Chapter 4 “Configuring and Managing the DNS Server Role”

Thursday, February 21, 2013

 The Domain Name System (DNS) role is the role that Microsoft Windows Server 2008 uses for name resolution.  When you send a request through your browser, for example, to a web site like www.yahoo.com, it’s DNSs responsibility to map the URL www.yahoo.com to its IP address so the request can be completed.  A DNS namespace is a tree structured list of host names in a hierarchical order starting with the root, which is unnamed and is represented by a period. Next is the top level domain, for example, .com, .net, or .edu, followed by a second level domain, which are registered to individuals, for example Yahoo (yahoo.com), Microsoft (Microsoft.com), or McHenry County College (mchenry.edu).  For administrative purposes, DNS can be organized into zones.  A DNS zone is a collection of name to IP address mappings in a contiguous portion of the DNS namespace which allows for sharing the workload across many other DNS servers.  A DNS zone can provide name to IP mappings for one or more domains.  If DNS is to provide for multiple domains they must be contiguous, or part of a parent child relationship.  There are three typical zone types that can be configured on a DNS server, the standard primary zone, the standard secondary zone, and the reverse lookup zone.  Windows Server 2003 and 2008 provide a fourth called a stub zone.  A standard primary zone hosts a read/write copy of the DNS zone in which resource records are created and managed.  Only one server can host a master copy of the zone, accept dynamic updates, and process zone changes.  A standard secondary zone is a read only copy of the primary zone and may be stored on one or more servers to provide fault tolerance and load balancing.  A reverse lookup zone can provide the hosts fully qualified domain name (FQDN) when a query contains “what is the host name at the IP address 69.147.76.15 it will return www.yahoo.com.  Finally, a stub zone is a copy of a zone that contains only the resources necessary to identify the authoritative DNS servers for that zone.  A stub zone does not have the same abilities as a secondary zone and should only be used for address redundancy and load sharing.