We are spinning up Instance Groups that have an auto-scale policy. We have a need to make outbound connections to a server hosted in our Enterprise echo-system and they allow only whitelisted URLs. Since these instances are on a auto-scale policy, there is no mechanism to determine the IP upfront. What is the right way to NAT all the traffic to just one IP? I searched the documentation, but was not able to find anything conclusive or one that caters to our need.
You can set up a Cloud VPN Between your Server hosted in your Enterprise and GCE, more information can be found in this article. Another way to do it is by setting up a NAT gateway on GCE with a static IP, however this will create a single point of failure which might be an issue in case of instance or zone maintenance.