Chapter 2. Configuring a private cluster After you install an OpenShift Container Platform version 4.9 cluster, you can set some of its core components to be private. 2.1. About private clusters By default, OpenShift Container Platform is provisioned using publicly-accessible DNS and endpoints. You can set the DNS, Ingress Controller, and API server to private after you deploy your private cluster. Important If the cluster has any public subnets, load balancer services created by administrators might be publicly accessible. To ensure cluster security, verify that these services are explicitly annotated as private. DNS If you install OpenShift Container Platform on installer-provisioned infrastructure, the installation program creates records in a pre-existing public zone and, where possible, creates a private zone for the cluster's own DNS resolution. In both the public zone and the private zone, the installation program or cluster creates DNS entries for *.apps , for the Ingress object, and api , for the API server. The *.apps records in the public and private zone are identical, so when you delete the public zone, the private zone seamlessly provides all DNS resolution for the cluster. Ingress Controller Because the default Ingress object is created as public, the load balancer is internet-facing and in the public subnets. You can replace the default Ingress Controller with an internal one. API server By default, the installation program creates appropriate network load balancers for the API server to use for both internal and external traffic. On Amazon Web Services (AWS), separate public and private load balancers are created. The load balancers are identical except that an additional port is available on the internal one for use within the cluster. Although the installation program automatically creates or destroys the load balancer based on API server requirements, the cluster does not manage or maintain them. As long as you preserve the cluster's access to the API server, you can manually modify or move the load balancers. For the public load balancer, port 6443 is open and the health check is configured for HTTPS against the /readyz path. On Google Cloud Platform, a single load balancer is created to manage both internal and external API traffic, so you do not need to modify the load balancer. On Microsoft Azure, both public and private load balancers are created. However, because of limitations in current implementation, you just retain both load balancers in a private cluster. 2.2. Setting DNS to private After you deploy a cluster, you can modify its DNS to use only a private zone. Procedure Review the DNS custom resource for your cluster: USD oc get dnses.config.openshift.io/cluster -o yaml Example output apiVersion: config.openshift.io/v1 kind: DNS metadata: creationTimestamp: "2019-10-25T18:27:09Z" generation: 2 name: cluster resourceVersion: "37966" selfLink: /apis/config.openshift.io/v1/dnses/cluster uid: 0e714746-f755-11f9-9cb1-02ff55d8f976 spec: baseDomain: <base_domain> privateZone: tags: Name: <infrastructure_id>-int kubernetes.io/cluster/<infrastructure_id>: owned publicZone: id: Z2XXXXXXXXXXA4 status: {} Note that the spec section contains both a private and a public zone. Patch the DNS custom resource to remove the public zone: USD oc patch dnses.config.openshift.io/cluster --type=merge --patch='{"spec": {"publicZone": null}}' dns.config.openshift.io/cluster patched Because the Ingress Controller consults the DNS definition when it creates Ingress objects, when you create or modify Ingress objects, only private records are created. Important DNS records for the existing Ingress objects are not modified when you remove the public zone. Optional: Review the DNS custom resource for your cluster and confirm that the public zone was removed: USD oc get dnses.config.openshift.io/cluster -o yaml Example output apiVersion: config.openshift.io/v1 kind: DNS metadata: creationTimestamp: "2019-10-25T18:27:09Z" generation: 2 name: cluster resourceVersion: "37966" selfLink: /apis/config.openshift.io/v1/dnses/cluster uid: 0e714746-f755-11f9-9cb1-02ff55d8f976 spec: baseDomain: <base_domain> privateZone: tags: Name: <infrastructure_id>-int kubernetes.io/cluster/<infrastructure_id>-wfpg4: owned status: {} 2.3. Setting the Ingress Controller to private After you deploy a cluster, you can modify its Ingress Controller to use only a private zone. Procedure Modify the default Ingress Controller to use only an internal endpoint: USD oc replace --force --wait --filename - <<EOF apiVersion: operator.openshift.io/v1 kind: IngressController metadata: namespace: openshift-ingress-operator name: default spec: endpointPublishingStrategy: type: LoadBalancerService loadBalancer: scope: Internal EOF Example output ingresscontroller.operator.openshift.io "default" deleted ingresscontroller.operator.openshift.io/default replaced The public DNS entry is removed, and the private zone entry is updated. 2.4. Restricting the API server to private After you deploy a cluster to Amazon Web Services (AWS) or Microsoft Azure, you can reconfigure the API server to use only the private zone. Prerequisites Install the OpenShift CLI ( oc ). Have access to the web console as a user with admin privileges. Procedure In the web portal or console for AWS or Azure, take the following actions: Locate and delete appropriate load balancer component. For AWS, delete the external load balancer. The API DNS entry in the private zone already points to the internal load balancer, which uses an identical configuration, so you do not need to modify the internal load balancer. For Azure, delete the api-internal rule for the load balancer. Delete the api.USDclustername.USDyourdomain DNS entry in the public zone. Remove the external load balancers: Important You can run the following steps only for an installer-provisioned infrastructure (IPI) cluster. For a user-provisioned infrastructure (UPI) cluster, you must manually remove or disable the external load balancers. From your terminal, list the cluster machines: USD oc get machine -n openshift-machine-api Example output NAME STATE TYPE REGION ZONE AGE lk4pj-master-0 running m4.xlarge us-east-1 us-east-1a 17m lk4pj-master-1 running m4.xlarge us-east-1 us-east-1b 17m lk4pj-master-2 running m4.xlarge us-east-1 us-east-1a 17m lk4pj-worker-us-east-1a-5fzfj running m4.xlarge us-east-1 us-east-1a 15m lk4pj-worker-us-east-1a-vbghs running m4.xlarge us-east-1 us-east-1a 15m lk4pj-worker-us-east-1b-zgpzg running m4.xlarge us-east-1 us-east-1b 15m You modify the control plane machines, which contain master in the name, in the following step. Remove the external load balancer from each control plane machine. Edit a control plane Machine object to remove the reference to the external load balancer: USD oc edit machines -n openshift-machine-api <master_name> 1 1 Specify the name of the control plane, or master, Machine object to modify. Remove the lines that describe the external load balancer, which are marked in the following example, and save and exit the object specification: ... spec: providerSpec: value: ... loadBalancers: - name: lk4pj-ext 1 type: network 2 - name: lk4pj-int type: network 1 2 Delete this line. Repeat this process for each of the machines that contains master in the name.

Commands:
oc get dnses.config.openshift.io/cluster -o yaml
apiVersion: config.openshift.io/v1 kind: DNS metadata: creationTimestamp: "2019-10-25T18:27:09Z" generation: 2 name: cluster resourceVersion: "37966" selfLink: /apis/config.openshift.io/v1/dnses/cluster uid: 0e714746-f755-11f9-9cb1-02ff55d8f976 spec: baseDomain: <base_domain> privateZone: tags: Name: <infrastructure_id>-int kubernetes.io/cluster/<infrastructure_id>: owned publicZone: id: Z2XXXXXXXXXXA4 status: {}
oc patch dnses.config.openshift.io/cluster --type=merge --patch='{"spec": {"publicZone": null}}' dns.config.openshift.io/cluster patched
oc get dnses.config.openshift.io/cluster -o yaml
apiVersion: config.openshift.io/v1 kind: DNS metadata: creationTimestamp: "2019-10-25T18:27:09Z" generation: 2 name: cluster resourceVersion: "37966" selfLink: /apis/config.openshift.io/v1/dnses/cluster uid: 0e714746-f755-11f9-9cb1-02ff55d8f976 spec: baseDomain: <base_domain> privateZone: tags: Name: <infrastructure_id>-int kubernetes.io/cluster/<infrastructure_id>-wfpg4: owned status: {}
oc replace --force --wait --filename - <<EOF apiVersion: operator.openshift.io/v1 kind: IngressController metadata: namespace: openshift-ingress-operator name: default spec: endpointPublishingStrategy: type: LoadBalancerService loadBalancer: scope: Internal EOF
ingresscontroller.operator.openshift.io "default" deleted ingresscontroller.operator.openshift.io/default replaced
oc get machine -n openshift-machine-api
NAME STATE TYPE REGION ZONE AGE lk4pj-master-0 running m4.xlarge us-east-1 us-east-1a 17m lk4pj-master-1 running m4.xlarge us-east-1 us-east-1b 17m lk4pj-master-2 running m4.xlarge us-east-1 us-east-1a 17m lk4pj-worker-us-east-1a-5fzfj running m4.xlarge us-east-1 us-east-1a 15m lk4pj-worker-us-east-1a-vbghs running m4.xlarge us-east-1 us-east-1a 15m lk4pj-worker-us-east-1b-zgpzg running m4.xlarge us-east-1 us-east-1b 15m
oc edit machines -n openshift-machine-api <master_name> 1
spec: providerSpec: value: loadBalancers: - name: lk4pj-ext 1 type: network 2 - name: lk4pj-int type: network