Day 48: How DNS Works in Kubernetes | CoreDNS, FQDNs, Pods & Services | CKA Course 2025
Day 48: Kubernetes DNS Explained | CKA Course 2025
👉 GitHub Repository: https://github.com/CloudWithVarJosh/C...
👉 CKA 2025 Playlist: • CKA Certification Course 2025
📚 Welcome to Day 48!
In this lecture, we break down DNS in Kubernetes, focusing on how internal service and pod names are resolved using CoreDNS, the default DNS server in most clusters.
We explore how Fully Qualified Domain Names (FQDNs) are structured in Kubernetes, including the role of the cluster.local root domain, and the subdomains used for services, pods, and namespaces. We also go under the hood to analyze the Corefile configuration in CoreDNS, and explain how plugins like kubernetes, pods, and forward work together to enable name resolution.
In addition to real-world examples and cross-namespace behavior, we introduce troubleshooting techniques and common misconfigurations that can break DNS inside a cluster.
📝 What We’ll Cover:
✅ FQDN structure for Services and Pods
✅ How Kubernetes DNS is different from public DNS
✅ CoreDNS plugin breakdown: kubernetes, pods, forward, cache, etc.
✅ Reverse lookups using in-addr.arpa and ip6.arpa
✅ DNS entries for Services vs. Pods vs. StatefulSets
✅ The difference between pods insecure, pods verified, and pods hostname
✅ DNS troubleshooting with nslookup, dig, and /etc/nsswitch.conf
✅ Demo: Real-time inspection of DNS entries and resolution across namespaces
✅ Understanding CoreDNS caching behavior
✅ Best practices for secure pod DNS in production
💡 By the end of this lecture:
You’ll have a deep understanding of how DNS works within a Kubernetes cluster, how CoreDNS is configured, and how to debug DNS issues confidently.
🔗 Stay Connected:
👉 LinkedIn: / varun-joshi-2b516752
👉 GitHub: https://github.com/CloudWithVarJosh
💬 Got questions? Drop them in the comments — I reply to every single one.
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⏰ Timestamps
00:00:00 Introduction
00:00:51 What You Should Know Before This Lecture
00:05:45 Fully Qualified Domain Names (FQDNs) in Kubernetes: Services, Pods, and StatefulSets
00:10:00 DNS Structure in Kubernetes: A Layer-by-Layer Breakdown
00:17:07 How Kubernetes DNS Works: Creation and Resolution Process
00:19:02 Demo 1: Inspecting DNS Records for Services and Pods
00:31:41 Demo 2: DNS Resolution Across Namespaces
00:36:30 Exploring the CoreDNS ConfigMap and Corefile
00:45:02 DNS Troubleshooting Techniques for Kubernetes Clusters
00:49:08 Wrap-Up and What’s Next: Ingress
🔖 Hashtags
#Kubernetes #CKA #CloudWithVarJosh #CKACourse #CKA2025 #CoreDNS #KubernetesDNS #K8sNetworking #PodDNS #StatefulSets #DNSDebugging #DevOps #CloudNative #KubernetesForAdmins #CKAExamPrep #Ingress #K8sTroubleshooting #CKALabs #SRE #ServiceDiscovery #FQDN