Windows DNS Servers

In a tradition DNS configuration, you have a set of at least 2 DNS servers who are responsible, or authoritative, for a zone. A zone is an administrative unit of DNS, and is represented by a set of DNS servers who are responsible for maintaining information relating to one or more domains or subdomains. One server in the setup acts as a primary name server, and this is the only server which carries a writable copy of the zone file. Periodically, the primary name server replicates its zone file to another server (or servers) designated as secondary name servers. These also carry a copy of the zone file, but the copy is read-only. The replication process is referred to as a zone transfer.

The primary reason for having 2 or more DNS servers be responsible for a zone is to ensure that should one fail, another will be available to answer queries relating to the domains stored in the zone file. This type of configuration continues to be supported in Windows 2000, and is referred to as being a ‘standard’ DNS setup. However, Windows 2000 also supports another type of DNS configuartion, which is new in Windows 2000. This configuration is called Active Directory Integrated DNS. In this setup, information about a DNS zone is stored in Active Directory, instead of being in a separate set of files. As such, DNS information is replicated automatically as part of Active Directory replication, and does not require a separate replication topology setup. This does not mean that every domain controller automatically becomes a DNS server. Instead, it means that every domain controller is capable of becoming a DNS server, if the DNS service is installed on that machine. Active Directory integrated DNS also has a number of other benefits, including the fact that every DNS server is writable, meaning that should a single one fail, DNS updates can still continue to be made. This is not true of a standard DNS setup, where updates cannot be made if the primary server goes offline.

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.