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AKS clusters using Azure CNI should use large subnets#

Performance Efficiency · Azure Kubernetes Service · Azure.AKS.CNISubnetSize

AKS clusters using Azure CNI should use large subnets to reduce IP exhaustion issues.

Description#

In addition to kubenet, AKS clusters support Azure Container Networking Interface (CNI). This enables every pod to be accessed directly from the subnet via an IP address. Each node supports a maximum number of pods, which are reserved as IP addresses. This approach requires more capacity planning ahead of time, and can result in IP address exhaustion or the need to rebuild AKS clusters into larger subnets as application workloads begin to grow.

Recommendation#

Consider allocating a large subnet(/23 or bigger) to your AKS cluster.

Notes#

This rule applies when analyzing resources deployed to Azure using Export in-flight resource data.

This rule fails when the CNI subnet size is smaller than /23.

Configure AZURE_AKS_CNI_MINIMUM_CLUSTER_SUBNET_SIZE to set the minimum AKS CNI cluster subnet size.

# YAML: The default AZURE_AKS_CNI_MINIMUM_CLUSTER_SUBNET_SIZE configuration option
configuration:
  AZURE_AKS_CNI_MINIMUM_CLUSTER_SUBNET_SIZE: 23

Last update: 2021-10-19