Understanding Kubernetes Networking

Introduction to Kubernetes Networking ⇒

Networking is a fundamental aspect of Kubernetes, enabling communication between containers, pods, and external services. Unlike traditional networking models, Kubernetes provides a built-in networking approach that eliminates the need for complex configurations like port mapping.

Kubernetes networking solves four main challenges:

1. Container-to-Container Communication (Within the Same Pod)
   • Containers within the same pod communicate using the loopback interface (localhost).
   • Since they share the same network namespace, they can communicate as if they were running on the same machine.
2. Pod-to-Pod Communication (Within the Cluster)
   • Pods need to communicate across different nodes inside the Kubernetes cluster.
   • Kubernetes provides a flat network where every pod gets a unique IP address.
   • This eliminates the need for NAT (Network Address Translation), making it easy for pods to interact without additional network configurations.
3. Pod-to-Service Communication
   • A Service in Kubernetes acts as an abstraction that provides a stable IP and DNS name for a group of pods.
   • This is crucial because pods are dynamic and can be replaced or rescheduled, causing their IP addresses to change.
   • Services ensure that requests are routed correctly to healthy pods.
4. External-to-Service Communication (Ingress and External Services)
   • When an application running inside a Kubernetes cluster needs to be accessed from outside, Kubernetes provides mechanisms like NodePort, LoadBalancer, and Ingress Controllers to expose it to external users.

How Two Containers Communicate Within the Same Pod? ⇒

When multiple containers are running inside the same pod, they share the same network namespace. This means:

• They can communicate through localhost (loopback network).
• They can directly access each other's exposed ports without needing additional networking configurations.

For example, if one container runs an Apache web server on port 80, another container inside the same pod can access it by simply calling localhost:80.

Hands-on Lab: Setting Up Kubernetes Networking ⇒

This lab will help you understand how Kubernetes networking works by setting up two containers inside a pod and enabling communication between them.

Step 1: Set Up an AWS Instance for Minikube

Before running Minikube, we need a virtual machine (VM) to act as our Kubernetes node. We will use an AWS T2-Medium instance.

1. Launch an AWS EC2 Instance
   • Choose Ubuntu as the operating system.
   • Select an instance type T2-Medium (2 vCPUs, 4GB RAM).
   • Configure security groups to allow SSH access.