CKA Troubleshooting Practice Question
You are troubleshooting a DNS issue in the cluster. You exec into a pod and run 'nslookup kubernetes.default.svc.cluster.local'. The command returns 'server can't find kubernetes.default.svc.cluster.local: NXDOMAIN'. What is the MOST likely cause?
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
✓
The CoreDNS pod(s) are not running or are misconfigured
NXDOMAIN indicates that the DNS server does not have a record for that name. The most common cause is that the CoreDNS pod(s) are not running or are misconfigured. Option A would cause a timeout not NXDOMAIN. Option B would cause a different error (connection refused). Option D might cause partial resolution but not NXDOMAIN for the entire service name.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The kube-dns service does not exist
Why it's wrong here
If the service does not exist, nslookup would return a 'connection refused' or 'server failure' error, not NXDOMAIN.
- ✗
The pod's /etc/resolv.conf points to an external DNS server instead of the cluster DNS
Why it's wrong here
If it points to an external server, the query would likely succeed or timeout, but not return NXDOMAIN for the cluster domain.
- ✓
The CoreDNS pod(s) are not running or are misconfigured
Why this is correct
If CoreDNS is down, DNS resolution fails with NXDOMAIN because there is no server to answer.
- ✗
The pod's network policy blocks DNS traffic
Why it's wrong here
Network policies typically drop packets, causing timeouts rather than NXDOMAIN.
Visual reference
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
CoreDNS
CoreDNS is a fast, flexible, and pluggable Domain Name System (DNS) server that is often used as the cluster DNS for Kubernetes, translating service names into IP addresses so containers can find each other.
About these practice questions
This CKA question is part of Courseiva's 302-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.