Myth 1: kube-proxy assign IP address to Pods

A common belief among Kubernetes users is that kube-proxy is responsible for assigning IP addresses to pods. After all, it manages networking rules and enables communication between services—so it must be the component handling pod IPs, right?

Why Does This Myth Exist?

1. Kube-proxy’s prominent role in networking: Kube-proxy is integral to service-level networking in Kubernetes. Since it manages traffic routing between services and uses iptables, many assume it also handles pod-level networking, including IP assignment.
2. Confusion with iptables: Kube-proxy’s involvement with iptables and traffic forwarding may create the impression that it manages all networking tasks, including assigning IPs to pods.
3. Misunderstanding of Kubernetes components: Newcomers to Kubernetes often see kube-proxy running in the cluster and mistakenly believe it is responsible for all networking-related operations, including pod IP allocation.

The Reality

• Pod IP allocation is the responsibility of the CNI (Container Network Interface) plugin, not kube-proxy. The CNI is responsible for assigning network interfaces and IP addresses to each pod when they are created.
• Kube-proxy’s role is service-level networking: It ensures traffic reaches the right pods by managing network rules for services, but it does not assign IP addresses to the pods themselves.
• Pods depend on the CNI: If there’s no CNI plugin installed or running, Kubernetes pods won’t receive an IP address, even if kube-proxy is operational.

Experiment & Validate

To verify that kube-proxy is not responsible for pod IP allocation, follow these steps: Step1: Check the IP of an existing pod before disabling kube-proxy: Run the following command to view the pod’s details:

kubectl get pods -o wide

Example output:

NAME          READY STATUS    IP          NODE
nginx-abc123  1/1   Running  10.244.1.2  worker-node-1

Step2: Disable kube-proxy temporarily: Scale down the kube-proxy deployment to zero replicas:

kubectl scale deployment/kube-proxy -n kube-system --replicas=0

Step3: Create a new pod and check if it receives an IP address: Launch a new pod and Then, verify the new pod's details::

kubectl run test-pod --image=nginx --restart=Never
kubectl get pods -o wide

You’ll observe that the new pod still receives an IP address, even with kube-proxy disabled, which demonstrates that CNI, not kube-proxy, is responsible for assigning pod IPs.

Key Takeaways

• Kube-proxy does not assign pod IPs – Pod IP allocation is handled by the CNI plugin, not kube-proxy.
• Kube-proxy’s role is service routing – It manages the traffic routing for services, but not the network configuration or IP assignment for pods.
• Without a CNI plugin, pods will fail to receive IP addresses, regardless of whether kube-proxy is running.
• Always ensure a CNI plugin is installed when setting up Kubernetes to guarantee proper networking functionality for pods.