Configuring ingress cluster traffic using a NodePort - Configuring ingress cluster traffic | Networking

Using a NodePort to get traffic into the cluster
Prerequisites
Creating a project and service
Exposing the service by creating a route
Additional resources

OKD provides methods for communicating from outside the cluster with services running in the cluster. This method uses a NodePort.

Using a NodePort to get traffic into the cluster

Use a NodePort-type Service resource to expose a service on a specific port on all nodes in the cluster. The port is specified in the Service resource’s .spec.ports[*].nodePort field.

Using a node port requires additional port resources.

A NodePort exposes the service on a static port on the node’s IP address. NodePorts are in the 30000 to 32767 range by default, which means a NodePort is unlikely to match a service’s intended port. For example, port 8080 may be exposed as port 31020 on the node.

The administrator must ensure the external IP addresses are routed to the nodes.

NodePorts and external IPs are independent and both can be used concurrently.

The procedures in this section require prerequisites performed by the cluster administrator.

Prerequisites

Before starting the following procedures, the administrator must:

Set up the external port to the cluster networking environment so that requests can reach the cluster.
Make sure there is at least one user with cluster admin role. To add this role to a user, run the following command:
```
$ oc adm policy add-cluster-role-to-user cluster-admin <user_name>
```
Have an OKD cluster with at least one master and at least one node and a system outside the cluster that has network access to the cluster. This procedure assumes that the external system is on the same subnet as the cluster. The additional networking required for external systems on a different subnet is out-of-scope for this topic.

Creating a project and service

If the project and service that you want to expose does not exist, create the project and then create the service.

If the project and service already exists, skip to the procedure on exposing the service to create a route.

Prerequisites

Install the OpenShift CLI (oc) and log in as a cluster administrator.

Procedure

Create a new project for your service by running the oc new-project command:
```
$ oc new-project <project_name>
```

Use the oc new-app command to create your service:

$ oc new-app nodejs:12~https://github.com/sclorg/nodejs-ex.git

To verify that the service was created, run the following command:

$ oc get svc -n <project_name>

Example output

NAME        TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
nodejs-ex   ClusterIP   172.30.197.157   <none>        8080/TCP   70s

By default, the new service does not have an external IP address.

Exposing the service by creating a route

You can expose the service as a route by using the oc expose command.

Prerequisites

You logged into OKD.

Procedure

Log in to the project where the service you want to expose is located:
```
$ oc project <project_name>
```
To expose a node port for the application, modify the custom resource definition (CRD) of a service by entering the following command:
```
$ oc edit svc <service_name>
```
Example output
```
spec:
  ports:
  - name: 8443-tcp
    nodePort: 30327 (1)
    port: 8443
    protocol: TCP
    targetPort: 8443
  sessionAffinity: None
  type: NodePort (2)
```
1 Optional: Specify the node port range for the application. By default, OKD selects an available port in the 30000-32767 range.

2 Define the service type.

Optional: To confirm the service is available with a node port exposed, enter the following command:

$ oc get svc -n myproject

Example output

NAME                TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
nodejs-ex           ClusterIP   172.30.217.127   <none>        3306/TCP         9m44s
nodejs-ex-ingress   NodePort    172.30.107.72    <none>        3306:31345/TCP   39s

Optional: To remove the service created automatically by the oc new-app command, enter the following command:
```
$ oc delete svc nodejs-ex
```

Verification

To check that the service node port is updated with a port in the 30000-32767 range, enter the following command:
```
$ oc get svc
```
In the following example output, the updated port is 30327:
Example output
```
NAME    TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
httpd   NodePort   172.xx.xx.xx    <none>        8443:30327/TCP   109s
```

1	Optional: Specify the node port range for the application. By default, OKD selects an available port in the `30000-32767` range.
2	Define the service type.

Configuring ingress cluster traffic by using a NodePort

Using a NodePort to get traffic into the cluster

Prerequisites

Creating a project and service

Exposing the service by creating a route

Additional resources