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Configuring ingress cluster traffic using a service external IP - Configuring ingress cluster traffic | Networking | OpenShift Container Platform 4.15
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Configuring ingress cluster traffic for a service external IP

You can use either a MetalLB implementation or an IP failover deployment to attach an ExternalIP resource to a service so that the service is available to traffic outside your OpenShift Container Platform cluster. Hosting an external IP address in this way is only applicable for a cluster installed on bare-metal hardware.

You must ensure that you correctly configure the external network infrastructure to route traffic to the service.

Prerequisites

Attaching an ExternalIP to a service

You can attach an ExternalIP resource to a service. If you configured your cluster to automatically attach the resource to a service, you might not need to manually attach an ExternalIP to the service.

The examples in the procedure use a scenario that manually attaches an ExternalIP resource to a service in a cluster with an IP failover configuration.

Procedure

  1. Confirm compatible IP address ranges for the ExternalIP resource by entering the following command in your CLI:

    $ oc get networks.config cluster -o jsonpath='{.spec.externalIP}{"\n"}'

    If autoAssignCIDRs is set and you did not specify a value for spec.externalIPs in the ExternalIP resource, OpenShift Container Platform automatically assigns ExternalIP to a new Service object.

  2. Choose one of the following options to attach an ExternalIP resource to the service:

    1. If you are creating a new service, specify a value in the spec.externalIPs field and array of one or more valid IP addresses in the allowedCIDRs parameter.

      Example of service YAML configuration file that supports an ExternalIP resource
      apiVersion: v1
kind: Service
metadata:
  name: svc-with-externalip
spec:
  externalIPs:
    policy:
      allowedCIDRs:
      - 192.168.123.0/28

    2. If you are attaching an ExternalIP to an existing service, enter the following command. Replace <name> with the service name. Replace <ip_address> with a valid ExternalIP address. You can provide multiple IP addresses separated by commas.

      $ oc patch svc <name> -p \
  '{
    "spec": {
      "externalIPs": [ "<ip_address>" ]
    }
  }'

      For example:

      $ oc patch svc mysql-55-rhel7 -p '{"spec":{"externalIPs":["192.174.120.10"]}}'
      Example output
      "mysql-55-rhel7" patched

  3. To confirm that an ExternalIP address is attached to the service, enter the following command. If you specified an ExternalIP for a new service, you must create the service first.

    $ oc get svc
    Example output
    NAME               CLUSTER-IP      EXTERNAL-IP     PORT(S)    AGE
mysql-55-rhel7     172.30.131.89   192.174.120.10  3306/TCP   13m

Additional resources