An IPv4 block is a group of IPv4 addresses that is separated from a larger network by subnetting.
You cannot route addresses within a block until you have allotted them into a network. You can add and return blocks by IP range or CIDR notation. You can specify default DNS domains for IPv4 blocks with the defaultDomains property. To add a single default domain, specify the object ID for the required domain. To add multiple default domains, specify the object IDs for multiple domains as a comma-delimited list of domain object IDs.