Setting Up Subdomains--Same Zone

Data files for multi-domain zones must include records for all machines and servers in each domain covered by the zone.

Setting up a multi-domain zone is the same as setting up a zone with a single domain, except that fully qualified domain names are used in the hosts file to identify machines in remote domains. In other words, in the hosts file, when you identify a machine in the server's local domain, you need to use only the machine's name. But when you identify a machine in some other domain, you must identify the machine with a fully qualified domain name in the format: machine.domain.

Server and machine names in hosts.rev and named.local files also need to be fully qualified with domain names. But that is true regardless of whether or not the zone has more than one domain.