Configure Azure CNI Powered by Cilium in Azure Kubernetes Service (AKS)

Azure CNI Powered by Cilium combines the robust control plane of Azure CNI with the data plane of Cilium to provide high-performance networking and security.

By making use of eBPF programs loaded into the Linux kernel and a more efficient API object structure, Azure CNI Powered by Cilium provides the following benefits:

• Functionality equivalent to existing Azure CNI and Azure CNI Overlay plugins

• Improved Service routing

• More efficient network policy enforcement

• Better observability of cluster traffic

• Support for larger clusters (more nodes, pods, and services)

IP Address Management (IPAM) with Azure CNI Powered by Cilium

Azure CNI Powered by Cilium can be deployed using two different methods for assigning pod IPs:

• Assign IP addresses from an overlay network (similar to Azure CNI Overlay mode)

Network Policy Enforcement

Cilium enforces network policies to allow or deny traffic between pods. With Cilium, you don't need to install a separate network policy engine such as Azure Network Policy Manager or Calico.

Limitations

Azure CNI powered by Cilium currently has the following limitations:

• Available only for Linux and not for Windows.

• Network policies can't use ipBlock to allow access to node or pod IPs. See frequently asked questions for details and recommended workaround.

• For Cilium versions 1.16 or earlier, multiple Kubernetes services can't use the same host port with different protocols (for example, TCP or UDP) (Cilium issue #14287).

• Network policies aren't applied to pods using host networking (spec.hostNetwork: true) because these pods use the host identity instead of having individual identities.

• Cilium Endpoint Slices are supported in Kubernetes version 1.32 and above. Cilium Endpoint Slices do not support configuration of how Cilium Endpoints are grouped. Priority namespaces through cilium.io/ces-namespace is not supported.

Prerequisites

• Azure CLI version 2.48.1 or later. Run az --version to see the currently installed version. If you need to install or upgrade, see Install Azure CLI.

• If using ARM templates or the REST API, the AKS API version must be 2022-09-02-preview or later.

Create a new AKS Cluster with Azure CNI Powered by Cilium

Option 1: Assign IP addresses from an overlay network

Use the following commands to create a cluster with an overlay network and Cilium. Replace the values for <clusterName>, <resourceGroupName>, and <location>:

az aks create \
    --name <clusterName> \
    --resource-group <resourceGroupName> \
    --location <location> \
    --network-plugin azure \
    --network-plugin-mode overlay \
    --pod-cidr 192.168.0.0/16 \
    --network-dataplane cilium \
    --generate-ssh-keys

Option 2: Assign IP addresses from a virtual network

Run the following commands to create a resource group and virtual network with a subnet for nodes and a subnet for pods.

# Create the resource group
az group create --name <resourceGroupName> --location <location>

# Create a virtual network with a subnet for nodes and a subnet for pods
az network vnet create --resource-group <resourceGroupName> --location <location> --name <vnetName> --address-prefixes <address prefix, example: 10.0.0.0/8> -o none
az network vnet subnet create --resource-group <resourceGroupName> --vnet-name <vnetName> --name nodesubnet --address-prefixes <address prefix, example: 10.240.0.0/16> -o none
az network vnet subnet create --resource-group <resourceGroupName> --vnet-name <vnetName> --name podsubnet --address-prefixes <address prefix, example: 10.241.0.0/16> -o none

Create the cluster using --network-dataplane cilium:

az aks create \
    --name <clusterName> \
    --resource-group <resourceGroupName> \
    --location <location> \
    --max-pods 250 \
    --network-plugin azure \
    --vnet-subnet-id /subscriptions/<subscriptionId>/resourceGroups/<resourceGroupName>/providers/Microsoft.Network/virtualNetworks/<vnetName>/subnets/nodesubnet \
    --pod-subnet-id /subscriptions/<subscriptionId>/resourceGroups/<resourceGroupName>/providers/Microsoft.Network/virtualNetworks/<vnetName>/subnets/podsubnet \
    --network-dataplane cilium \
    --generate-ssh-keys

Frequently asked questions

• Can I customize Cilium configuration?

  No, AKS manages the Cilium configuration and it can't be modified. We recommend that customers who require more control use AKS BYO CNI and install Cilium manually.

• Can I use ClusterwideCiliumNetworkPolicy?

  ClusterwideCiliumNetworkPolicy is not supported.

• Which Cilium features are supported in Azure managed CNI? Which of those require Advanced Container Networking Services?

  Supported Feature	w/o ACNS	w/ ACNS
  Cilium Endpoint Slices	✔️	✔️
  K8s Network Policies	✔️	✔️
  Cilium L3/L4 Network Policies	✔️	✔️
  FQDN Filtering	❌	✔️
  L7 Network Policies (HTTP/gRPC/Kafka)	❌	✔️
  Container Network Observability (Metrics and Flow logs )	❌	✔️

• Why is traffic being blocked when the NetworkPolicy has an ipBlock that allows the IP address?

  A limitation of Azure CNI Powered by Cilium is that a NetworkPolicy's ipBlock can't select pod or node IPs.

  For example, this NetworkPolicy has an ipBlock that allows all egress to 0.0.0.0/0:

  apiVersion: networking.k8s.io/v1
  kind: NetworkPolicy
  metadata:
    name: example-ipblock
  spec:
    podSelector: {}
    policyTypes:
      - Egress
    egress:
      - to:
        - ipBlock:
            cidr: 0.0.0.0/0 # This will still block pod and node IPs.
  

  However, when this NetworkPolicy is applied, Cilium blocks egress to pod and node IPs even though the IPs are within the ipBlock CIDR.

  As a workaround, you can add namespaceSelector and podSelector to select pods. This example selects all pods in all namespaces:

  apiVersion: networking.k8s.io/v1
  kind: NetworkPolicy
  metadata:
    name: example-ipblock
  spec:
    podSelector: {}
    policyTypes:
      - Egress
    egress:
      - to:
        - ipBlock:
            cidr: 0.0.0.0/0
        - namespaceSelector: {}
        - podSelector: {}
  

  Note

  It isn't currently possible to specify a NetworkPolicy with an ipBlock to allow traffic to node IPs.

• Does AKS configure CPU or memory limits on the Cilium daemonset?

  No, AKS doesn't configure CPU or memory limits on the Cilium daemonset because Cilium is a critical system component for pod networking and network policy enforcement.

Next steps

Learn more about networking in AKS in the following articles:

• Upgrade Azure CNI IPAM modes and Dataplane Technology.

• Use a static IP address with the Azure Kubernetes Service (AKS) load balancer

• Use an internal load balancer with Azure Container Service (AKS)

• Create a basic ingress controller with external network connectivity