Kubernetes Networking Explained: Pods, Services, Ingress, and Network Policies

Kubernetes networking is one of the most misunderstood parts of running containerized workloads. A pod can reach another pod by IP — but why does that stop working after a deployment? A service exists and resolves in DNS — but traffic isn't arriving at the application. An Ingress resource is configured — but requests return 502. These puzzles are common and they stem from the same root: Kubernetes networking has several distinct layers, each solving a different problem, and it's easy to conflate them. This article walks through how Kubernetes networking actually works at each layer — from pod networking to services to Ingress to network policy — so the next time something breaks, you have a mental model to reason from. The fundamental promise: flat pod networking Kubernetes makes one core promise about networking: every pod can communicate directly with every other pod in the cluster without NAT. Every pod gets a real IP address from the cluster's pod CIDR range, and those IPs are routable between pods regardless of which node they're running on. This is not something Kubernetes itself implements. It's a contract that every Kubernetes-conformant CNI (Container Network Interface) plugin must fulfill. When you install Calico, Cilium, Flannel, Weave, or any other CNI, you're installing the component that actually creates this flat network. The mechanism varies — Flannel uses VXLAN overlays, Calico can use BGP for direct routing, Cilium uses eBPF — but the result is the same: pod-to-pod communication without NAT. Here's what a pod's network namespace looks like: $ kubectl exec -it my-pod -- ip addr 1: lo: ... 3: eth0@if12: ... inet 10.244.1.15/24 brd 10.244.1.255 scope global eth0 $ kubectl exec -it my-pod -- ip route default via 10.244.1.1 dev eth0 10.244.0.0/16 via 10.244.1.1 dev eth0 The pod has an IP ( 10.244.1.15 ) on a /24 subnet. The node this pod runs on has an IP from the same range — or a different /24 within the same /16. Traffic from this pod to 10.244.2.8 (