Securely Deploying a Network-Isolated Azure Kubernetes Service (AKS) Cluster

 

Introduction

In today cloud landscape, securing the containerized applications the Azure Kubernetes service has introduced the network isolated AKS cluster management. This approach will lead to mitigate from critical aspects of AKS deployments with ensuring the network isolation by preventing from potential threats from public internet.

This blog will provide a technical overview of designing deploying and managing the network isolated AKS cluster. Whether you're working on compliance-critical applications or sensitive workloads, this guide ensures your AKS environment remains secure and robust.

Why Network Isolation is so important AKS?

1. Prevents Unauthorized Access: Restricts access to the cluster's API server and workloads.
2. Reduces Attack Surface: Eliminates exposure to the internet for AKS components and dependencies.
3. Facilitates Regulatory Compliance: Meets the security standards such as GDPR, HIPAA, and PCI DSS.

By deploying a network-isolated AKS, organizations can ensure the workloads communicate securely within defined private boundaries.

Major Components that we should consider on a Network-Isolated AKS Deployment

1. Virtual Network (VNet)

A Virtual Network acts as the foundational layer.

• Subnets: Define subnets for the AKS system nodes, pods, and services.
• Azure CNI: Use Azure Container Networking Interface (CNI) to assign IPs to pods directly from the VNet.

2. Private Cluster

Enable the AKS API server to be accessible only through a private endpoint within the VNet. This eliminates public API exposure.

3. Private Endpoints for Dependencies

Set up private endpoints for services like Azure Container Registry (ACR) and Azure Monitor to keep communication private.

4. DNS Integration

Integrate private DNS zones to resolve private endpoint IPs.

5. Network Security Groups (NSGs)

Control ingress and egress traffic at the subnet level by configuring NSG rules.

6. Azure Firewall or NVAs

Introduce Azure Firewall or third-party Network Virtual Appliances (NVAs) for advanced traffic filtering and inspection.

7. Bastion or Jump box Access

Use Azure Bastion or a hardened VM for secure access to the cluster.

Step-by-Step Guide to Deploy a Network-Isolated AKS Cluster

Step 1: Prerequisites

1. Azure subscription with appropriate permissions.
2. Azure CLI, kubectl, and Terraform installed on your local machine.
3. Network planning with defined CIDR ranges for subnets.

Step 2: Create a Virtual Network and Subnets

bash

az network vnet create \

  --name AKSVNet \

  --resource-group TestResourceGroup \

  --address-prefix 10.0.0.0/16 \

  --subnet-name AKSSubnet \

  --subnet-prefix 10.1.0.0/24

Repeat for additional subnets as required (e.g., for private endpoints).

Step 3: Deploy a Private AKS Cluster

Use Azure CLI to deploy a private AKS cluster:

bash

az aks create \

  --resource-group TestResourceGroup \

  --name AKSCluster \

  --enable-private-cluster \

  --vnet-subnet-id <subnet-id> \

  --network-plugin azure \

  --node-vm-size Standard_D4s_v3 \

  --enable-managed-identity \

  --enable-addons monitoring \

  --generate-ssh-keys

Step 4: Configure Private Endpoints

For Azure Container Registry (ACR):

1. Enable a private endpoint:

bash

az network private endpoint create \

  --name acrPrivateEndpoint \

  --resource-group TestResourceGroup \

  --vnet-name AKSVNet \

  --subnet PrivateEndpointSubnet \

  --private-connection-resource-id <acr-id> \

  --group-id registry

2. Link the private DNS zone:

bash

az network private-dns zone create \

  --resource-group TestResourceGroup \

  --name "privatelink.azurecr.io"

Associate the zone with the VNet.

Step 5: Configure NSGs for Traffic Control

Define rules to allow traffic only from trusted IP ranges:

bash

az network nsg rule create \

  --nsg-name AKSNSG \

  --resource-group TestResourceGroup \

  --name AllowSSH \

  --priority 100 \

  --direction Inbound \

  --access Allow \

  --protocol Tcp \

  --source-address-prefixes <trusted-ip-range> \

  --destination-port-ranges 22

Step 6: Integrate Azure Firewall

Deploy Azure Firewall for advanced traffic filtering:

bash

az network firewall create \

  --name TestAzureFirewall \

  --resource-group TestResourceGroup \

  --vnet-name AKSVNet

Step 7: Validate the Deployment

1. Test connectivity to the AKS API server from within the VNet.
2. Verify workloads communicate with private endpoints for dependencies.
3. Use Azure Monitor and Network Watcher to inspect traffic.

Best Practices

1. Use Managed Identities: Avoid storing credentials in code.
2. Enable Defender for Kubernetes: Add advanced threat detection.
3. Monitor with Azure Monitor: Gain visibility into the cluster and network activity.
4. Regularly Update Rules: Periodically review NSG and firewall rules.
5. Enable Pod Security Policies: Restrict pod behavior to minimize risks.

Use Cases for Network-Isolated AKS Clusters

• Regulatory Compliance: For industries like finance, healthcare, and government.
• Multi-Tenancy: Ensuring tenants workloads remain isolated.
• Hybrid Deployments: Securely connect on-premises systems with Azure.

Conclusion

By deploying a network-isolated AKS cluster, you not only protect your workloads but also enhance compliance and maintain robust security standards. Whether you're a seasoned cloud architect or a developer prioritizing security, these steps and best practices will guide you toward a successful deployment.