From Linux Bridges and CNI to Services and CoreDNS — Everything You Need to Know
If there is one topic that separates a junior from a pro, it’s networking.
In Kubernetes, networking is a layered system of abstractions; you need to understand what’s happening at every layer.
When a pod can’t reach a service, is it a DNS issue? A Network Policy? A problem with the CNI?
This article will give you the mental model to answer those questions. We’ll start from the absolute basics of Linux networking and build our way up to the magic of Kubernetes Services.
Part 1: The Foundation — Linux Networking
Kubernetes doesn’t reinvent networking; it masterfully orchestrates existing Linux features.
Network Namespaces (netns)
The fundamental technology that provides network isolation for containers is the network namespace. Each namespace gets its own private set of network resources: IP addresses, routing tables, and firewall rules.
A pod’s container doesn’t see the host’s network interfaces; it lives in its own netns. You can create and manage…
