# Validate IPv4/IPv6 dual-stack

Validate IPv4/IPv6 dual-stackThis document shares how to validate IPv4/IPv6 dual-stack enabled Kubernetes clusters.Before you beginProvider support for dual-stack networking (Cloud provider or otherwise must be able to provide Kubernetes nodes with routable IPv4/IPv6 network interfaces)A network plugin that supports dual-stack networking.Dual-stack enabled clusterYour Kubernetes server must be at or later than version v1.23.To check the version, enter kubectl version.Note:While you can validate with an earlier version, the feature is only GA and officially supported since v1.23.Validate addressingValidate node addressingEach dual-stack Node should have a single IPv4 block and a single IPv6 block allocated. Validate that IPv4/IPv6 Pod address ranges are configured by running the following command. Replace the sample node name with a valid dual-stack Node from your cluster. In this example, the Node's name is k8s-linuxpool1-34450317-0:kubectl get nodes k8s-linuxpool1-34450317-0 -o go-template --template='{{range .spec.podCIDRs}}{{printf "%s\n" .}}{{end}}' 10.244.1.0/24 2001:db8::/64 There should be one IPv4 block and one IPv6 block allocated.Validate that the node has an IPv4 and IPv6 interface detected. Replace node name with a valid node from the cluster. In this example the node name is k8s-linuxpool1-34450317-0:kubectl get nodes k8s-linuxpool1-34450317-0 -o go-template --template='{{range .status.addresses}}{{printf "%s: %s\n" .type .address}}{{end}}' Hostname: k8s-linuxpool1-34450317-0 InternalIP: 10.0.0.5 InternalIP: 2001:db8:10::5 Validate Pod addressingValidate that a Pod has an IPv4 and IPv6 address assigned. Replace the Pod name with a valid Pod in your cluster. In this example the Pod name is pod01:kubectl get pods pod01 -o go-template --template='{{range .status.podIPs}}{{printf "%s\n" .ip}}{{end}}' 10.244.1.4 2001:db8::4 You can also validate Pod IPs using the Downward API via the status.podIPs fieldPath. The following snippet demonstrates how you can expose the Pod IPs via an environment variable called MY_POD_IPS within a container. env: - name: MY_POD_IPS valueFrom: fieldRef: fieldPath: status.podIPs The following command prints the value of the MY_POD_IPS environment variable from within a container. The value is a comma separated list that corresponds to the Pod's IPv4 and IPv6 addresses.kubectl exec -it pod01 -- set | grep MY_POD_IPS MY_POD_IPS=10.244.1.4,2001:db8::4 The Pod's IP addresses will also be written to /etc/hosts within a container. The following command executes a cat on /etc/hosts on a dual stack Pod. From the output you can verify both the IPv4 and IPv6 IP address for the Pod.kubectl exec -it pod01 -- cat /etc/hosts # Kubernetes-managed hosts file. 127.0.0.1 localhost ::1 localhost ip6-localhost ip6-loopback fe00::0 ip6-localnet fe00::0 ip6-mcastprefix fe00::1 ip6-allnodes fe00::2 ip6-allrouters 10.244.1.4 pod01 2001:db8::4 pod01 Validate ServicesCreate the following Service that does not explicitly define .spec.ipFamilyPolicy. Kubernetes will assign a cluster IP for the Service from the first configured service-cluster-ip-range and set the .spec.ipFamilyPolicy to SingleStack.service/networking/dual-stack-default-svc.yaml apiVersion: v1 kind: Service metadata: name: my-service labels: app.kubernetes.io/name: MyApp spec: selector: app.kubernetes.io/name: MyApp ports: - protocol: TCP port: 80 Use kubectl to view the YAML for the Service.kubectl get svc my-service -o yaml The Service has .spec.ipFamilyPolicy set to SingleStack and .spec.clusterIP set to an IPv4 address from the first configured range set via --service-cluster-ip-range flag on kube-controller-manager.apiVersion: v1 kind: Service metadata: name: my-service namespace: default spec: clusterIP: 10.0.217.164 clusterIPs: - 10.0.217.164 ipFamilies: - IPv4 ipFamilyPolicy: SingleStack ports: - port: 80 protocol: TCP targetPort: 9376 selector: app.kubernetes.io/name: MyApp sessionAffinity: None type: ClusterIP status: loadBalancer: {} Create the following Service that explicitly defines IPv6 as the first array element in .spec.ipFamilies. Kubernetes will assign a cluster IP for the Service from the IPv6 range configured service-cluster-ip-range and set the .spec.ipFamilyPolicy to SingleStack.service/networking/dual-stack-ipfamilies-ipv6.yaml apiVersion: v1 kind: Service metadata: name: my-service labels: app.kubernetes.io/name: MyApp spec: ipFamilies: - IPv6 selector: app.kubernetes.io/name: MyApp ports: - protocol: TCP port: 80 Use kubectl to view the YAML for the Service.kubectl get svc my-service -o yaml The Service has .spec.ipFamilyPolicy set to SingleStack and .spec.clusterIP set to an IPv6 address from the IPv6 range set via --service-cluster-ip-range flag on kube-controller-manager.apiVersion: v1 kind: Service metadata: labels: app.kubernetes.io/name: MyApp name: my-service spec: clusterIP: 2001:db8:fd00::5118 clusterIPs: - 2001:db8:fd00::5118 ipFamilies: - IPv6 ipFamilyPolicy: SingleStack ports: - port: 80 protocol: TCP targetPort: 80 selector: app.kubernetes.io/name: MyApp sessionAffinity: None type: ClusterIP status: loadBalancer: {} Create the following Service that explicitly defines PreferDualStack in .spec.ipFamilyPolicy. Kubernetes will assign both IPv4 and IPv6 addresses (as this cluster has dual-stack enabled) and select the .spec.ClusterIP from the list of .spec.ClusterIPs based on the address family of the first element in the .spec.ipFamilies array.service/networking/dual-stack-preferred-svc.yaml apiVersion: v1 kind: Service metadata: name: my-service labels: app.kubernetes.io/name: MyApp spec: ipFamilyPolicy: PreferDualStack selector: app.kubernetes.io/name: MyApp ports: - protocol: TCP port: 80 Note:The kubectl get svc command will only show the primary IP in the CLUSTER-IP field.kubectl get svc -l app.kubernetes.io/name=MyApp NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE my-service ClusterIP 10.0.216.242 <none> 80/TCP 5s Validate that the Service gets cluster IPs from the IPv4 and IPv6 address blocks using kubectl describe. You may then validate access to the service via the IPs and ports.kubectl describe svc -l app.kubernetes.io/name=MyApp Name: my-service Namespace: default Labels: app.kubernetes.io/name=MyApp Annotations: <none> Selector: app.kubernetes.io/name=MyApp Type: ClusterIP IP Family Policy: PreferDualStack IP Families: IPv4,IPv6 IP: 10.0.216.242 IPs: 10.0.216.242,2001:db8:fd00::af55 Port: <unset> 80/TCP TargetPort: 9376/TCP Endpoints: <none> Session Affinity: None Events: <none> Create a dual-stack load balanced ServiceIf the cloud provider supports the provisioning of IPv6 enabled external load balancers, create the following Service with PreferDualStack in .spec.ipFamilyPolicy, IPv6 as the first element of the .spec.ipFamilies array and the type field set to LoadBalancer.service/networking/dual-stack-prefer-ipv6-lb-svc.yaml apiVersion: v1 kind: Service metadata: name: my-service labels: app.kubernetes.io/name: MyApp spec: ipFamilyPolicy: PreferDualStack ipFamilies: - IPv6 type: LoadBalancer selector: app.kubernetes.io/name: MyApp ports: - protocol: TCP port: 80 Check the Service:kubectl get svc -l app.kubernetes.io/name=MyApp Validate that the Service receives a CLUSTER-IP address from the IPv6 address block along with an EXTERNAL-IP. You may then validate access to the service via the IP and port.NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE my-service LoadBalancer 2001:db8:fd00::7ebc 2603:1030:805::5 80:30790/TCP 35s