Container Network Interface (CNI) in Kubernetes: An Introduction

The Container Network Interface (CNI) in Kubernetes ensures proper network configuration and pod connectivity within the cluster and to the internet. The CNI plugin, consisting of an executable and a daemon, is responsible for IP address management, routing, and network configuration. The post explains how a CNI plugin operates, detailing its role from pod creation in Kubernetes to setting up network namespaces, virtual ethernet pairs, and necessary IP and routing configurations. The article also includes a demonstration of a simple CNI implementation in Go and Bash, tested in a Canonical Kubernetes cluster.