What is Container Network Interface (CNI)?

CNI is a specification and set of libraries that define how network connectivity is provided to containers. Kubernetes uses CNI plugins to manage Pod networking, regardless of the container runtime in use—such as containerd, cri-o, or Docker (which relied on the dockershim component, deprecated in Kubernetes v1.20).

Kubernetes uses CNI as its networking interface for managing container networking. CNI plugins are employed to set up networking for Pods, facilitating communication within the cluster. CNI provides a standardized way for different container runtimes to use various networking plugins seamlessly, allowing containers to communicate with each other and the broader network.

CNI plugins themselves are executable files that implement the CNI specification. These plugins handle tasks such as setting up network interfaces, configuring routes, and managing container networking namespaces. Container runtimes interact with...