CKA Certification Course 2025 - Day 47: Kubernetes Network Policies Explained with Real-World Demo | CKA Course 2025

Day 47: Kubernetes Network Policies Explained with Real-World Demo | CKA Course 2025 👉 GitHub Repository: https://github.com/CloudWithVarJosh/CKA-Certification-Course-2025 👉 CKA 2025 Playlist: https://youtube.com/playlist?list=PLmPit9IIdzwRjqD-l_sZBDdPlcSfKqpAt&si=1JNRkoNa75AOJx0o 📚 Welcome to Day 47! In this session, we take a deep dive into Kubernetes Network Policies — a critical security mechanism that controls pod-to-pod communication within your cluster. While Kubernetes offers a flat network model by default, real-world production environments demand isolation and traffic boundaries. That's where NetworkPolicies come in. We walk through a hands-on, real-world 3-tier application demo (frontend, backend, database) and apply ingress and egress rules to enforce least privilege access. We also unpack how policy enforcement depends on the CNI plugin, demystify selector logic (AND vs OR), and highlight common pitfalls that often go unnoticed. 📝 What We’ll Cover: ✅ Why default Kubernetes networking is insecure ✅ What are NetworkPolicies and how they work (L3/L4 control) ✅ Understanding Ingress and Egress in detail ✅ Stateful behavior of NetworkPolicies (like AWS Security Groups) ✅ Role of CNI plugins like Calico in policy enforcement ✅ Selector logic: podSelector vs namespaceSelector and their combinations ✅ Common mistakes with overly broad selectors ✅ DNS egress: Why it's needed and how to restrict it safely ✅ Real-world Demo: Enforcing strict pod communication boundaries ✅ Practice Task: Namespace-level isolation ✅ When to use ipBlock and external access control 💡 By the end of this lecture: You’ll confidently design and apply Kubernetes NetworkPolicies that reflect production-ready traffic patterns, isolate workloads, and minimize lateral movement inside your clusters. 🔗 Stay Connected: 👉 LinkedIn: https://linkedin.com/in/varun-joshi-2b516752 👉 GitHub: https://github.com/CloudWithVarJosh 💬 Got questions? Drop them in the comments — I reply to every single one. 👍 Like, share, and subscribe to follow the entire CKA 2025 series! ⏰ Timestamps 00:00:00 - Introduction 00:00:50 - Why We Need Network Policies 00:04:48 - What Are Network Policies? 00:10:57 - Ingress vs Egress Explained 00:15:44 - Designing Ingress and Egress Rules 00:21:54 - Demo Overview: Enforcing Least Privilege 00:22:11 - Step 1: Setting Up KIND with Calico 00:29:45 - Step 2: Deploying Frontend, Backend, and DB 00:37:27 - Step 3: Installing Telnet and Testing Full Connectivity 00:43:53 - Step 4: Applying and Verifying NetworkPolicies 01:12:24 - Practice Task: Namespace Isolation Challenge 01:12:55 - AND vs OR in NetworkPolicy Selectors 01:13:38 - Outro and What’s Next (DNS in Kubernetes) 🔖 Hashtags #Kubernetes #CKA #CloudWithVarJosh #CKACourse #CKA2025 #NetworkPolicies #K8sSecurity #Calico #CNIs #PodSecurity #KubernetesDemo #LeastPrivilege #K8sNetworking #IngressEgress #DevOps #CloudNative #CKAExamPrep #KubernetesBestPractices #CKALabs #SRE #KubernetesForAdmins