Originally published on the Google Cloud Community blog at https://medium.com/google-cloud/understanding-kubernetes-networking-pods-7117dd28727
This post is going to attempt to demystify the several layers of networking operating in a kubernetes cluster. Kubernetes is a powerful platform embodying many intelligent design choices, but discussing the way things interact can get confusing: pod networks, service networks, cluster IPs, container ports, host ports, node ports… I’ve seen a few eyes glaze over. We mostly talk about these things at work, cutting across all layers at once because something is broken and someone wants it fixed. If you take it a piece at a time and get clear on how each layer works it all makes sense in a rather elegant way.
In order to keep things focused I’m going to split the post into three parts. This first part will look at containers and pods. The second will examine services, which are the abstraction layer that allows pods to be ephemeral. The last post will look at ingress and getting traffic to your pods from outside the cluster. A few disclaimers first. This post isn’t intended to be a basic intro to containers, kubernetes or pods. To learn more about how containers work see this overview from Docker. A high level overview of kubernetes can be found here, and an overview of pods specifically is here. Lastly a basic familiarity with networking and IP address spaces will be helpful.
