Kubernetes Networking Guide

Understanding Kubernetes Networking Concepts

Kubernetes Networking Fundamentals

Kubernetes networking enables communication between containers, pods, services, and external clients. Understanding these networking concepts is crucial for deploying and managing applications in Kubernetes.

Core Networking Concepts

Container Communication

All containers within a pod can communicate with each other via localhost.

Pod Communication

All pods can communicate with each other without NAT, regardless of which node they're on.

Node-Pod Communication

All nodes can communicate with all pods without NAT restrictions.

Pod IP Addresses

Pods are given an IP address that is ephemeral - it changes when pods are recreated.

Service IP Addresses

Services are given a persistent IP address that remains stable throughout their lifecycle.

Inter-Pod Communication

Pod Internal Communication

Pod IP Address

Container 1

localhost:port

Container 2

localhost:port

Container 3

localhost:port

Container 4

localhost:port

Containers within the same pod share the same network namespace and can communicate with each other using localhost and different ports. They also share the same IP address.

Key Points:

  • Containers in a pod share the same network namespace
  • They can communicate via localhost and different ports
  • All containers in a pod have the same IP address
  • This enables efficient inter-process communication

External Access to Applications

External Access Architecture

Load Balancer

↓

Service

↓

Pod

Pod

Pod

↑

Cloud Provider Service

How External Access Works:

  1. External clients connect through a LoadBalancer service
  2. The load balancer distributes traffic to the Kubernetes service
  3. The service routes traffic to available pods based on selectors
  4. Cloud provider services integrate with Kubernetes to provide external IPs