Kubernetes Networking in 2024: De-mystifying the Packet Path

Most developers treat Kubernetes networking as magic. You define a Service, throw in an Ingress, and somehow traffic lands on the right Pod. That works fine until you hit 5,000 requests per second (RPS) or experience a 200ms latency spike because your traffic hairpin-turned through a data center in Frankfurt instead of staying local in Oslo.

I've spent the last decade debugging distributed systems, and if there is one truth in 2024, it is this: abstraction is expensive. Kubernetes adds layers. Your job is to peel them back.

This isn't a "Hello World" tutorial. We are going to look at how packets actually move, why iptables is your enemy at scale, and how to configure a network stack that keeps the Datatilsynet happy and your latency low.

The CNI Decision: Why eBPF is Non-Negotiable in 2024

In the early days (circa 2017), we used Flannel and we liked it because it was simple. VXLAN encapsulation was acceptable. But today, if you are running a production workload on a VPS in Norway, you should be looking at eBPF-based CNIs. Specifically, Cilium.

Why? Because traditional iptables-based routing is O(N). As your Services grow, the rule list gets longer, and packet processing slows down. eBPF allows us to run sandboxed programs in the kernel, bypassing much of the stack.

Here is a battle-tested Cilium configuration for a high-performance cluster. Note the kubeProxyReplacement enabling strict datapath optimization:

# cilium-values.yaml
kubeProxyReplacement: true
k8sServiceHost: API_SERVER_IP
k8sServicePort: 6443
l2announcements:
  enabled: true
bgpControlPlane:
  enabled: true
ipam:
  mode: "kubernetes"
loadBalancer:
  mode: "dsr" # Direct Server Return - crucial for throughput

Pro Tip: Using DSR (Direct Server Return) prevents the return traffic from hopping back through the load balancer node. It goes straight from the worker node to the client. On CoolVDS KVM instances, we've seen this reduce latency by 15-20% for bandwidth-heavy workloads.

Service Discovery: Moving Beyond iptables

If you aren't ready for full eBPF, or you are inheriting a legacy cluster, you must at least ditch the default iptables mode in kube-proxy. Switch to IPVS (IP Virtual Server). It uses hash tables instead of linear lists.

I once debugged a cluster in Trondheim where service resolution took 50ms simply because iptables had 20,000 rules. We switched to IPVS, and it dropped to 2ms.

Configuring kube-proxy for IPVS

You can edit the config map directly in the kube-system namespace:

kubectl edit configmap kube-proxy -n kube-system

Look for the mode setting and ensure strict ARP configuration:

apiVersion: kubeproxy.config.k8s.io/v1alpha1
kind: KubeProxyConfiguration
mode: "ipvs"
ipvs:
  strictARP: true
  sched: "rr" # Round Robin is usually sufficient
  tcpTimeout: 0s
  tcpFinTimeout: 0s
  udpTimeout: 0s

The Gateway API Shift

By late 2024, the Ingress resource is effectively "maintenance mode." The Gateway API is the standard for defining routing. It separates the infrastructure (the Gateway) from the routing logic (HTTPRoute).

This separation is critical for multi-tenant teams. The SysAdmin defines the listener and TLS termination, while the Dev team defines the path rewriting.

Here is a standard HTTPRoute example that splits traffic (canary deployment) without needing a service mesh:

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: checkout-route
spec:
  parentRefs:
  - name: external-gateway
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /checkout
    backendRefs:
    - name: checkout-v1
      port: 8080
      weight: 90
    - name: checkout-v2
      port: 8080
      weight: 10

The Hardware Reality: Why Your VPS Provider Matters

You can tune sysctls all day, but you cannot software-engineer your way out of bad hardware or poor peering. Kubernetes is chatty. etcd requires low latency to maintain consensus. If your disk I/O waits, the API server hangs, and your networking updates stall.

This is where the choice of hosting becomes architectural, not just financial. In Norway, data sovereignty (Schrems II) and latency to NIX (Norwegian Internet Exchange) are paramount.

The CoolVDS Advantage:

• NVMe Latency: We don't use spinning rust or network-attached storage for root volumes. This keeps etcd write latency consistently under 2ms.
• Virtio-net Drivers: Our KVM implementation exposes virtio-net, allowing the guest OS (your K8s node) to offload packet processing to the host efficiently.
• Peering: Direct routes to major Norwegian ISPs mean your packets don't take a detour through Sweden to reach a user in Oslo.

Troubleshooting: When the Packet Drops

When networking fails, don't guess. Use nsenter to inspect the container's network namespace from the host. This is safer than installing debug tools inside your production images.

# 1. Find the PID of the container
PID=$(crictl inspect --output go-template --template '{{.info.pid}}' <container_id>)

# 2. Enter the network namespace
nsenter -t $PID -n ip addr show

Once inside, you can run tcpdump to see exactly what the pod sees, bypassing any host-level filtering that might confuse you.

Final Thoughts: Latency is the New Downtime

In 2024, users expect instant interactions. A 500ms delay in a checkout flow is a lost sale. By leveraging eBPF, adopting the Gateway API, and ensuring your underlying infrastructure—like CoolVDS NVMe instances—can handle the IOPS, you build a system that is resilient, not just functional.

Don't let your infrastructure be the bottleneck. Deploy a high-performance K8s node on CoolVDS today and test the latency yourself.