Update ocp-ipi-aws README
# OCP-IPI tool
-This set of scripts is designed to update openshift-installer provisioned AWS infrastructure
-to host submariner properly. Submariner needs at least one worker node with an external IP
-address, and marked with the submariner.io/gateway=true label.
+Submariner gateway nodes need to be able to accept traffic over UDP ports (4500 and 500 by default) when using IPsec. Submariner also uses
+UDP port 4800 to encapsulate traffic from the worker nodes to the gateway nodes. Additionally, the default OpenShift deployment does not
+allow assigning an elastic public IP to existing worker nodes, which may be necessary on one end of the IPsec connection.
-You can use the prep_for_subm.sh script on your openshift install directory with your AWS
-credentials correctly sourced.
+`prep_for_subm` is a script designed to update your OpenShift installer provisioned AWS infrastructure for Submariner deployments,
+handling the requirements specified above.
+
+You can use the `prep_for_subm.sh` script on your OpenShift install directory with your AWS credentials correctly sourced.
```bash
cd my-cluster-openshift-install-dir
@@ -14,19 +16,19 @@ chmod a+x ./prep_for_subm.sh
./prep_for_subm.sh
```
-You can override some of the defaults by using environment variables, like:
+Certain parameters, such as the IPsec UDP ports and AWS instance type for the gateway (default `m5n.large`), can be customized before
+running the script. For example:
```bash
export IPSEC_NATT_PORT=4501
export IPSEC_IKE_PORT=501
export GW_INSTANCE_TYPE=m4.xlarge
-./prep_for_subm.sh
```
## Prerequisites
You will need:
-* [Terraform](https://www.terraform.io/downloads.html)
+* [Terraform](https://releases.hashicorp.com/terraform/) version 0.12. Maximum compatible version is 0.12.12
* [AWS CLI tool](https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-install.html)
* [OC](https://cloud.redhat.com/openshift/install/aws/installer-provisioned)
