CKAD Services and Networking Practice Question
Which TWO of the following are correct about the ExternalName Service type?
⚠ Common exam trap
A common trap is thinking that ExternalName Services still use selectors or endpoints, but the key point is that ExternalName is a pure DNS-level alias with no pod selection, no load balancing, and no proxy involvement.
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
✓
It maps a Service to a DNS name, not to pods
An ExternalName Service maps a Service to an external DNS name (e.g., `my-service.default.svc.cluster.local` resolves to `api.example.com`) rather than to a set of pods. It does not use selectors or endpoints; instead, it returns a CNAME record pointing to the external name, enabling in-cluster clients to access external services via a stable Kubernetes Service DNS 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.
- ✓
It maps a Service to a DNS name, not to pods
Why this is correct
An ExternalName Service is a DNS-level alias that maps the Service's DNS name to a fully qualified external DNS name rather than to a pod IP. It contains no selector and no Endpoints object, so Kubernetes never routes requests to pods. The mapping is purely for service discovery, letting clients resolve a stable in-cluster name to an external hostname.
- ✗
It provides load balancing across pods
Why it's wrong here
ExternalName Services do not create any backing pods or Endpoints, so they cannot load-balance traffic across pods. Load balancing in Kubernetes is performed by the iptables/ipvs rules that kube-proxy installs for Services with selectors. Because ExternalName has no selectors and no cluster IP, no such proxy rules exist, and DNS returns the external name instead of distributing requests.
- ✗
It selects pods using a label selector
Why it's wrong here
Label selectors are used by ClusterIP, NodePort, and LoadBalancer Services to choose the pods that form the Service's Endpoints. ExternalName deliberately omits a selector and never populates an Endpoints object. Instead of matching pods, it defines an external DNS target to which a CNAME record points. Selecting pods would contradict its purpose of referencing an out-of-cluster resource.
- ✓
It returns a CNAME record in DNS
Why this is correct
When a client queries the cluster's DNS server for an ExternalName Service, the DNS server responds with a CNAME record rather than an A record, pointing to the configured externalDNSName field. This is the mechanism that enables the Service to alias an external hostname inside the cluster's DNS namespace. The client then resolves that CNAME target separately, following the chain to the actual IP addresses.
- ✗
It requires a cloud provider load balancer
Why it's wrong here
An ExternalName Service is purely a DNS construct and does not allocate any cloud load balancer or external IP. Services like the LoadBalancer type rely on a cloud provider controller to provision infrastructure, but ExternalName simply modifies the cluster's DNS zone to emit a CNAME. No cloud-specific integration, health checks, or backend forwarding are involved, so it works in any cluster, including bare-metal and minikube environments.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKAD 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 CKAD exam.