In the install-config validation, we check that the hostPrefix is non-negative, not smaller than the clusterNetwork prefix. We also validate for IPv6 networks only that the host prefix must be equal to 64, so only IPv4 networks are discussed below.

The assisted-service applies additional validations:

• there must be at least 128 addresses per host; thus the prefix must be no more than 25.
• there must be room in the cluster network for all of the hosts in the cluster, or a minimum of 4 hosts for compact clusters.

These can be verified at ISO generation time, so we should fail immediately if they are not met instead of waiting for the user to boot the ISO.