Kubernetes Networking Concepts
⚠️ Work in progress, see "Kubernetes Learning.doc/Kubernetes Networking Concepts".
This page describes various Kubernetes networking aspects, grouped around several high level subjects. It starts by explaining how pods communicate with each other within a Kubernetes cluster. This is the Pod Networking section. Service Networking section explains with how Kubernetes services use a stable virtual IP address to offer access to a pool equivalent pods, all of which may come and go individually. In these two sections will be mainly discussing about IP addresses and routing. Naming and DNS, including how service names are mapped to service IP addresses, is discussed in the DNS Support section. Finally, we'll discuss about how external traffic reaches the pods, in the Ingress section.
Pod NetworkingAlso see:
Every pod in the Kubernetes cluster has its own IP address, which is routable on the pod network, so every pod on the pod network can talk directly to every other pod.
Cluster IP Address
ClusterIP services expose stable Cluster IP addresses.
Flannel is the default network plugin that comes with Kubespray. Flannel is an L2 overlay network solution. An L2 solution is difficult to troubleshoot due to packet encapsulation. Also, every node in the network is state-heavy (VLANs, tunnels).
Calico is a pure L3 fabric solution. It is also referred to as a network policy engine for Kubernetes.