Today we're going to talk about container network interfaces. The CNI project and CNCF help combine various network technologies and produce a set of plugins that can be switched in and out of Kubernetes clusters through the kubelets to offer different features and use cases. They are a requirement for inter-node networking, and there are many different options and flavors. Some offer VXLAN capabilities, dual stacking, extended Berkeley Packet Filter, logging, etc. But essentially, they're all designed so that you can talk between containers at the base layer. The reason that CNI is popular and why it was necessary is that Kubernetes doesn't provide its own networking implementation, it just defines the model, and it leaves us to fill the gaps and build that model out.