The Ultimate Guide to Cilium Kubernetes Networking

In a dynamic Kubernetes environment, traditional IP-based firewall rules are fundamentally incompatible with how the platform operates. Pod IPs are ephemeral by design; they change on reschedules, rolling deployments, and autoscaling events. As a result, static allowlists and denylists become brittle, operationally expensive to maintain, and unreliable at scale.

More importantly, IP-centric controls cannot deliver the granularity required for a zero-trust security model. Zero trust assumes no implicit network trust and requires policies that express who is communicating and what they are allowed to do, not merely where traffic originates.

A modern approach shifts security from network addresses to workload identity. Cilium Kubernetes implements this by assigning stable, cryptographic identities to workloads and enforcing policy at the application layer (Layer 7). Instead of coarse network rules, you can define policies that are aware of protocols such as HTTP and gRPC—for example, allowing a specific API endpoint or gRPC method while denying all others. These policies are enforced directly in the kernel using eBPF, providing both strong security guarantees and high performance without the overhead of sidecars.

Key takeaways:

• Replace kube-proxy for better performance: Cilium uses eBPF to handle load balancing and network routing directly in the kernel, which reduces latency and CPU overhead compared to traditional iptables-based solutions.
• Secure services with identity-based policies: Shift from brittle IP address rules to stable, identity-based policies that control communication at the application layer (L7), allowing you to enforce precise rules like permitting specific API calls between services.
• Troubleshoot connectivity with real-time service maps: Use Hubble, Cilium's observability tool, to visualize traffic flows and dependencies, making it easier to diagnose dropped packets and validate that network policies are enforced correctly.

What Is Cilium and How Does It Work in Kubernetes?

Cilium is an open-source platform for networking, security, and observability in cloud-native environments. It's purpose-built for systems like Kubernetes, where workloads are ephemeral and infrastructure state changes continuously.

What differentiates Cilium architecturally is its use of eBPF (Extended Berkeley Packet Filter). Instead of relying on traditional networking primitives such as iptables or user-space proxies, Cilium programs the Linux kernel directly. Networking, security, and observability logic execute in-kernel, close to where packets are processed.

This design avoids the scaling and performance limitations of rule-chain-based systems like iptables, which degrade as rule counts grow. With eBPF, packets are handled via direct lookups and compiled logic paths, enabling predictable performance even in large clusters. For developers and platform teams, this translates into lower latency, higher throughput, and simpler operational models.

Because eBPF programs run in the kernel, Cilium can efficiently inspect and act on traffic without requiring changes to application code or container images. The result is a programmable datapath capable of enforcing fine-grained security policies, performing load balancing, and emitting high-fidelity observability data—all with minimal overhead.

Cilium’s Role in Cloud-Native Networking

Cilium is designed around the realities of microservice-based architectures. In Kubernetes, pods are constantly created, destroyed, rescheduled, and upgraded. Network policy systems must adapt to these changes instantly and deterministically.

Cilium uses eBPF to observe and control traffic at a granular level, dynamically associating policy with workload identity rather than IP address. When a new version of a service is deployed or scaled out, the correct policies are applied automatically, without manual rule updates or service disruption.

This capability is particularly important in large, multi-tenant clusters where workloads are short-lived and security boundaries must be enforced continuously. Cilium ensures that security posture and network behavior remain consistent, even as the underlying topology shifts in real time.

How Cilium Integrates with the Kubernetes CNI

Cilium integrates with Kubernetes by acting as a Container Network Interface (CNI) plugin. When the kubelet schedules a pod onto a node, it invokes the CNI to configure networking for that pod.

A Cilium agent runs on every node as a DaemonSet. This agent watches the Kubernetes API server for changes to pods, services, endpoints, and network policies. Based on this state, it compiles high-level Kubernetes constructs into optimized eBPF programs and loads them into the kernel.

Once loaded, these eBPF programs govern all ingress and egress traffic for pods on that node. Policy enforcement, service load balancing, and traffic visibility occur directly in the datapath, ensuring consistent behavior across the cluster without relying on centralized proxies or per-pod sidecars.

From a developer and platform engineering perspective, this model provides a clean separation between intent (Kubernetes resources) and enforcement (kernel-level datapath), making Cilium a strong foundation for secure, high-performance Kubernetes networking at scale.

How Cilium Uses eBPF for High-Performance Networking

Cilium builds its performance and security model on eBPF, a Linux kernel technology that enables safe, programmable execution inside the kernel. By using eBPF, Cilium implements networking, observability, and security logic directly in the datapath, avoiding slower, legacy mechanisms such as iptables.

This kernel-native approach replaces static, rule-chain-based processing with a highly efficient and programmable datapath. Rather than pushing packets through long sequences of rules, Cilium evaluates traffic using compiled eBPF programs attached to well-defined kernel hook points. Understanding this model is essential to understanding why Cilium scales effectively in modern Kubernetes environments.

For platform teams operating large fleets with tools like Plural, this efficiency is not an optimization detail—it is foundational. Kernel-level policy enforcement ensures consistent performance and security even as services scale, roll, and redeploy continuously.

What Is eBPF and Why Does It Matter?

eBPF (Extended Berkeley Packet Filter) allows developers to run sandboxed programs inside the Linux kernel without modifying kernel source code or loading kernel modules. These programs are verified for safety and then JIT-compiled for efficient execution.

In Kubernetes networking, this capability is transformative. Instead of relying on static, chain-based systems like iptables, Cilium uses eBPF to dynamically inject logic for routing, load balancing, and security enforcement. Policies can change in real time as workloads appear and disappear, aligning the network layer with the ephemeral nature of containers.

This programmability makes the datapath adaptive rather than declarative-only, enabling the network to react immediately to changes in cluster state.

The Performance Advantages of eBPF

The primary performance benefit of eBPF comes from minimizing per-packet overhead. Traditional Kubernetes networking, particularly when implemented via kube-proxy with iptables, requires packets to traverse long rule chains. As clusters grow, these chains become increasingly expensive to evaluate, adding latency and CPU overhead.

Cilium attaches eBPF programs early in the kernel’s networking path, allowing routing and policy decisions to be made with constant-time lookups rather than linear rule traversal. This dramatically reduces latency and improves throughput.

For latency-sensitive workloads—such as real-time analytics, financial systems, or high-QPS APIs—this difference is material. The network remains predictable and scalable as service counts and policy complexity increase.

Kernel-Level Processing for Maximum Efficiency

Cilium’s efficiency is maximized by keeping packet processing entirely in kernel space. In proxy-based models, packets frequently cross the boundary between kernel space and user space, incurring context switches that consume CPU cycles and introduce latency.

With eBPF, Cilium performs load balancing, policy enforcement, and traffic filtering directly in the kernel. Packets are evaluated and forwarded without detouring through user-space components or sidecars.

This kernel-resident processing model is fundamental to Cilium’s low-latency and high-throughput characteristics. It enables platform teams to enforce fine-grained security and networking policies at scale, without compromising performance—an essential requirement for operating modern, cloud-native infrastructure.

Explore Key Cilium Features

Cilium is more than a CNI plugin. It is a full-stack networking, security, and observability platform designed for the realities of Kubernetes. Its core capabilities are built on eBPF and operate directly at the kernel level, enabling high performance, strong security guarantees, and precise control over traffic.

These features address common pain points in cloud-native systems: securing east–west traffic, scaling service networking, and operating across multiple clusters. For platform teams managing Kubernetes fleets with Plural, understanding these primitives is essential to designing secure, scalable infrastructure.

Advanced Network Policies and Microsegmentation

Cilium extends Kubernetes networking with fine-grained, identity-based network policies enforced directly in the kernel. Rather than relying on IP-based rules, policies are evaluated using workload identity, which remains stable across reschedules and deployments.

Cilium supports standard Kubernetes NetworkPolicy resources and augments them with deeper visibility and enforcement using eBPF. This enables true microsegmentation: workloads are isolated by default, and only explicitly allowed communication paths are permitted.

From a security perspective, this minimizes the blast radius of a compromised service and aligns closely with zero-trust principles. Compared to perimeter-based models, policy enforcement is continuous, dynamic, and tightly coupled to workload lifecycle—critical for modern microservices.

Efficient Load Balancing Without kube-proxy

Cilium can fully replace kube-proxy, the default Kubernetes service load balancer. Traditional kube-proxy implementations rely on iptables or IPVS, both of which introduce scaling and performance challenges as service counts grow.

Cilium implements service load balancing directly in the kernel using eBPF. This creates a shorter, more efficient datapath for service traffic, reducing latency and CPU overhead while improving predictability under load.

Removing kube-proxy also simplifies the networking stack. Fewer moving parts means fewer failure modes, easier debugging, and a cleaner mental model for platform engineers operating large clusters.

Multi-Cluster Connectivity and Service Mesh Capabilities

For organizations running multiple Kubernetes clusters, Cilium’s Cluster Mesh enables seamless connectivity between them. Services in different clusters—across regions, clouds, or data centers—can discover and communicate with each other as if they were part of a single cluster.

Cluster Mesh provides transparent service discovery, cross-cluster load balancing, and consistent security policy enforcement. This is foundational for building highly available, geographically distributed systems.

Cilium also integrates naturally with service mesh architectures, providing network-level security and observability without requiring sidecar proxies for basic connectivity. This reduces operational overhead while still supporting advanced traffic visibility across distributed microservices.

Native IP Address Management (IPAM)

IP address exhaustion is a common scaling constraint in large Kubernetes environments, particularly in high pod-density clusters. Cilium includes a native IP Address Management (IPAM) system designed to address this problem directly.

It supports multiple IPAM modes, including cloud-native integrations that allocate pod IPs from secondary network interfaces on virtual machines rather than the node’s primary address range. This dramatically increases the available IP pool without complex network redesigns.

Efficient IP allocation is not just a capacity concern—it directly impacts reliability and scale. Cilium’s IPAM capabilities ensure that clusters can grow predictably without encountering hidden networking limits, which is critical for production environments managed at scale with Plural.

How Cilium Secures Your Kubernetes Environment

Cilium is designed to address the fundamental mismatch between traditional network security models and the realities of Kubernetes. In environments where pods are continuously created, destroyed, and rescheduled, security models based on static IP addresses and firewall rules quickly break down.

Cilium replaces IP-centric controls with a security model built on workload identity, application awareness, and kernel-level enforcement. This enables a zero-trust posture where communication is explicitly allowed based on intent, rather than implicitly trusted based on network location. Policies are enforced efficiently using eBPF, ensuring that strong security does not come at the cost of performance.

At scale, applying and maintaining these controls across many clusters requires consistency and automation. Platforms like Plural complement Cilium by providing GitOps-driven workflows to deploy, configure, and operate Cilium uniformly across large Kubernetes fleets.

Apply Identity-Based Security Policies

In Kubernetes, pod IPs are ephemeral and unsuitable as stable security identifiers. Cilium solves this by assigning cryptographic security identities to workloads based on Kubernetes labels. All pods sharing the same label set—such as app=api—share a common identity, regardless of where or when they are scheduled.

Security policies are written in terms of these identities rather than IP addresses. For example, you can allow traffic from a frontend identity to an api identity on a specific port, without referencing any network addresses. As pods scale, move, or are replaced, the policy remains valid without manual updates.

This identity-based model aligns security policy directly with application architecture, making rules easier to reason about and far more resilient in dynamic environments.

Enforce Layer 7 Application-Level Controls

Most Kubernetes network policies operate at Layer 3 and Layer 4, controlling traffic based on IPs, ports, and protocols. Cilium extends enforcement to Layer 7, enabling policies that understand application protocols such as HTTP, gRPC, and Kafka.

This allows you to define intent-driven rules, such as permitting a service to issue GET requests to a specific API endpoint while denying POST or DELETE operations. Instead of broad port-level access, policies can be scoped to individual methods and paths.

Layer 7 enforcement is critical for applying the principle of least privilege and limiting lateral movement. By understanding application context, Cilium enforces security policies that are significantly more precise than traditional network filtering.

Enable Transparent Pod-to-Pod Encryption

Protecting data in transit is a baseline requirement for many production environments. Cilium provides transparent pod-to-pod encryption using efficient kernel-level technologies such as IPsec and WireGuard.

Encryption is handled entirely by the networking layer, requiring no changes to application code or container images. Once enabled, all east–west traffic between pods is automatically encrypted, protecting sensitive data even if the underlying network is compromised.

This capability is particularly important for regulated workloads and helps meet compliance requirements such as PCI DSS and HIPAA, while maintaining high throughput and low latency.

Use eBPF for Runtime Security Enforcement

Cilium’s security model is enforced using eBPF programs that run directly inside the Linux kernel. These programs inspect packets, apply policy decisions, and allow or drop traffic before it reaches application processes.

By executing in kernel space, Cilium avoids the overhead of user-space proxies and context switches. Enforcement is fast, consistent, and difficult to bypass, since all traffic traverses the same kernel datapath.

This runtime enforcement model enables deep visibility and strong security guarantees without introducing performance bottlenecks. It is a key reason Cilium can provide advanced security, observability, and networking capabilities at scale—making it well-suited for large Kubernetes environments managed with platforms like Plural.

How to Install and Configure Cilium

Installing Cilium is the foundational step to enabling eBPF-powered networking and security in Kubernetes. The workflow is straightforward but opinionated: validate prerequisites, choose an installation mechanism aligned with your operational model, and verify datapath correctness post-install.

Cilium supports multiple installation paths, with the official CLI and Helm charts being the most common. The right choice depends on whether you are optimizing for rapid evaluation or for production-grade, GitOps-managed deployments. Regardless of method, correctness hinges on kernel compatibility and post-install validation to ensure policies, load balancing, and encryption features function as expected.

Prerequisites and System Requirements

Before deploying Cilium, you need a functional Kubernetes cluster and a configured kubectl context. For meaningful validation, the cluster should include at least two worker nodes so inter-node pod traffic can be exercised.

The most important prerequisite is the Linux kernel version on your nodes. Because Cilium relies on eBPF for datapath and policy enforcement, kernel support is non-negotiable. A Linux kernel version of 4.9 or newer is generally required, with newer kernels providing better performance and feature coverage. Always verify compatibility against the Cilium version you plan to deploy, as specific capabilities may require more recent kernels.

Meeting these baseline requirements upfront avoids the most common installation failures and runtime anomalies.

Choose Your Installation Method

Cilium can be installed using either the Cilium CLI or Helm, each optimized for different use cases.

The Cilium CLI is well-suited for development, testing, and quick evaluations. Running cilium install auto-detects cluster characteristics and applies a set of sane defaults, minimizing initial setup friction.

For production environments, Helm is the preferred approach. The official Cilium Helm chart exposes the full configuration surface, allowing you to enable or tune features such as kube-proxy replacement, Hubble observability, IPAM modes, and encryption. Helm-based installs integrate cleanly with GitOps tooling such as Argo CD and Flux, which is how platforms like Plural manage consistent Cilium deployments across large Kubernetes fleets.

From an operational standpoint, Helm provides the repeatability and auditability required for long-lived clusters.

Basic Configuration and Validation

After installation, validation is mandatory. The first checkpoint is the cilium status command, which reports the health of the Cilium agents, operator components, and core datapath features. This confirms that the control plane is up and the agents are successfully programming eBPF into the kernel.

For end-to-end verification, run the cilium connectivity test. This deploys temporary workloads and exercises multiple traffic patterns, including pod-to-pod, pod-to-service, and policy-restricted flows. A clean pass indicates that networking, service load balancing, and policy enforcement are functioning correctly.

If issues arise, Cilium provides comprehensive diagnostics and troubleshooting documentation. Resolving problems at this stage is critical, as a correctly validated CNI is the prerequisite for safely enabling advanced features such as identity-based policies, Layer 7 enforcement, and transparent encryption—capabilities that become significantly easier to operate at scale when managed through platforms like Plural.

Implement Cilium Network Policies: Best Practices

Implementing network policies with Cilium is not just a matter of authoring YAML manifests. It is about defining a security posture that is explicit, resilient, and operationally sustainable as your Kubernetes environment evolves.

Well-designed policies protect services without slowing down delivery. That requires a clear strategy, deliberate use of Cilium’s enforcement capabilities, and continuous visibility into traffic behavior. Starting with sound best practices helps avoid brittle configurations, policy sprawl, and accidental outages as clusters and teams scale. A layered approach, phased enforcement, and disciplined operations are the foundation of a secure zero-trust network.

Create and Manage Layer 3/4 and Layer 7 Policies

Cilium’s core advantage is its ability to enforce policies at both Layer 3/4 and Layer 7. Layer 3/4 policies control traffic based on source and destination identity, ports, and protocols. Layer 7 policies extend this model by inspecting application-level semantics such as HTTP methods, URL paths, gRPC services, or Kafka topics.

A common and effective pattern is to establish a coarse-grained baseline using Layer 3/4 rules, then selectively introduce Layer 7 controls for high-value or high-risk services. For example, you might allow a frontend service to reach a backend API at the network level, then restrict that access to GET /products while explicitly denying mutating operations.

This defense-in-depth model limits blast radius while keeping policy sets understandable. Applying Layer 7 policies everywhere from day one often leads to unnecessary complexity; introducing them incrementally ensures security gains without sacrificing operability.

Understand Policy Enforcement Modes

Cilium provides flexible enforcement modes that allow teams to introduce security controls gradually. Policies can initially run in a non-enforcing or audit-only mode, where decisions are logged but traffic is not blocked. This is critical for understanding real communication patterns and validating intent before enforcing restrictions.

Once confidence is established, policies can be moved into full enforcement. A widely accepted best practice is to work toward a default-deny posture, where all traffic is denied unless explicitly allowed. While this model provides the strongest security guarantees, it requires accurate knowledge of service dependencies.

Using Cilium’s enforcement modes to transition progressively toward default deny reduces risk and avoids production disruptions while still aligning with zero-trust principles.

Follow Safe Upgrade and Monitoring Strategies

Operating Cilium safely at scale requires disciplined upgrade and monitoring practices. Always review release notes for behavioral changes, datapath updates, or new kernel requirements before upgrading. Canary upgrades—where a subset of nodes is updated first—are a proven strategy for catching issues early.

During upgrades, continuous monitoring of both control plane and datapath health is essential. Key signals include policy propagation latency, error rates, packet drops, and API server interactions. Any deviation from baseline should be investigated before proceeding with a full rollout.

Platforms like Plural simplify this operational burden by aggregating observability signals across clusters into a single, consistent view. This consolidated perspective makes it easier to detect anomalies during policy changes or upgrades and ensures that network security improvements do not come at the expense of reliability.

By combining layered policies, phased enforcement, and rigorous operational discipline, teams can use Cilium to build a secure, scalable, and maintainable networking foundation for Kubernetes.

Gain Network Observability with Cilium and Hubble

High-performance networking and security are only effective if you can observe and understand their behavior in production. Cilium addresses this requirement through Hubble, its native observability layer.

Because Cilium operates directly in the Linux kernel using eBPF, Hubble can capture detailed network telemetry with minimal overhead. This provides continuous visibility into real traffic flows, policy decisions, and service interactions—without requiring application changes or sidecar proxies. For platform teams, this level of insight is essential for troubleshooting, security auditing, and performance optimization.

Hubble exposes this data through a UI, CLI, and API, enabling flexible access patterns. While Cilium and Hubble generate the raw telemetry, operating this at fleet scale introduces complexity. Platforms like Plural aggregate and normalize this data across clusters, presenting a single-pane-of-glass view that correlates network events with application and infrastructure signals.

Use Hubble for Deep Network Visibility

Hubble is purpose-built for Cilium and integrates directly with its eBPF datapath. This allows it to observe every network flow—successful or denied—without modifying workloads or introducing additional runtime components.

Hubble provides detailed, application-aware context rather than raw packet metadata. You can inspect flows by Kubernetes labels, namespaces, and identities, and see exactly how network policies are evaluated. When a connection is dropped, Hubble shows the verdict and the specific policy responsible.

This level of precision significantly reduces mean time to resolution when debugging connectivity issues in complex microservices environments. The Hubble UI makes these insights accessible through intuitive visualizations, while the CLI and API support automation and scripting.

Map Service Interactions in Real Time

Hubble can automatically generate live service maps based on observed traffic. These maps visualize how services communicate in real time, revealing actual dependencies rather than intended architecture.

For dynamic Kubernetes environments, this capability is critical. It allows teams to verify microsegmentation rules, detect unexpected communication paths, and understand the impact of new deployments immediately. When a new service is introduced, its upstream and downstream dependencies appear automatically, providing instant feedback on whether traffic aligns with expectations.

This real-time visibility helps teams iterate faster while maintaining a strong security posture, as deviations from intended communication patterns are easy to spot and investigate.

Monitor the Control Plane and Datapath

Effective observability requires monitoring both the control plane and the datapath. The control plane distributes policies and configuration, while the datapath—implemented with eBPF—enforces those policies on live traffic. Issues in either layer can lead to security gaps or connectivity failures.

Cilium exposes a comprehensive set of metrics via Prometheus, including packet drops, policy enforcement counts, service load-balancing behavior, API server interactions, and IPAM usage. Tracking these signals allows teams to detect misconfigurations, performance regressions, and capacity constraints early.

Aggregating these metrics into a centralized platform such as Plural’s observability console enables consistent dashboards and alerting across clusters. This unified view is essential for operating Cilium and Hubble reliably at scale, ensuring that network visibility keeps pace with the growth and complexity of your Kubernetes environment.

Cilium vs. Other CNI Plugins

Choosing the right Container Network Interface (CNI) plugin has a direct impact on Kubernetes performance, security posture, and operational complexity. While most CNIs solve basic pod-to-pod connectivity, Cilium takes a fundamentally different approach by building its datapath on eBPF rather than legacy kernel mechanisms.

Traditional CNIs such as Calico or Flannel typically rely on iptables or IPVS for routing, policy enforcement, and service handling. These approaches work, but they were not designed for the scale, churn, and policy density common in modern Kubernetes clusters. Cilium’s eBPF-based model addresses these constraints directly.

Comparing Cilium to Traditional CNIs

Most traditional CNI plugins establish networking using virtual interfaces, routing tables, and iptables rules. As pods and services scale, iptables rule chains grow linearly, increasing CPU overhead and packet-processing latency. Debugging also becomes harder, as behavior emerges from long, ordered rule lists that are difficult to reason about.

Cilium replaces this model with eBPF programs attached directly to kernel hook points. Network decisions are made using efficient map lookups rather than sequential rule evaluation. This produces a shorter, more predictable datapath and scales cleanly as clusters grow.

Because Cilium operates closer to the kernel, it can enforce policies and route traffic without depending on large rule tables or external proxies. The result is higher throughput, lower latency, and more deterministic behavior in high-churn environments.

Key Differentiators: Performance and Features

Cilium’s core differentiator is its eBPF-based architecture, which enables capabilities that are difficult or inefficient to implement with traditional CNIs.

First, Cilium supports identity-based and application-aware (Layer 7) policies. Instead of limiting access by IP and port, policies can be expressed in terms of service identity and API semantics—for example, allowing GET requests to a specific endpoint while denying mutating operations. This level of control is not practical with iptables-based systems.

Second, Cilium can fully replace kube-proxy. Service load balancing is implemented directly in the kernel using eBPF hash tables, eliminating the iptables or IPVS chains kube-proxy depends on. This simplifies the networking stack and significantly improves service traffic performance and predictability.

Finally, Cilium’s tight integration with observability tooling (via Hubble) provides real-time insight into policy decisions and traffic flows, something traditional CNIs struggle to deliver without sidecars or external probes.

When to Choose Cilium

Cilium is well suited for environments that prioritize performance, security depth, and visibility. Large clusters, high pod churn, complex microservice topologies, and zero-trust networking models all benefit from Cilium’s identity-based policies and kernel-level enforcement.

If your workloads require granular, application-aware controls, multi-cluster connectivity, or deep network observability, Cilium provides a strong long-term foundation. It also scales well from local testing to production, making it viable across the entire lifecycle of a platform.

For smaller clusters with simple requirements—where only basic Layer 3/4 policies are needed—a simpler CNI may be sufficient. However, as observability needs grow or architectures become more distributed, teams often outgrow these solutions.

Operating Cilium at scale does introduce configuration and lifecycle complexity. Platforms like Plural address this by standardizing deployments, automating upgrades, and enforcing policy consistency across clusters, making it easier to adopt Cilium’s advanced capabilities without increasing operational burden.

Get Started with Cilium in Your Cluster

Getting Cilium up and running in your Kubernetes cluster is a straightforward process designed to quickly enhance networking, security, and observability. Here are the essential steps to get started.

First, you'll need to install the Cilium command-line tool. Once the CLI is ready, a single cilium install command handles the deployment. This command bootstraps Cilium by creating the necessary service accounts, security certificates, and deploying the Cilium agent as a DaemonSet. This ensures the agent runs on every node, where it enforces network policies and gathers observability data. The official Kubernetes documentation provides a detailed guide on how to use Cilium for NetworkPolicy.

With Cilium installed, you can immediately begin to define rules that govern application communication. These NetworkPolicies are a standard Kubernetes resource, but Cilium uses eBPF to enforce them with greater performance and flexibility. You can create policies to control traffic between pods and to external services, which is a fundamental step in securing your environment.

You also gain deep network observability right out of the box. Cilium's built-in tools provide detailed insights into traffic flows and application behavior, which is invaluable for troubleshooting. While Cilium provides its own observability through tools like Hubble, this visibility can be integrated into a centralized platform. For instance, Plural's embedded Kubernetes dashboard offers a single pane of glass to monitor cluster health and resources, complementing the granular network data from Cilium.

As you move toward production, be aware of common challenges. In large or dense clusters, IP address exhaustion can become a problem. Cilium helps you mitigate this issue with its native IP Address Management (IPAM) mode, which optimizes IP allocation to ensure your cluster can scale efficiently. Following these steps will help you build a solid foundation for using Cilium to secure and manage your Kubernetes networking.

Related Articles

• Cilium Kubernetes: Next-Gen Networking & Security

Frequently Asked Questions

Is it difficult to switch to Cilium from another CNI like Calico or Flannel? Migrating your CNI requires careful planning but is a well-understood process. It typically involves a rolling update of your cluster nodes to avoid downtime. The general approach is to install the Cilium agent on each node, update the kubelet configuration to use Cilium as the CNI plugin, and then restart the kubelet. This process is repeated node by node. While this is manageable for a single cluster, ensuring a consistent and error-free migration across an entire fleet demands automation. Using a GitOps-based platform like Plural allows you to manage this configuration as code, ensuring every cluster is updated uniformly and reliably.

Do I need to change my application code to use Cilium's Layer 7 network policies? No, you do not need to modify your application code or container images. This is one of the primary benefits of Cilium's eBPF-based approach. Cilium inspects network traffic transparently at the kernel level, allowing it to understand application protocols like HTTP, gRPC, and Kafka without any sidecar proxies or application-side agents. This means you can enforce granular rules, such as allowing GET requests while blocking POST requests to a specific API endpoint, without adding any operational overhead to your development teams.

What are the tangible benefits of replacing kube-proxy with Cilium? Replacing kube-proxy removes a significant performance bottleneck and simplifies your cluster's networking stack. Kube-proxy typically uses iptables or IPVS for service load balancing, which can become slow and inefficient in large clusters with many services. Cilium handles this function directly in the kernel using highly efficient eBPF hash tables. This results in lower latency for service-to-service communication, higher throughput, and a more reliable data plane. It also reduces the overall complexity of your cluster, making it easier to troubleshoot and maintain.

How does Cilium handle security for services that run outside my Kubernetes cluster? Cilium can extend its identity-based security model to external workloads, such as a database running on a virtual machine. You can define policies that control traffic between pods inside the cluster and specific IP addresses or DNS names outside of it. For more advanced use cases, Cilium can integrate with your physical network using BGP to advertise pod IP routes. This enables direct, routable communication between pods and external services without requiring network address translation (NAT), which simplifies the network architecture and improves performance.

If I adopt a 'default-deny' policy, how can I avoid breaking my applications? The safest way to implement a zero-trust, default-deny security posture is to do it gradually. Cilium is designed for this with its policy enforcement modes. You can begin by applying your network policies in "audit mode," where Cilium logs any traffic that would have been dropped but doesn't actually block it. Using an observability tool like Hubble, you can then analyze these logs to understand your application's real-world communication patterns and refine your policies. Once you are confident that your rules correctly allow all legitimate traffic, you can switch the policies to full enforcement mode, preventing accidental service disruptions.