OpenShift 4 IPI baremetal installation fails with "Error: could not contact Ironic API: timeout reached" while using a proxy and a provisioning network

Issue

While installing a new OpenShift 4 cluster with IPI baremetal method, having a proxy server and a provisioning network; Ironic access is timing out with "Error: could not contact Ironic API: timeout reached"

Upon reviewing the installation log evidence if found that Ironic API endpoint is not reachable:

time="2021-09-16T06:00:48-04:00" level=debug msg="module.masters.ironic_node_v1.openshift-master-host[0]: Still creating... [59m40s elapsed]"
time="2021-09-16T06:00:48-04:00" level=debug msg="module.masters.ironic_node_v1.openshift-master-host[1]: Still creating... [59m40s elapsed]"
time="2021-09-16T06:00:48-04:00" level=debug msg="module.masters.ironic_node_v1.openshift-master-host[2]: Still creating... [59m40s elapsed]"
time="2021-09-16T06:00:58-04:00" level=debug msg="module.masters.ironic_node_v1.openshift-master-host[2]: Still creating... [59m50s elapsed]"
time="2021-09-16T06:00:58-04:00" level=debug msg="module.masters.ironic_node_v1.openshift-master-host[0]: Still creating... [59m50s elapsed]"
time="2021-09-16T06:00:58-04:00" level=debug msg="module.masters.ironic_node_v1.openshift-master-host[1]: Still creating... [59m50s elapsed]"
time="2021-09-16T06:01:07-04:00" level=error
time="2021-09-16T06:01:07-04:00" level=error msg="Error: could not contact Ironic API: context deadline exceeded"
time="2021-09-16T06:01:07-04:00" level=error msg="Error: could not contact Ironic API: timeout reached"
time="2021-09-16T06:01:07-04:00" level=error
time="2021-09-16T06:01:07-04:00" level=fatal msg="failed to fetch Cluster: failed to generate asset \"Cluster\": failed to create cluster: failed to apply Terraform: error(BaremetalIronicAPITimeout) from Infrastructure Provider: Unable to the reach provisioning service. This failure can be caused by incorrect network/proxy settings, inability to download the machine operating system images, or other misconfiguration. Please check access to the bootstrap host, and for any failing services."