Myth 3: Kubernetes Networking Works Fine Without a CNI Plugin

You set up a Production Kubernetes cluster, deploy some pods, and… nothing. They can't talk to each other, You search Stack Overflow, try restarting pods, but nothing works, Finally, you realize networking is broken, and some pods are stuck in "ContainerCreating" state. You check the logs and see:

NetworkPluginNotReady: CNI plugin not initialized

So, What might be wrong?

Why This Myth Exists?

1. Local environments create an illusion – Some Kubernetes distributions (like Minikube, k3s, and kind) include built-in networking, making it seem like a CNI is optional. Since these setups "just work" out of the box, users may not realize a CNI is missing in a standard cluster.
2. Kubernetes does not bundle a default CNI – Unlike other components (like the scheduler or API server), Kubernetes does not ship with a preinstalled CNI. This can mislead users into thinking networking is an add-on rather than a fundamental requirement.
3. Single-node clusters work without a CNI – On a single-node cluster, all pods can share the host’s networking stack. This makes basic pod communication seem functional, masking the fact that a proper CNI is required for multi-node networking, pod IP assignment, and policies.

The Reality:

A CNI (Container Network Interface) plugin is essential for Production Grade Kubernetes networking—without it, core networking functionalities break.

• Pod-to-pod communication depends on CNI – Kubernetes does not manage networking by itself; it relies on a CNI to assign IP addresses and enable connectivity between pods, especially across nodes.

• Multi-node clusters require a CNI – Without a CNI, pods on different nodes cannot communicate because Kubernetes does not provide an internal networking layer.

• Critical Kubernetes features won’t work – Services, network policies, and pod IP management all rely on a CNI. Without it, pods may remain stuck in the ContainerCreating state, and basic networking between workloads will fail.

Even though local setups like k3s and Minikube may seem to work without a visible CNI,this is because they embed lightweight networking solutions. In a standard Kubernetes cluster, a CNI is mandatory for networking to function.

Experiment & Validate

Step 1: Check Pod Status Without a CNI If a Kubernetes cluster is deployed without a CNI, pods will be stuck in the ContainerCreating state. Run:

kubectl get pods -A

Example output:

NAMESPACE     NAME                          READY   STATUS              RESTARTS   AGE
kube-system   coredns-78fcd69978-2v7        0/1     ContainerCreating   0          10m
kube-system   coredns-78fcd69978-s7jxp      0/1     ContainerCreating   0          10m

Step 2: Check Node Conditions Inspect the node description to verify networking errors:

kubectl describe node <node-name>

You'll likely see an error like:

NetworkPluginNotReady: network plugin is not ready: cni plugin not initialized

Step 3: Verify Missing Network Interfaces Kubernetes assigns pod IPs through the CNI. If no CNI is installed, pods won’t receive IPs:

kubectl get pods -o wide

If the IP column is empty or missing, it confirms that pod networking is broken due to a missing CNI.

Key Takeaways

• Kubernetes delegates networking to a CNI, making it a required component.
• Without a CNI, pods won’t get IPs, and multi-node clusters won’t work.
• Some local environments provide built-in networking, making CNIs seem optional..
• Always verify a CNI is installed to ensure Kubernetes networking works as expected.