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Introduction

Kubernetes has become the cornerstone of cloud-native infrastructure. While its orchestration capabilities are widely recognized, Kubernetes networking remains one of its most complex yet crucial pillars — especially in enterprise-grade deployments.

If you’re running production workloads in Azure Kubernetes Service (AKS), the choice of networking plugin significantly impacts scalability, security posture, observability, and compliance. Enter Azure CNI and Cilium, a pairing that combines Azure-native networking integration with cutting-edge, eBPF-powered security and visibility.

Azure CNI: High-Performance VNet Integration

Azure CNI is not just a network plugin—it’s the bridge between AKS and Azure’s virtual networking fabric.

 How It Works:

• Each pod gets an IP address from the Azure VNet subnet (no NAT).


• This allows direct, routable access between pods and other Azure services (e.g., Azure SQL, Private Endpoints, etc.).


• Network Security Groups (NSGs), Route Tables, and firewalls apply natively.

 Benefits:

• Predictable IP Addressing (no overlay needed)


• Hybrid connectivity ready


• Works seamlessly with Azure Firewall, Azure Application Gateway, and Private Link

However, Azure CNI alone lacks advanced features like application-layer security, identity-based policies, and deep observability. This is where Cilium steps in.

Cilium: eBPF-Powered Networking & Security

Cilium is a revolutionary Kubernetes networking and security project built on eBPF (extended Berkeley Packet Filter)—a Linux kernel technology that allows programmable, high-performance packet processing.

 What Cilium Brings to AKS:

Note: For using FQDN Filtering, L7 Network Policies, Container Network Observability, we need to enable advanced container networking services.

Why Azure CNI + Cilium Together?

• Azure CNI provides robust, native VNet integration


• Cilium enhances security and observability via eBPF

This duo creates a hybrid setup that’s ideal for regulated, performance-sensitive, production workloads.

Architecture Overview

Here’s what this combination looks like in practice:

Pods are directly IP-addressed within Azure VNet (Azure CNI), while Cilium runs as a daemonset/enforcer, applying security policies and exporting observability metrics

Zero Trust Security in AKS Using Cilium

The traditional perimeter firewall model is ineffective in Kubernetes. What you need is workload-level security — and that’s what Cilium delivers.

Security Capabilities:

• Identity-Aware Policies
  Define rules like: “Allow frontend pods to call backend pods only if they use service account X”


• FQDN Policies
  Prevent data exfiltration by whitelisting external domains (e.g., allow only microsoft.com and github.com)


• Protocol-Aware Filtering
  Enforce that service X only allows HTTP GET to /api/* from certain pods — not just any TCP traffic.


• Transparent Encryption
  Secure east-west traffic inside your cluster using WireGuard-based encryption, with zero impact on apps.

Observability with Hubble: No More Blind Spots

Understanding how services communicate in Kubernetes is vital for debugging, auditing, and performance tuning. Cilium ships with Hubble, a distributed observability layer that runs natively on top of eBPF.

 Features of Hubble:

• Service Dependency Graphs


• DNS Query Visibility


• L3–L7 Traffic Flows (who’s talking to whom)


• Dropped Packet Analysis


• Built-in Grafana/Prometheus Dashboards

Conclusion: Modernize Your Cluster Networking the Smart Way

The future of cloud-native networking is kernel-level, programmable, secure by default, and deeply observable.

By adopting Azure CNI with Cilium in AKS, you’re not just provisioning connectivity — you’re enabling:

• Zero-trust network enforcement


• Real-time application flow insights


• High-performance packet processing


• Resilience in a hybrid/multi-cloud environment