title: Firewall issue - egress from GKE to Cloud Function HTTP Trigger
body: <p>I am developing a solution where a Java application hosted on GKE wants to make an <strong>outbound</strong> HTTP call to a cloud function which is deployed under a <strong>different</strong> GCP project, where the GKE operates on a shared network of which possesses firewall rules for the CIDR ranges in that shared network.</p>
  <p><strong>For example</strong> - GKE cluster &amp; Application deployed under GCP Project <strong>A</strong>, wishes to invoke a Serverless GCP Function deployed to project <strong>B</strong>.</p>
  <p>There are a number of firewall rules configured on the shared network of which the GKE is operating upon, causing my HTTP call to time out, as the HTTP trigger URL is not mapped to an allowed CIDR range (in that shared network).</p>
  <p><strong>What have I tried?</strong></p>
  <p>I have lightly investigated one or two solutions which make use of Cloud NAT &amp; Router to proxy the HTTP call to the Cloud Function trigger endpoint, but I am wondering if there are any other, simpler suggestions? The address range for cloud functions is massive so allowing that range is out of the question.</p>
  <p>I was thinking about maybe deploying the cloud function into the same VPC &amp; applying ingress restrictions to it, would that allow the HTTP trigger to exist in the allowed IP range?</p>
  <p>Thanks in advance</p>