KCNA Container Orchestration Practice Question
A Service of type ClusterIP is created for a Deployment, but Pods in other namespaces cannot reach it. What is the most likely cause?
⚠ Common exam trap
A common mix-up: candidates assume DNS works globally across namespaces with short names, but Kubernetes DNS only resolves short names within the same namespace by default, requiring the namespace suffix for cross-namespace access.
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 Pods in other namespaces are using the short Service name without the namespace suffix
The most likely cause is that Pods in other namespaces are using the short Service name (e.g., `my-service`) without appending the namespace suffix (e.g., `my-service.other-namespace.svc.cluster.local`). Kubernetes DNS resolves short names only within the same namespace; cross-namespace resolution requires the fully qualified domain name (FQDN) or at least the `<service>.<namespace>.svc` form. Without this, the DNS lookup fails, making the Service unreachable from other namespaces.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
NetworkPolicies are blocking cross-namespace traffic
Why it's wrong here
While possible, the most likely cause is DNS naming.
- ✓
The Pods in other namespaces are using the short Service name without the namespace suffix
Why this is correct
Cross-namespace access requires the full DNS name including the namespace.
- ✗
The Service is not publishing the correct port
Why it's wrong here
Port mismatch would cause connection failure, not DNS resolution issues across namespaces.
- ✗
The Service selector does not match the Pod labels
Why it's wrong here
If the selector didn't match, the Service wouldn't work within the namespace either.
Visual reference
Go deeper
Related to this question
Learn chapter
Kubernetes Overview and Core Components
Key term
ReplicaSet and Replication
A ReplicaSet ensures a specified number of identical pod instances are running at all times in Kubernetes, using replication to maintain availability and stability.
Key term
Namespaces
A Namespace in Kubernetes is a virtual cluster within a physical cluster that allows you to organize and isolate resources, like an apartment building with separate units for different tenants.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This KCNA 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 KCNA exam.