Kubernetes Networking in 2025: From CNI Chaos to eBPF Precision

It is 3:00 AM on a Tuesday. Your monitoring dashboard is bleeding red. The frontend pods are up, the database is healthy, but traffic is disappearing into the void between nodes. Welcome to Kubernetes networking.

In the last five years, we have seen the ecosystem shift from the simple days of Flannel and heavy usage of iptables to the high-performance era of eBPF. If you are still relying on legacy packet forwarding rules for a high-traffic cluster targeting the Nordic market, you are essentially running a race car on square wheels.

I have spent the last decade debugging distributed systems, from bare metal racks in basement data centers to massive cloud clusters. The lesson remains the same: Latency is the only metric that honest engineering cannot fake.

The Death of iptables and the Rise of eBPF

Back in 2020, kube-proxy using iptables was the standard. It worked, but at scale, it was a disaster. Every service update forced a recalculation of thousands of rules. By March 2025, if you aren't using eBPF (Extended Berkeley Packet Filter), you are doing it wrong.

We use Cilium as the de facto CNI (Container Network Interface) for high-performance workloads. Unlike iptables, which operates in a sequential list, eBPF allows us to run sandboxed programs in the kernel, processing packets at near-wire speed without the context-switching overhead.

Pro Tip: When deploying K8s on virtualized infrastructure, ensure your underlying host supports virtio-net with multi-queue enabled. At CoolVDS, our KVM instances expose the CPU topology correctly, allowing the guest OS to parallelize packet processing. Without this, your fancy CNI is bottlenecked by a single vCPU interrupt.

Configuring Cilium for Zero-Trust

Security in 2025 isn't about firewalls at the edge; it's about identity-aware micro-segmentation. Here is a production-grade CiliumNetworkPolicy that restricts traffic based on Layer 7 metadata, not just IP addresses. This is critical for compliance with Norwegian regulations where data minimization is key.

apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
  name: "secure-payment-gateway"
  namespace: "finance"
spec:
  endpointSelector:
    matchLabels:
      app: payment-processor
  ingress:
  - fromEndpoints:
    - matchLabels:
        app: checkout-frontend
    toPorts:
    - ports:
      - port: "8080"
        protocol: TCP
      rules:
        http:
        - method: "POST"
          path: "/v1/charge"
  egress:
  - toFQDNs:
    - matchName: "api.stripe.com"
  - toEndpoints:
    - matchLabels:
        app: postgres-db

This configuration ensures that your payment processor only accepts POST requests from the frontend and can only talk to Stripe and its specific database. If an attacker compromises the frontend, they cannot pivot to scan your internal network.

The Gateway API Standard

The old Ingress resource was ambiguous. By 2025, the Gateway API has matured into the standard for exposing services. It separates the infrastructure (the Gateway) from the routing logic (HTTPRoute), allowing Ops and Devs to work without stepping on each other's toes.

Here is how we split traffic between a canary deployment and a stable release, a common requirement for teams pushing updates during business hours in Oslo:

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: "store-traffic-split"
  namespace: "production"
spec:
  parentRefs:
  - name: "external-gateway"
  hostnames:
  - "shop.coolvds-client.no"
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /cart
    backendRefs:
    - name: "cart-service-v1"
      port: 80
      weight: 90
    - name: "cart-service-v2"
      port: 80
      weight: 10

Infrastructure Matters: The CoolVDS Advantage

You can have the best CNI and the cleanest Gateway config, but if your underlying VPS suffers from "noisy neighbor" syndrome or I/O wait, your networking will stall. Kubernetes is chatty. Etcd requires low latency for consensus. If your disk write latency spikes because another tenant on the host is mining crypto, your cluster leader election fails.

This is where architecture counts. We don't overcommit RAM. We use NVMe storage exclusively. When you run a ping from a CoolVDS instance in Oslo to NIX (Norwegian Internet Exchange), you are seeing the raw physics of fiber optics, not the jitter of a congested hypervisor queue.

Debugging Network Latency

When things break, tcpdump is often too low-level and kubectl logs is too high-level. In 2025, we use Hubble (part of the Cilium stack) to visualize flows.

To identify dropped packets due to policy violations:

hubble observe --verdict DROPPED --namespace finance -f

To measure the latency of DNS requests (often the silent killer of performance):

hubble observe --to-fqdn "*.google.com" -o json | jq '.flow.l7.dns'

If you see DNS resolution taking over 50ms, check your NodeLocal DNSCache settings. But if the resolution is fast and the TCP handshake is slow, check your node-to-node latency. On CoolVDS, inter-node latency within our Oslo datacenter is typically sub-millisecond.

Local Compliance: The Norwegian Context

Deploying Kubernetes in Norway involves more than just YAML. You have Datatilsynet and GDPR to contend with. The Schrems II rulings made reliance on US-owned cloud providers legally risky for sensitive data.

By hosting your Kubernetes nodes on CoolVDS, you ensure data residency remains strictly within Norway. Our infrastructure is owned and operated locally. We don't ship your packet metadata across the Atlantic for "analysis."

Final Thoughts

Kubernetes networking is unforgiving. It demands precision at the config level and raw power at the infrastructure level. Don't let a cheap VPS provider be the bottleneck that crashes your production environment during Black Friday.

Need a cluster that respects the laws of physics? Spin up a CoolVDS high-performance instance today and see what real low latency feels like.