Lecture: Networking Configurations in a Kubernetes Cluster

In this lecture, we will cover the networking configurations required on the master and worker nodes in a Kubernetes cluster. The Kubernetes cluster consists of master and worker nodes, each requiring specific network setups.

Network Requirements for Nodes

  1. Network Interfaces:

    • Each node must have at least one interface connected to a network.
    • Each interface must have a configured address.

  2. Host Configuration:

    • Each host must have a unique hostname and a unique MAC address.
    • Ensure uniqueness, especially if VMs were cloned from existing ones.

Docker Networking

Port Configurations

Various ports must be opened for different components in the control plane:

  • API Server: Port 6443
    • Accessed by worker nodes, kube control tool, external users, and all other control plane components.

Docker Networking

  • Kubelet: Port 10250
    • Kubelets can be present on both master and worker nodes.
  • Kube Scheduler: Port 10259
  • Kube Controller Manager: Port 10257
  • Service Exposure: Ports 30000-32767
  • ETCD Server: Port 2379

Docker Networking

Multiple Master Nodes:

  • Open the same ports as a single master node.
  • Additional Port 2380 for ETCD clients to communicate.

Docker Networking

These port configurations are crucial and listed in the Kubernetes documentation. https://kubernetes.io/docs/reference/networking/ports-and-protocols/

Therefore, when setting up networking for your nodes, consider the following:

  • Configuring firewalls, IP table rules, or network security groups in cloud environments like GCP, Azure, or AWS.
  • Ensuring these configurations to troubleshoot networking issues.