CKA Services & Networking Practice Question
A cluster has multiple namespaces: 'frontend', 'backend', and 'monitoring'. A pod in the 'frontend' namespace needs to reach a Service named 'db-service' in the 'backend' namespace. The 'db-service' Service is of type ClusterIP. Which DNS name should the pod use?
⚠ Common exam trap
The trap here is that candidates often forget the 'svc' subdomain or assume that omitting the namespace works across namespaces, leading them to pick Option A or C, while the correct FQDN must include both namespace and 'svc' for reliable resolution.
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
✓
db-service.backend.svc.cluster.local
Kubernetes DNS resolves services using the format `<service>.<namespace>.svc.cluster.local`. Since the pod is in the 'frontend' namespace and needs to reach 'db-service' in the 'backend' namespace, the fully qualified domain name (FQDN) must include the namespace and the 'svc' subdomain to be resolved by the cluster DNS (CoreDNS).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
db-service.svc.cluster.local
Why it's wrong here
db-service.svc.cluster.local omits the required namespace field between the service name and 'svc'. The standard Kubernetes DNS record is <service>.<namespace>.svc.<cluster-domain>, so without a namespace this name points at service 'db-service' in a namespace literally called 'svc', which does not exist. A Pod in the frontend namespace would therefore receive NXDOMAIN and fail to connect.
- ✗
db-service
Why it's wrong here
db-service is only a resolvable shortcut because a Pod's /etc/resolv.conf includes the local namespace as a DNS search domain, automatically expanding it into db-service.<current-namespace>.svc.cluster.local. If the client Pod runs in 'frontend' and the Service is in 'backend', that automatic expansion resolves to db-service.frontend.svc.cluster.local. Only when working across namespaces do you need an explicit FQDN; short names cannot bridge the namespace boundary.
- ✗
db-service.backend.cluster.local
Why it's wrong here
db-service.backend.cluster.local skips the mandatory 'svc' segment that separates the namespace from the cluster domain in Kubernetes DNS names. The correct path after the namespace is always '.svc.cluster.local' for standard ClusterIP services, so this string would be parsed as service 'db-service' in a namespace 'backend' with an invalid/unknown domain. Without 'svc', CoreDNS treats the name differently and cannot map it to the Service record.
- ✓
db-service.backend.svc.cluster.local
Why this is correct
db-service.backend.svc.cluster.local is the fully qualified domain name Kubernetes automatically creates for the Service named db-service in the backend namespace. Any Pod in any namespace, including frontend, can use this FQDN because it contains every component needed by CoreDNS to locate the ClusterIP. It is the canonical cross-namespace address and avoids relying on search domains or local-only short names.
Visual reference
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Related to this question
Learn chapter
Kubernetes Architecture Overview
Key term
ClusterIP NodePort LoadBalancer
ClusterIP, NodePort, and LoadBalancer are three types of Kubernetes Services that control how traffic reaches your application pods inside the cluster or from outside.
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.
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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.