CKAD Services and Networking Practice Question
An admin creates a Service without a selector. Which of the following is true about such a Service?
⚠ Common exam trap
Candidates often assume a Service must have a selector to function, but Kubernetes allows headless or manually-endpointed Services, and the exam tests whether you know that endpoints can be created independently of selectors.
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 admin must manually create an Endpoints object with the desired IPs.
When a Service is created without a selector, Kubernetes does not automatically manage its endpoints. The admin must manually create an Endpoints object (or use an EndpointSlice) that lists the IP addresses and ports to which the Service should route traffic. This allows the Service to direct traffic to external resources, such as databases running outside the cluster, or to specific pods not matching a label selector.
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 Service will use the default ClusterIP and route to all pods in the cluster.
Why it's wrong here
This is wrong because while a selectorless Service does get a ClusterIP (the service still gets a virtual IP), it does not automatically route to all pods. Without a selector, the Service controller does not create or update an Endpoints object. Traffic sent to the ClusterIP will have no backend endpoints unless one is manually defined, so it will be dropped. The absence of a selector means no pod is automatically targeted; routing requires an explicit Endpoints resource (or external endpoints) to direct traffic.
- ✗
The Service will automatically route traffic to all pods in the namespace.
Why it's wrong here
This is wrong because a Service without a selector has no mechanism to discover pods. Kubernetes does not automatically associate a Service with pods solely based on namespace; the selector is what defines the pod label set to target. Since there is no selector, the Service controller takes no action to populate Endpoints, so it cannot route to any pods in the namespace. The Service IP may be allocated but no load balancing backend exists.
- ✓
The admin must manually create an Endpoints object with the desired IPs.
Why this is correct
This is correct because a Service without a selector needs a separately-created Endpoints object to define the backend IP addresses and ports. The admin can create an Endpoints resource with the same name as the Service, listing the IPs and port numbers where traffic should be forwarded. This pattern is commonly used to route to external databases, legacy systems, or services outside the cluster. Once the Endpoints exist, the Service becomes routable.
- ✗
The Service will not have any endpoints until a selector is added.
Why it's wrong here
This is wrong because it ignores the possibility of manually creating an Endpoints resource even without a selector. A selector is not the only way to provide endpoints; the admin can define an Endpoints object explicitly. The Service controller does not create endpoints for selectorless services, but manual endpoints can be created at any time. The statement implies a selector is required, which is false in this context.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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