Setting Up Kubernetes Networking with Weave Net

The Kubernetes networking model creates a virtual network that is accessible to all pods within the cluster. Weave Net is one of several tools that provide an implementation of the Kubernetes networking model. In this learning activity, you will learn how to configure a Kubernetes pod network using Weave Net. After completing the activity, you will have hands-on experience implementing networking within a Kubernetes cluster.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Enable IP forwarding on all worker nodes.

In order for Weave Net to work, you need to make sure IP forwarding is enabled on the worker nodes. Enable it by running the following on both workers:

sudo sysctl net.ipv4.conf.all.forwarding=1

echo "net.ipv4.conf.all.forwarding=1" | sudo tee -a /etc/sysctl.conf

Install Weave Net in the cluster.

Do the following on the controller server:

Install Weave Net using a configuration from Weaveworks like this:

kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d 'n')&env.IPALLOC_RANGE=10.200.0.0/16"

Verify that everything is working:

kubectl get pods -n kube-system

This should return two weave-net pods and look something like this:

NAME              READY     STATUS    RESTARTS   AGE
weave-net-m69xq   2/2       Running   0          11s
weave-net-vmb2n   2/2       Running   0          11s

Spin up some pods to test the networking functionality:

a. First, create an Nginx deployment with 2 replicas:

cat << EOF | kubectl apply --kubeconfig admin.kubeconfig -f -
apiVersion: apps/v1
kind: Deployment
metadata:
 name: nginx
spec:
 selector:
   matchLabels:
     run: nginx
 replicas: 2
 template:
   metadata:
     labels:
       run: nginx
   spec:
     containers:
     - name: my-nginx
       image: nginx
       ports:
       - containerPort: 80
EOF

b. Next, create a service for that deployment so that we can test connectivity to services as well:

kubectl expose deployment/nginx

c. Start up another pod. We will use this pod to test our networking. We will test whether we can connect to the other pods and services from this pod.

kubectl run busybox --image=radial/busyboxplus:curl --command -- sleep 3600

POD_NAME=$(kubectl get pods -l run=busybox -o jsonpath="{.items[0].metadata.name}")

d. Get the IP addresses of our two nginx pods:

kubectl get ep nginx

There should be two IP addresses listed under ENDPOINTS. For example:

NAME      ENDPOINTS                       AGE
nginx     10.200.0.2:80,10.200.128.1:80   50m

Make sure the busybox pod can connect to the nginx pods on both of those IP addresses.
```
kubectl exec $POD_NAME -- curl <first nginx pod IP address>
```
```
kubectl exec $POD_NAME -- curl <second nginx pod IP address>
```
Both commands should return some HTML with the title "Welcome to Nginx!" This means that we can successfully connect to other pods.

Now let’s verify that we can connect to services.

kubectl get svc

This should display the IP address for our Nginx service. For example, in this case, the IP is 10.32.0.54:

NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.32.0.1    <none>        443/TCP   1h
nginx        ClusterIP   10.32.0.54   <none>        80/TCP    53m

Check that we can access the service from the busybox pod.
```
kubectl exec $POD_NAME -- curl <nginx service IP address>
```
This should also return HTML with the title "Welcome to nginx!"

Getting this response means that we have successfully reached the Nginx service from inside a pod and that our networking configuration is working!

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Setting Up Kubernetes Networking with Weave Net

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