attach-role-policy --role-name $NODE_IAM_ROLE --policy-arn arn:aws:iam::aws:policy/AmazonEKS_CNI_Policy

If you created the cluster with Terraform or CloudFormation, ensure the node IAM role includes this policy in the configuration.

3Check network connectivity to AWS APIs

Worker nodes must reach both the EKS API server endpoint and the EC2 API endpoint. SSH into a node and verify connectivity:

bash

# SSH into the worker node (requires EC2 permissions)
ssh -i <key-pair> ec2-user@<node-ip>

# Test connectivity to EKS API server
curl -I https://<cluster-api-endpoint>:443

# Test connectivity to EC2 API
curl -I https://ec2.amazonaws.com/

# Check security groups allow outbound 443
aws ec2 describe-security-groups --group-ids <sg-id>

Ensure your network ACLs and security groups allow outbound HTTPS (port 443) traffic.

4Verify CNI configuration files and aws-node pod status

Check if the CNI plugin configuration is properly loaded on the worker node:

bash

# SSH into the worker node
ssh -i <key-pair> ec2-user@<node-ip>

# Check if CNI config directory exists and has files
ls -la /etc/cni/net.d/

# Check aws-node pod logs for errors
kubectl logs -n kube-system -l k8s-app=aws-node --tail=100

# Check plugin logs for IP assignment errors
sudo cat /var/log/aws-routed-eni/ipamd.log | tail -50
sudo cat /var/log/aws-routed-eni/plugin.log | tail -50

If logs show "Failed to reach IMDS" or "Failed to reach API", it indicates network access issues.

5Ensure sufficient IP addresses in your subnet

EKS CNI allocates secondary IP addresses from your subnet. Verify you have enough available IPs:

bash

# Check available IPs in subnet
aws ec2 describe-subnets --subnet-ids <subnet-id> --query 'Subnets[0].AvailableIpAddressCount'

# Calculate required IPs: (number of ENIs per node) * (secondary IPs per ENI - 1)
# Each node typically needs 10-100+ available IPs depending on pod density

If IP space is exhausted, either:
- Add additional subnets to your EKS cluster
- Use prefix delegation to allocate entire /28 blocks instead of individual IPs
- Increase your VPC CIDR block and add new subnets

6Update kubelet configuration if using custom launch template

If your worker nodes use a custom EC2 launch template, verify it does not override kubelet networking configuration:

bash

# Check the user data script in your launch template
aws ec2 describe-launch-template-versions --launch-template-id <template-id> --versions All

The user data must not:
- Set --cni-bin-dir or --cni-conf-dir flags
- Start kubelet before the CNI plugin is ready
- Remove or modify /etc/cni/net.d/ files

If the launch template is causing issues, consider removing it and letting AWS use the default configuration. Then replace affected nodes:

7Drain and replace affected nodes

Once you've addressed the root cause, drain and terminate the problematic nodes so new ones can join with the corrected configuration:

bash

# Drain the node to evict all pods
kubectl drain <node-name> --ignore-daemonsets --delete-emptydir-data

# Terminate the node (if using Auto Scaling Group)
aws autoscaling terminate-instance-in-auto-scaling-group --instance-id <instance-id> --should-decrement-desired-capacity

# The ASG will automatically launch a replacement node
# Wait for it to join and become Ready
kubectl get nodes -w

Verify the new node successfully initialized CNI:

Advanced notes

On Bottlerocket OS, the CNI plugin location differs from standard AMIs; ensure you use Bottlerocket-specific configuration. If you upgraded your EKS cluster, the VPC CNI add-on may need manual updating with "Override" conflict resolution. For Windows nodes, the Windows VPC CNI has different initialization; only one ENI is supported per node. If using Karpenter for auto-scaling, ensure nodes are provisioned with the correct subnet configuration before launch templates interfere. For debugging IPAM (IP address management), check /var/log/aws-routed-eni/ipamd.log which logs every IP allocation attempt. Prefix delegation mode (WARM_IP_TARGET and WARM_PREFIX_TARGET) can reduce latency for pod startup; configure via env vars in aws-node DaemonSet if your workload starts many pods rapidly. SELinux and AppArmor on worker nodes can block plugin execution; if hardening is required, coordinate with security team on exceptions. The aws-node pod requires host network access; never add NetworkPolicies blocking kube-system namespace.

Frequently asked questions

What does "EKS CNI plugin error" mean?: AWS EKS uses the Amazon VPC CNI plugin to assign IP addresses from your VPC to Kubernetes pods. This plugin runs as a DaemonSet (aws-node) on every worker node. When the CNI plugin fails to initialize, the kubelet cannot configure networking for containers, leaving nodes in NotReady status and preventing any pods from running.
How do I fix "EKS CNI plugin error"?: The EKS CNI (Container Network Interface) plugin fails to initialize on worker nodes, preventing pods from getting IP addresses and cluster nodes from becoming ready. This typically results from incompatible add-on versions, missing IAM permissions, network connectivity issues, or incorrect network configuration.
What causes "EKS CNI plugin error"?: VPC CNI add-on version is incompatible with your Kubernetes cluster version Missing or incorrect IAM permissions on worker node IAM role (lacking CNI policy) Worker nodes cannot reach the EC2 API endpoint or EKS API server endpoint (port 443)
Is the "EKS CNI plugin error" error serious?: Yes. This is a high-severity error that usually blocks work until it is fixed, but the steps above resolve it.

Official resources & further reading

📚Kubernetes Official Documentation
📖
AWS: Assign IPs to Pods with Amazon VPC CNI(Official Docs)
📖
AWS: Troubleshoot kubelet or CNI plugin issues for EKS(Official Docs)
📖
AWS: Troubleshoot Amazon VPC CNI add-on issues(Official Docs)
📖
GitHub: AWS Amazon VPC CNI for Kubernetes(Official Docs)
📖
AWS: EKS Best Practices Guide - VPC CNI(Official Docs)

How to fix EKS CNI plugin error in Kubernetes

Quick fix

What this error means

Typical symptoms

Common causes

How to fix "EKS CNI plugin error"

Advanced notes

Frequently asked questions

Related errors

Official resources & further reading