CKA Services and Networking Practice Question
What is the default DNS name for a Service named 'my-svc' in namespace 'my-ns'?
⚠ Common exam trap
The trap here is that candidates often forget the 'svc' subdomain or the namespace component, mistakenly thinking the Service name alone (e.g., 'my-svc.cluster.local') or just the namespace (e.g., 'my-svc.my-ns.cluster.local') is sufficient, while Kubernetes strictly requires the full `<service>.<namespace>.svc.cluster.local` format for cross-namespace DNS 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
✓
my-svc.my-ns.svc.cluster.local
Kubernetes constructs the default DNS name for a Service using the format `<service-name>.<namespace>.svc.cluster.local`. This is defined by the cluster DNS specification (CoreDNS or kube-dns) and allows Pods to resolve the Service by its fully qualified domain name (FQDN) within the cluster. For 'my-svc' in namespace 'my-ns', the FQDN is 'my-svc.my-ns.svc.cluster.local'.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
my-svc.my-ns.svc.cluster.local
Why this is correct
This is the canonical Kubernetes Service Fully Qualified Domain Name (FQDN). The layout is <service-name>.<namespace>.svc.<cluster-domain>, and for a service named my-svc in namespace my-ns, the default cluster domain cluster.local yields my-svc.my-ns.svc.cluster.local. This record is dynamically maintained by CoreDNS and resolves to the service's ClusterIP, allowing deterministic internal access for workloads in any namespace.
- ✗
my-svc.svc.cluster.local
Why it's wrong here
Omitting the namespace is invalid for a Service FQDN because the namespace is a mandatory second left-most label in the DNS name. A query for my-svc.svc.cluster.local is interpreted as a Service named my-svc in an empty or nonexistent namespace context, and Kubernetes DNS never registers records without a namespace segment. Without that segment, the resolver cannot disambiguate which namespace's my-svc Service is requested, so the lookup fails with NXDOMAIN.
- ✗
my-svc.my-ns.cluster.local
Why it's wrong here
The literal label 'svc' is not a placeholder but a fixed subdomain under the namespace that hosts all Kubernetes Service records. Removing it to produce my-svc.my-ns.cluster.local places the query one level high in the DNS hierarchy, and no wildcard or prefix record exists to match that name. Since the name lies outside the service DNS subtree, CoreDNS will not find an A/AAAA record for it, even if a Service named my-svc exists in the my-ns namespace.
- ✗
my-svc.cluster.local
Why it's wrong here
This name drops both the namespace and the svc component, placing my-svc at the cluster root, where only cluster-level records—such as the CoreDNS service itself—may live. Kubernetes has no mechanism to register Service names directly under <service-name>.cluster.local; every Service is scoped exactly one namespace deep. Even if a Service were in the default namespace, the correct name is my-svc.default.svc.cluster.local, not my-svc.cluster.local, so this lookup can never match any Service object.
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Related to this question
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Installing Kubernetes with kubeadm
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.
Key term
Network Policies
A Kubernetes resource that controls how pods communicate with each other and with other network endpoints, acting as a firewall for pod-to-pod traffic.
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Written by Johnson Ajibi, MSc IT Security
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