Configure Multus CNI in Kubernetes: A Detailed Guide

How to Configure Multus CNI in Kubernetes

Configuring Multus CNI (Container Network Interface) in Kubernetes enables you to attach multiple network interfaces to your pods, providing better network management and isolation. This tutorial will guide you through the steps necessary to install and configure Multus CNI in your Kubernetes cluster.

Prerequisites

Basic understanding of Kubernetes and CNI plugins.
A running Kubernetes cluster (version 1.16+).
kubectl configured to interact with your cluster.
Access to the internet to download necessary components.

Step-by-Step Configuration

Step 1: Installing Multus CNI

First, you will need to deploy the Multus CNI plugin. Execute the following command to deploy the Multus DaemonSet on your Kubernetes cluster:

kubectl apply -f https://raw.githubusercontent.com/k8snetworkplumbingwg/multus-cni/master/images/multus-daemonset.yml

This command downloads and applies the Multus DaemonSet configuration from the GitHub repository.

Step 2: Verify Installation

Verify that the Multus pods are running correctly using the command:

kubectl get pods --namespace=kube-system

Look for pods with ‘multus’ in their name, and make sure their status is set to Running.

Step 3: Configure Multus for Additional Networks

You’ll need to create additional network configurations. This can be done by defining Custom Resource Definitions (CRDs). Below is an example of a NetworkAttachmentDefinition:

apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: second-network
  namespace: my-namespace
spec:
  config: '{
      "cniVersion": "0.3.1",
      "type": "macvlan",
      "master": "eth0",
      "mode": "bridge",
      "ipam": {
        "type": "host-local",
        "subnet": "192.168.1.0/24",
        "rangeStart": "192.168.1.100",
        "rangeEnd": "192.168.1.200",
        "gateway": "192.168.1.1"
      }
    }'

Applying this configuration allows you to attach a second network to your pods.

Step 4: Deploy a Pod to Use Multiple Networks

Here’s a sample pod configuration that uses multiple networks:

apiVersion: v1
kind: Pod
metadata:
  name: my-multus-pod
  annotations:
    k8s.v1.cni.cncf.io/networks: '["default", "second-network"]'
spec:
  containers:
  - name: my-container
    image: busybox
    command: ["sleep", "3600"]

The annotations field indicates the networks that the pod should connect to.

Troubleshooting

Ensure Pods Are Scheduled: If pods aren’t starting, ensure that Multus is properly set up on all nodes.
Check Network Configurations: Incorrect network configurations in NetworkAttachmentDefinition can cause networking failures.
View Pod Logs: Use kubectl logs to diagnose issues in Multus or other networking pods.

Summary Checklist

Install Multus CNI through the official DaemonSet manifest.
Verify Multus pods are running.
Create additional network configurations using CRDs.
Deploy pods with multiple network interfaces.
Troubleshoot using kubectl commands and logs.

For further insight, you can explore other networking configurations like Calico and Flannel from our previous guides, such as how to install Flannel networking on Kubernetes.