Testing Connectivity Between Kubernetes Pods with Iperf3

• A running Kubernetes cluster
• The kubectl command-line tool installed on your local machine

In this article, we will show you how to use iperf3 to test the connectivity between Kubernetes pods in your cluster. We will use a Deployment to ensure that iperf3 pods are running on each node in the cluster.

Step 1: Deploy Iperf3 as a DaemonSet

To deploy iperf3 as a Deployment on your Kubernetes cluster, you will need to create a YAML file with the following contents:

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: iperf3-ds
spec:
  selector:
    matchLabels:
      app: iperf3
  template:
    metadata:
      labels:
        app: iperf3
    spec:
      containers:
      - name: iperf3
        image: leodotcloud/swiss-army-knife
        ports:
        - containerPort: 5201

This YAML file creates a Deployment named iperf3-ds of the iperf3 container.

You can then create the DaemonSet by running the following command:

kubectl apply -f iperf3-ds.yaml

Step 2: Verify the DaemonSet

Once the DaemonSet is up and running, you can use the following command to check that iperf3 pods are running on all nodes in the cluster:

kubectl get pods

You should see output similar to the following:

NAME                             READY   STATUS    RESTARTS   AGE
iperf3-ds-5b7f6f5c8-5wcw5   1/1     Running   0          36s
iperf3-ds-5b7f6f5c8-6q4q4   1/1     Running   0          36s
iperf3-ds-5b7f6f5c8-8wnw7   1/1     Running   0          36s

Step 3: Test Connectivity Between Pods

To test the connectivity between pods, you will need to use the pod's IP addresses. You can use the following command to get the IP addresses of the pods:

kubectl get pods -o wide

You should see output similar to the following:

NAME                             READY   STATUS    RESTARTS   AGE    IP            NODE
iperf3-ds-5b7f6f5c8-5wcw5   1/1     Running   0          36s   10.1.0.1      node1
iperf3-ds-5b7f6f5c8-6q4q4   1/1     Running   0          36s   10.1.0.2      node2
iperf3-ds-5b7f6f5c8-8wnw7   1/1     Running   0          36s   10.1.0.3      node3

Once you have the IP addresses of the pods you want to test, you can use the iperf3 command to test the connectivity.

First, choose a pod to run in server mode:

kubectl exec -it <pod-name> -- iperf3 -s -p 12345

Second, choose a pod to run in client mode:

kubectl exec -it <pod-name> -- iperf3 -c <server pod IP address> -p 12345

The iperf3 command will output the network performance statistics, including the bandwidth, packet loss, and jitter.

This is an example output from a test cluster; please note that due to the various layers of networking involved, there is a performance impact that is expected:

Connecting to host 10.42.0.36, port 12345
[  4] local 10.42.0.37 port 45568 connected to 10.42.0.36 port 12345
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec  2.23 GBytes  19.1 Gbits/sec  300   2.88 MBytes       
[  4]   1.00-2.00   sec  2.49 GBytes  21.4 Gbits/sec  737   1.58 MBytes       
[  4]   2.00-3.00   sec  2.42 GBytes  20.8 Gbits/sec  524   2.33 MBytes       
[  4]   3.00-4.00   sec  2.17 GBytes  18.6 Gbits/sec  248   2.41 MBytes       
[  4]   4.00-5.00   sec  2.25 GBytes  19.3 Gbits/sec  151   2.45 MBytes       
[  4]   5.00-6.00   sec  2.36 GBytes  20.2 Gbits/sec   73   3.00 MBytes       
[  4]   6.00-7.00   sec  2.40 GBytes  20.6 Gbits/sec  181   2.84 MBytes       
[  4]   7.00-8.00   sec  2.29 GBytes  19.7 Gbits/sec   73   2.64 MBytes       
[  4]   8.00-9.00   sec  2.35 GBytes  20.2 Gbits/sec  110   2.44 MBytes       
[  4]   9.00-10.00  sec  2.27 GBytes  19.5 Gbits/sec  167   2.43 MBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  23.2 GBytes  19.9 Gbits/sec  2564             sender
[  4]   0.00-10.00  sec  23.2 GBytes  19.9 Gbits/sec                  receiver