Knative uses a shared Gateway to serve all incoming traffic within Knative service mesh, which is the "knative-shared-gateway" Gateway under "knative-serving" namespace. The IP address to access the gateway is the external IP address of the "knative-ingressgateway" service under the "istio-system" namespace. So in order to set static IP for the Knative shared gateway, you just need to set the external IP address of the "knative-ingressgateway" service to the static IP you need.
If you are running Knative cluster on GKE, you can follow the instructions to reserve a REGIONAL IP address. The region of the IP address should be the region your Knative cluster is running in (e.g. us-east1, us-central1, etc.).
TODO: add documentation on reserving static IP in other cloud platforms.
Follow the instructions to deploy Istio and Knative Serving into your cluster.
Once you reach this point, you can start to set up static IP for Knative gateway.
Run following command to reset the external IP for the "knative-ingressgateway" service to the static IP you reserved.
kubectl patch svc knative-ingressgateway -n istio-system --patch '{"spec": { "loadBalancerIP": "<your-reserved-static-ip>" }}'You can check the external IP of the "knative-ingressgateway" service with:
kubectl get svc knative-ingressgateway -n istio-systemThe result should be something like
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
knative-ingressgateway LoadBalancer 10.50.250.120 35.210.48.100 80:32380/TCP,443:32390/TCP,32400:32400/TCP 5h
The external IP will be eventually set to the static IP. This process could take several minutes.