Configuring ingress cluster traffic using a service external IP - Configuring ingress cluster traffic | Networking

Using a service external IP to get traffic into the cluster
Creating a project and service
Exposing the service by creating a route

OpenShift Container Platform provides methods for communicating from outside the cluster with services running in the cluster. This method uses a service external IP.

Using a service external IP to get traffic into the cluster

One method to expose a service is to assign an external IP address directly to the service you want to make accessible from outside the cluster.

The external IP address that you use must be provisioned on your infrastructure platform and attached to a cluster node.

With an external IP on the service, OpenShift Container Platform sets up NAT rules to allow traffic arriving at any cluster node attached to that IP address to be sent to one of the internal pods. This is similar to the internal service IP addresses, but the external IP tells OpenShift Container Platform that this service should also be exposed externally at the given IP. The administrator must assign the IP address to a host (node) interface on one of the nodes in the cluster. Alternatively, the address can be used as a virtual IP (VIP).

These IPs are not managed by OpenShift Container Platform and administrators are responsible for ensuring that traffic arrives at a node with this IP.

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 username
```
Have an OpenShift Container Platform 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 do not exist, first create the project, then the service.

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

Prerequisites

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

Procedure

Create a new project for your service:

$ oc new-project <project_name>

For example:

$ oc new-project myproject

Use the oc new-app command to create a service. For example:

$ oc new-app \
    -e MYSQL_USER=admin \
    -e MYSQL_PASSWORD=redhat \
    -e MYSQL_DATABASE=mysqldb \
    registry.redhat.io/rhscl/mysql-80-rhel7

Run the following command to see that the new service is created:

$ oc get svc -n myproject
NAME             TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE
mysql-80-rhel7   ClusterIP   172.30.63.31   <none>        3306/TCP   4m55s

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.

Procedure

To expose the service:

Run the following command to expose the route:

$ oc expose service <service_name>

For example:

$ oc expose service mysql-80-rhel7
route "mysql-80-rhel7" exposed

Use a tool, such as cURL, to make sure you can reach the service using the cluster IP address for the service:
```
$ curl <pod_ip>:<port>
```
For example:
```
$ curl 172.30.131.89:3306
```
The examples in this section use a MySQL service, which requires a client application. If you get a string of characters with the Got packets out of order message, you are connected to the service.

If you have a MySQL client, log in with the standard CLI command:
```
$ mysql -h 172.30.131.89 -u admin -p
Enter password:
Welcome to the MariaDB monitor.  Commands end with ; or \g.

MySQL [(none)]>
```