<p>When I create an EKS cluster I see that worker nodes have two ENIs, eth0 and eth1.</p>

<p>Does EKS require two ENIs for its functionality ? Or two ENIs are added to provide more IPs for the pods (using default AWS CNI) ?</p>

<p>By default EKS uses <code>aws-vpc-cni-k8s</code> to allocate IP addresses for pods.  The default settings for the CNI plugin is <code>WARM_ENI_TARGET=1</code> which will ensure you have an additional ENI available for future assignment.  Your addresses will be assigned to the first ENI until the max IPs per ENI for the instance type is exhausted, then allocations will come from the second ENI.  Once an IP address is assigned to the second ENI a third ENI will be allocated according to the <code>WARM_ENI_TARGET</code> setting.  It will continue to allocate additional ENIs as you use addresses until you reach the maximum number of ENIs for the instance type.</p>
