Using Multus

3 Using Multus

This section contains a basic test to verify you can create a Kubernetes application that uses Multus. This example verifies you can use Multus to create a second network interface on a pod, which uses a network created with a NetworkAttachmentDefinitions CRD.

To create a second network interface:

On a control plane node, create a YAML file named nad-bridge.yaml that contains a NetworkAttachmentDefinition CRD for a bridged connection. Create a YAML file with the following contents:

apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: bridge-conf
spec:
  config: '{
      "cniVersion": "0.3.1",
      "type": "bridge",
      "bridge": "mybr0",
      "ipam": {
          "type": "host-local",
          "subnet": "192.168.12.0/24",
          "rangeStart": "192.168.12.10",
          "rangeEnd": "192.168.12.200"
      }
    }'

Use the kubectl apply command to create the NetworkAttachmentDefinition with the file:
```
kubectl apply -f nad-bridge.yaml
```
The NetworkAttachmentDefinition is created.
You can verify the NetworkAttachmentDefinition is created using:
```
kubectl get network-attachment-definitions
```
The output looks similar to:
```
NAME          AGE
bridge-conf   2m
```
To display more information about the NetworkAttachmentDefinition, use the kubectl describe command, for example:
```
kubectl describe network-attachment-definitions bridge-conf 
```

Create a YAML file named multus-pod.yaml to create a pod running Oracle Linux 9 that uses the bridge-conf network, with the following contents:

apiVersion: v1
kind: Pod
metadata:
  name: samplepod
  annotations:
    k8s.v1.cni.cncf.io/networks: bridge-conf
spec:
  containers:
  - name: samplepod
    command: ["/bin/sh", "-c", "trap : TERM INT; sleep infinity & wait"]
    image: container-registry.oracle.com/os/oraclelinux:9-slim

Start the pod using the kubectl command:
```
kubectl apply -f multus-pod.yaml
```

You can see the pod is created and running using:

kubectl get pods

The output looks similar to:

NAME                   READY   STATUS    RESTARTS   AGE
samplepod              1/1     Running   0          1m

Use the kubectl describe command to show the IP address assigned to the network interfaces of the multus-nginx-pod:

kubectl describe pod samplepod

The output looks similar to:

Name:             samplepod
Namespace:        default
...
Annotations:      k8s.v1.cni.cncf.io/network-status:
                    [{
                        "name": "cbr0",
                        "interface": "eth0",
                        "ips": [
                            "10.244.3.4"
                        ],
                        "mac": "86:e7:82:28:58:59",
                        "default": true,
                        "dns": {},
                        "gateway": [
                            "10.244.3.1"
                        ]
                    },{
                        "name": "default/bridge-conf",
                        "interface": "net1",
                        "ips": [
                            "192.168.12.10"
                        ],
                        "mac": "ca:bb:74:ca:9c:10",
                        "dns": {}
                    }]
                  k8s.v1.cni.cncf.io/networks: bridge-conf
...

In this example, you can see the net1 network interface is using the bridge-conf network, and has the IP address of 192.168.12.10.

You can delete the resources creating in this example using:

kubectl delete pod samplepod
kubectl delete network-attachment-definitions bridge-conf