In a scenario where customers need to modify the subnet of ovn-kubernetes if that conflicts with their machine network or anything else then it doesn't work any more with adding an additional manifest there as per https://access.redhat.com/solutions/7084180

    4.19.6

    1. Replace the machine-network in install-config.yaml that falls in the 100.64.0.0/16 and run  openshift-install create manifests or cluster

The install-config is as,

..
..
networking:
  clusterNetwork:
  - cidr: 162.21.0.0/16
    hostPrefix: 23
  machineNetwork:
  - cidr: 100.64.40.0/24
  networkType: OVNKubernetes
  serviceNetwork:
  - 168.30.0.0/16

..
..    

# openshift-install create manifests 
ERROR failed to fetch Master Machines: failed to load asset "Install Config": failed to create install config: invalid "install-config.yaml" file: networking.machineNetwork[0]: Invalid value: "100.64.50.0/24": must not overlap with OVNKubernetes default internal subnet 100.64.0.0/16