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Manually Testing an IPv6 Kubernetes Cluster With an IPv6-Enabled, Nginx-based Replicated Service

These instructions show how you can manually test an IPv6-only Kubernetes cluster by instantiating an IPv6-enabled, Nginx-based replicated service on an IPv6-only Kubernetes cluster, using the associated YAML files in this repo.

Dockerfile for a Dual-Stack NGINX Server

The standard nginx container image that is available on Dockerhub is configured to listen on port 80 for IPv4 addresses only. For testing NGINX servers in an IPv6-only or dual-stack cluster, the NGINX configuration needs to be modified so that the server is listening for both IPv4 and IPv6 addresses.

The Dockerfile included here can be used to create an NGINX docker image that listens on both IPv4 and IPv6 addresses. The following dual-stack NGINX docker image has been built using this Dockerfile:

diverdane/nginxdualstack:1.0.0

Downloading the YAML Files

To download the IPv6-enabled, Nginx-based service YAML files, clone this repo:

git clone https://github.com/leblancd/kube-v6.git

Creating the Replication Set

cd into the kube-v6 directory, and run kubectl create:

[root@kube-master kube-v6]# cd kube-v6
No resources found.
[root@kube-master kube-v6]# kubectl create -f nginx_v6
replicationcontroller "nginx-controller" created
service "nginx-service" created
[root@kube-master kube-v6]#

Check Pods

[root@kube-master kube-v6]# kubectl get pods -o wide
NAME                     READY     STATUS    RESTARTS   AGE       IP            NODE
nginx-controller-gknzr   1/1       Running   0          27s       fd00:102::2   kube-minion-2
nginx-controller-kqd7c   1/1       Running   0          27s       fd00:101::2   kube-minion-1
nginx-controller-sdx7w   1/1       Running   0          27s       fd00:102::3   kube-minion-2
nginx-controller-zw565   1/1       Running   0          27s       fd00:101::3   kube-minion-1
[root@kube-master kube-v6]#

Check Services

[root@kube-master kube-v6]# kubectl get svc
NAME            TYPE        CLUSTER-IP          EXTERNAL-IP   PORT(S)          AGE
kubernetes      ClusterIP   fd00:1234::1        <none>        443/TCP          10h
nginx-service   NodePort    fd00:1234::3:b606   <none>        8080:30302/TCP   3m
[root@kube-master kube-v6]#

Curl the Service From a Kubernetes Node

Based on the Cluster-IP and service port indicated in the previous step, curl the service:

[root@kube-master kube-v6]# curl -g [fd00:1234::3:b606]:8080
<!DOCTYPE html>
<html>
<head>
<title>Kubernetes IPv6 nginx</title> 
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx on <span style="color:  #C70039">IPv6</span> Kubernetes!</h1>
<p>Pod: nginx-controller-gknzr</p>
</body>
</html>
[root@kube-master kube-v6]#

Test Random Load-Balancing by Curling the Service Repeatedly

If you curl the service repeatedly, you should see a response from one of the 4 endpoint controllers (randomly):

[root@kube-master kube-v6]# curl -g [fd00:1234::3:b606]:8080 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0  44865      0 --:--:-- --:--:-- --:--:-- 70600
<p>Pod: nginx-controller-gknzr</p>
[root@kube-master kube-v6]# curl -g [fd00:1234::3:b606]:8080 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0  36500      0 --:--:-- --:--:-- --:--:-- 39222
<p>Pod: nginx-controller-zw565</p>
[root@kube-master kube-v6]# curl -g [fd00:1234::3:b606]:8080 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0  44774      0 --:--:-- --:--:-- --:--:-- 50428
<p>Pod: nginx-controller-sdx7w</p>
[root@kube-master kube-v6]#

Test Service Access From a Pod

cd to nginx_v6 directory and start a pod that includes the curl utility:

[root@kube-master kube-v6]# cd nginx_v6
[root@kube-master nginx_v6]# ./pod-curl
If you don't see a command prompt, try pressing enter.
[ root@test-curl:/ ]$

Curl the service's endpoints (using IPs from prior 'kubectl get pods -o wide' output):

[ root@test-curl:/ ]$ curl -g [fd00:101::2]:80 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0  68120      0 --:--:-- --:--:-- --:--:--  172k
<p>Pod: nginx-controller-kqd7c</p>
[ root@test-curl:/ ]$ curl -g [fd00:102::2]:80 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0  41710      0 --:--:-- --:--:-- --:--:-- 50428
<p>Pod: nginx-controller-gknzr</p>
[ root@test-curl:/ ]$

Curl the service's cluster-IP and service port (using prior 'kubectl get svc' output):

[ root@test-curl:/ ]$ curl -g [fd00:1234::3:b606]:8080 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0  54950      0 --:--:-- --:--:-- --:--:--  114k
<p>Pod: nginx-controller-kqd7c</p>
[ root@test-curl:/ ]$ curl -g [fd00:1234::3:b606]:8080 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0  87898      0 --:--:-- --:--:-- --:--:--  114k
<p>Pod: nginx-controller-zw565</p>
[ root@test-curl:/ ]$ curl -g [fd00:1234::3:b606]:8080 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0  46282      0 --:--:-- --:--:-- --:--:-- 50428
<p>Pod: nginx-controller-gknzr</p>
[ root@test-curl:/ ]$

Check that kube-dns can resolve the nginx-service:

[ root@test-curl:/ ]$ nslookup nginx-service
Server:    fd00:1234::10
Address 1: fd00:1234::10

Name:      nginx-service
Address 1: fd00:1234::3:b606
[ root@test-curl:/ ]$

Curl the service using the service name and service port:

[ root@test-curl:/ ]$ curl nginx-service:8080 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0   7423      0 --:--:-- --:--:-- --:--:--  344k
<p>Pod: nginx-controller-zw565</p>
[ root@test-curl:/ ]$ curl nginx-service:8080 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0  21695      0 --:--:-- --:--:-- --:--:-- 58833
<p>Pod: nginx-controller-sdx7w</p>
[ root@test-curl:/ ]$ curl nginx-service:8080 | grep controller
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   353  100   353    0     0   5684      0 --:--:-- --:--:-- --:--:-- 32090
<p>Pod: nginx-controller-gknzr</p>
[ root@test-curl:/ ]$

Exit the pod-curl pod

[ root@test-curl:/ ]$ exit
pod "test-curl" deleted
[root@kube-master nginx_v6]#