The vSphere IPI documentation explains how one should configure the cluster network operator object with IPSec enabled. This is how the it states that the install-config should look like: [1]

---
defaultNetwork:
  type: OVNKubernetes
  ovnKubernetesConfig:
    mtu: 1400
    genevePort: 6081
      ipsecConfig:
        mode: Full
---

This is incorrect and leads to an error in the installation due to an incorrect placement of the ipsecConfig inside the genvePort stanza. It should be placed outside under ovnKubernetesConfig, like:

---
defaultNetwork:
  type: OVNKubernetes
  ovnKubernetesConfig:
    mtu: 1400
    genevePort: 6081
    ipsecConfig:
      mode: Full
---

This causes error when installing:

FATAL failed to fetch Metadata: failed to fetch dependency of "Metadata": failed to fetch dependency of "Bootstrap Ignition Config": failed to generate asset "CVO Ignore": could not unmarshal "manifests/cluster-network-03-config.yml": error converting YAML to JSON: yaml: line 10: mapping values are not allowed in this context
make: *** [makefile:69: start-install] Error 1

[1] https://docs.openshift.com/container-platform/4.16/installing/installing_vsphere/ipi/installing-vsphere-installer-provisioned-network-customizations.html#nw-operator-cr-cno-object_installing-vsphere-installer-provisioned-network-customizations

    All the time, if the documentation is strictly followed.

    1. Write an install-config for vsphere IPI enabling IPSec according to the documentation
    2. Run the openshift-installer using the format described in the documentation
    3. See that the installer fails to correctly parse the install-config and generate the manifests

FATAL failed to fetch Metadata: failed to fetch dependency of "Metadata": failed to fetch dependency of "Bootstrap Ignition Config": failed to generate asset "CVO Ignore": could not unmarshal "manifests/cluster-network-03-config.yml": error converting YAML to JSON: yaml: line 10: mapping values are not allowed in this context make: *** [makefile:69: start-install] Error 1

The installation to proceed normally.