Kubernetes Networking with Cilium: eBPF-Based Observability and Security
Why Kubernetes Networking is a Headache?
If you’ve ever tried to set up a Kubernetes cluster—whether on a cloud provider, your own VPS, or a beefy dedicated server—you’ve probably run into networking weirdness. Pods can’t talk to each other. Services are unreachable. Network policies don’t work as expected. And, when you try to debug, it’s like staring into the Matrix. Sound familiar?
That’s because Kubernetes networking is complex. You’re juggling overlay networks, NAT, iptables rules, and a bunch of moving parts. And if you want observability (seeing what’s happening) or security (controlling what’s allowed), things get even trickier. Enter Cilium: a modern, eBPF-powered solution that’s changing the game for Kubernetes networking, security, and observability. Let’s break down why it matters, how it works, and how you can get it running—fast.
What’s the Big Deal with Cilium and eBPF?
- eBPF (extended Berkeley Packet Filter) lets you run sandboxed programs in the Linux kernel, super-fast and safe. Cilium uses eBPF to handle networking, security, and monitoring—right at the kernel level.
- Cilium is a CNI (Container Network Interface) plugin for Kubernetes. It replaces traditional networking plugins (like Flannel, Calico, or Weave) with something much more powerful and flexible.
- Observability and Security: Cilium gives you deep visibility into your network traffic and lets you define security policies that actually work, even in complex microservice environments.
Three Big Questions (and Answers!)
- How does Cilium work under the hood?
- How do I set it up quickly (on cloud, VPS, or dedicated)?
- What are the real-world pros, cons, and gotchas?
1. How Does Cilium Work? (Algorithms, Structure, and the eBPF Magic)
Let’s get a little geeky, but keep it practical. Traditional Kubernetes networking plugins rely on iptables or IPVS for routing and firewalling. These are powerful, but slow and hard to manage at scale. Cilium, on the other hand, uses eBPF to:
- Intercept packets as they enter or leave pods, nodes, or the cluster.
- Apply policies (who can talk to whom, at what layer, with what protocols).
- Collect metrics and traces, so you can see exactly what’s happening.
eBPF programs run in the kernel, so they’re super fast and don’t require context switches to user space. This means:
- Lower latency
- Less CPU overhead
- More accurate observability (no dropped packets in tracing)
Cilium also supports layer 7 (application layer) policies—so you can, for example, allow HTTP GETs but block POSTs between services. Try doing that with iptables!
2. How to Set Up Cilium (Fast!)
Here’s the good news: Cilium is surprisingly easy to install, whether you’re running Kubernetes on a cloud provider, a VPS, or your own dedicated server. Here’s a quick guide:
Prerequisites
- A working Kubernetes cluster (v1.17+ recommended). If you need a VPS or dedicated server, check VPS or dedicated server options.
- kubectl access to your cluster.
- Linux nodes with kernel 4.9+ (5.x preferred for best eBPF support).
Quick Install (the Lazy Way)
The fastest way to get Cilium running is with kubectl and the official manifests:
kubectl create -f https://raw.githubusercontent.com/cilium/cilium/v1.14/install/kubernetes/quick-install.yaml
This will:
- Deploy Cilium as a DaemonSet on all your nodes
- Replace your existing CNI plugin (make sure to remove or disable the old one!)
- Set up basic networking and observability out of the box
Official docs: Cilium Quick Install
Helm Install (for Customization)
If you want to tweak settings (enabling Hubble observability, encryption, etc.), use Helm:
helm repo add cilium https://helm.cilium.io/
helm install cilium cilium/cilium --version 1.14.5 \
--namespace kube-system \
--set hubble.enabled=true \
--set hubble.ui.enabled=true
This enables Hubble, Cilium’s observability platform, with a slick web UI.
Check Everything is Running
kubectl -n kube-system get pods -l k8s-app=cilium
kubectl -n kube-system get pods -l k8s-app=hubble-ui
All pods should be Running. If not, check logs with kubectl logs.
Enable Network Policies
Cilium supports standard Kubernetes NetworkPolicy objects, but you can also use its own more powerful CiliumNetworkPolicy CRDs for L7 rules.
kubectl apply -f https://raw.githubusercontent.com/cilium/cilium/v1.14/examples/kubernetes-network-policy/l3-l4-policy.yaml
3. Real-World Examples, Cases, and Comparisons
| Feature | Cilium (eBPF) | Calico (iptables/BPF) | Flannel (VXLAN) |
|---|---|---|---|
| Performance | High (kernel-level, no user-space hops) | Medium (iptables slow at scale) | Low-Medium (VXLAN overhead) |
| Observability | Excellent (Hubble, L7 tracing) | Basic (flow logs, no L7) | Poor |
| Security Policies | L3-L7, DNS-aware, identity-based | L3-L4, some L7 with BPF | None |
| Cloud Integration | Great (AWS, GCP, Azure, bare metal) | Good | Good |
| Encryption | WireGuard, IPsec, transparent | WireGuard, IPsec | None |
| Beginner Friendly | Yes (quick install, docs) | Yes | Yes |
Positive Case: Microservices with Strict Security
A fintech startup needs to enforce strict network policies between services. With Cilium, they:
- Define L7 policies (e.g., only allow GET requests to payment APIs)
- Visualize traffic flows in real time with Hubble
- Reduce CPU usage compared to iptables-based plugins
Negative Case: Legacy Kernel or Old Kubernetes
A team tries to install Cilium on Ubuntu 16.04 with kernel 4.4. Result: eBPF features are missing, Cilium crashes. Solution: Upgrade to at least kernel 4.9 (ideally 5.x). Always check compatibility!
Beginner Mistakes and Common Myths
- Myth: “eBPF is experimental and unstable.”
Reality: eBPF is used in production at scale (Facebook, Google, Netflix, etc.). Cilium is stable and widely adopted. - Mistake: Not removing the old CNI plugin before installing Cilium.
Tip: Always clean up old CNI configs to avoid conflicts. - Myth: “Cilium is only for cloud.”
Reality: Cilium works great on bare metal, VPS, and even Raspberry Pi clusters! - Mistake: Forgetting to open required ports (e.g., for Hubble UI or Cilium health checks) in your firewall or cloud security groups.
Similar Solutions, Programs, and Utilities
- Calico: Popular, supports eBPF mode, but less feature-rich at L7.
- Flannel: Simple, but only does basic networking (no policies, no observability).
- Weave Net: Easy to set up, but slower and less secure.
- CNI-Genie: Lets you switch between CNIs, but doesn’t solve the core problems.
For observability, Hubble (bundled with Cilium) is a killer feature. It gives you a real-time view of all network flows, DNS lookups, and HTTP/gRPC calls in your cluster.
Interesting Facts and Non-Standard Usage
- Cilium can replace kube-proxy entirely, handling Kubernetes services with eBPF for even better performance. See kube-proxy replacement.
- Transparent Encryption: Cilium can encrypt pod-to-pod traffic with WireGuard or IPsec, with almost no performance penalty.
- DNS-aware policies: You can write policies like “allow traffic to *.github.com” (try that with iptables!).
- Automate Everything: Cilium’s API and CRDs make it easy to automate network policies with scripts or CI/CD pipelines.
- Works with Service Mesh: Cilium integrates with Istio, Linkerd, and others, adding extra security and visibility.
What New Opportunities Open Up?
- Automated Security: Use GitOps to manage network policies as code. Roll out changes safely and audit everything.
- Instant Troubleshooting: Use Hubble to see which pods are talking, what protocols, and where things break—no more guesswork.
- Performance Tuning: Get detailed metrics on network latency, dropped packets, and more, right from the kernel.
- Cloud Agnostic: Move your workloads between cloud, VPS, and bare metal without changing your networking stack.
Conclusion: Should You Use Cilium?
If you’re running Kubernetes—whether on a cloud provider, a VPS from here, or a dedicated server from here—Cilium is a no-brainer for modern networking. It’s fast, secure, and gives you observability that other CNIs just can’t match. Plus, it’s easy to set up and works everywhere Linux runs.
- For production clusters: Get better security, visibility, and performance.
- For hobbyists and tinkerers: Try out eBPF, Hubble, and advanced policies—you’ll learn a ton.
- For automation geeks: Manage everything as code, integrate with CI/CD, and sleep better at night.
Ready to level up your Kubernetes networking? Give Cilium a spin. You’ll wonder how you ever lived without it.
Official project links:
Happy hacking and may your packets always find their way!
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