Most networks of more than a handful of computers can benefit from the presence of a local DNS server. Such a server may serve both external clients who want to find the IP addresses associated with server names within your domain, and internal clients who want to find the IP addresses of both local and remote systems. In either case, you must configure a basic set of options, including general options, a specification of root name servers, and configuration for any zones for which you want the server to be authoritative . If you want the server to deliver the names of computers within your domain, you need to set this up within zone files for the server. These files allow you to link hostnames and IP addresses, and tie specific computers to particular functions within a zone, such as mail servers for a domain.