Assigning a static IP address for Knative on Kubernetes Engine

If you are running Knative on Google Kubernetes Engine and want to use a custom domain with your apps, you need to configure a static IP address to ensure that your custom domain mapping doesn’t break.

Knative configures an Istio Gateway CRD named knative-ingress-gateway under the knative-serving namespace to serve all incoming traffic within the Knative service mesh. The IP address to access the gateway is the external IP address of the “istio-ingressgateway” service under the istio-system namespace. Therefore, in order to set a static IP for the gateway you must to set the external IP address of the istio-ingressgateway service to a static IP.

If you have configured a custom ingress gateway, replace istio-ingressgateway with the name of your gateway service in the steps below.

Step 1: Reserve a static IP address

You can reserve a regional static IP address using the Google Cloud SDK or the Google Cloud Platform console.

Using the Google Cloud SDK:

  1. Enter the following command, replacing IP_NAME and REGION with appropriate values. For example, select the us-west1 region if you deployed your cluster to the us-west1-c zone:

    gcloud beta compute addresses create IP_NAME --region=REGION

    For example:

    gcloud beta compute addresses create knative-ip --region=us-west1
  2. Enter the following command to get the newly created static IP address:

    gcloud beta compute addresses list

    In the GCP console:

    1. Enter a name for your static address.
    2. For IP version, choose IPv4.
    3. For Type, choose Regional.
    4. From the Region drop-down, choose the region where your Knative cluster is running.

    For example, select the us-west1 region if you deployed your cluster to the us-west1-c zone.

    1. Leave the Attached To field set to None since we’ll attach the IP address through a config-map later.
    2. Copy the External Address of the static IP you created.

    Step 2: Update the external IP of istio-ingressgateway service

    Run following command to configure the external IP of the istio-ingressgateway service to the static IP that you reserved:

    INGRESSGATEWAY=istio-ingressgateway
    kubectl patch svc $INGRESSGATEWAY --namespace istio-system --patch '{"spec": { "loadBalancerIP": "<your-reserved-static-ip>" }}'

Step 3: Verify the static IP address of istio-ingressgateway service

Run the following command to ensure that the external IP of the ingressgateway service has been updated:

kubectl get svc $INGRESSGATEWAY --namespace istio-system

The output should show the assigned static IP address under the EXTERNAL-IP column:

NAME                     TYPE           CLUSTER-IP      EXTERNAL-IP     PORT(S)                                      AGE
xxxxxxx-ingressgateway   LoadBalancer   12.34.567.890   98.765.43.210   80:32380/TCP,443:32390/TCP,32400:32400/TCP   5m

Note: Updating the external IP address can take several minutes.

The external IP address should have a value now in the In use by column and should not be None anymore:

External IP address assigned