CKA Services and Networking Practice Question
Which of the following is a valid CNI plugin for Kubernetes networking?
⚠ Common exam trap
Many candidates confuse cluster infrastructure components (etcd, kubelet) or container runtimes (Docker) with CNI plugins, because they are all part of the Kubernetes ecosystem but serve fundamentally different roles.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Calico
Calico is a valid CNI plugin that implements the Container Network Interface specification to provide networking and network policy for Kubernetes clusters. It uses BGP (Border Gateway Protocol) to route packets between nodes and supports overlay or non-overlay networking modes, making it a widely adopted choice for production environments.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Calico
Why this is correct
Calico is a valid Container Network Interface (CNI) plugin that provides networking and network policy for Kubernetes clusters. It implements the CNI specification by configuring routes, assigning IP addresses (via IPAM), and enforcing policy using iptables or eBPF dataplanes, making it one of the most widely adopted CNI plugins in production.
- ✗
etcd
Why it's wrong here
etcd is a distributed key-value store that Kubernetes uses as its backing database for all cluster state, such as configuration, secrets, and object metadata. It does not implement the CNI specification, has no concept of container network interfaces, and serves a completely different purpose in the control plane, so it cannot be used as a CNI plugin.
- ✗
Docker
Why it's wrong here
Docker is a container runtime and platform that historically used its own networking model (e.g., docker bridge) and only later adopted CNI through Docker's libnetwork. In Kubernetes, Docker is used to run containers via the CRI (albeit deprecated with dockershim), but it does not act as a CNI plugin; instead, CNI plugins like Calico or Flannel handle the container networking.
- ✗
Kubelet
Why it's wrong here
Kubelet is a node agent that runs on each worker node and is responsible for managing pods, containers, and their lifecycle, including invoking container runtimes. It communicates with the CNI plugin by executing the plugin's binaries (e.g., for ADD/DEL commands) but it is not itself a plugin; it is the orchestrator side that delegates network setup to true CNI plugins.
Go deeper
Related to this question
Learn chapter
Kubernetes Architecture Overview
Key term
Ingress Resources
Ingress Resources are Kubernetes API objects that manage external access to services inside a cluster, typically HTTP and HTTPS traffic, by defining rules for routing requests based on hostnames and paths.
Key term
CNI Plugins
CNI plugins are modular software components that configure container network interfaces according to the Container Network Interface specification, allowing containers to communicate within a Kubernetes cluster.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKA practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CKA exam.