Kubernetes Networking Deep Dive

Kubernetes networking is one of the most complex aspects of the platform. Understanding how containers communicate within and across clusters is crucial for building robust applications.

Kubernetes Networking Model

Kubernetes follows a flat networking model where:

• Every pod gets its own IP address
• Pods can communicate with each other without NAT
• Agents (kubelet) on nodes can communicate with all pods

Core Networking Concepts

Pod Networking

• Each pod has its own network namespace
• Containers in a pod share the same network stack
• Pod IPs are routable within the cluster

Service Networking

• Services provide stable endpoints for pods
• ClusterIP, NodePort, LoadBalancer, and ExternalName types
• kube-proxy handles service routing

Network Policies

• Define rules for pod-to-pod communication
• Implement network segmentation
• Control ingress and egress traffic

CNI (Container Network Interface)

CNI plugins provide the actual networking implementation:

• **Calico**: Policy-driven networking
• **Flannel**: Simple overlay network
• **Weave**: Encrypted networking
• **Cilium**: eBPF-based networking

Service Discovery

Kubernetes provides DNS-based service discovery:

• Services get DNS names: `service-name.namespace.svc.cluster.local`
• Pods can resolve services by name
• Headless services for direct pod access

Network Performance Optimization

1. **Choose the right CNI**: Consider your performance requirements
2. **Use host networking**: For latency-sensitive applications
3. **Optimize service mesh**: If using Istio or Linkerd
4. **Network policies**: Balance security and performance
5. **Monitor network metrics**: Use tools like Prometheus

Troubleshooting

Common networking issues:

• DNS resolution problems
• Service connectivity
• Network policy blocking traffic
• CNI plugin failures

Use kubectl commands and network debugging tools to diagnose issues.