Tech Tips / Windows NT / Networking



Understanding DNS, part 1

Since the advent of the Internet most network administrators have had to become familiar with DNS, which is a fairly complex subject. In addition to its Web-based applications, DNS is also used for internal name resolution. The DNS Manager tool in Windows NT lets you manage DNS servers effectively, but it's helpful if you know what's actually happening and what all those zones are about.

A zone file contains resource records for computers within the zone for which the DNS server has authority. Windows NT DNS servers may be configured as Primary, Secondary, or Caching Name Servers. So what's the difference?

A Primary server is the first DNS server created, and it gets its data from local DNS database files, created when you install DNS. A Secondary server gets its information from the Primary server in a process called Zone Transfer, when the Primary server sends a copy to it. The purpose of a Secondary server is to provide fault tolerance, redundancy, and some load balancing. Generally, it's best to install Primary and Secondary servers on different subnets so that if one subnet goes down, name resolution can still occur. A Caching server simply remembers information about queries that occur but is not the authority (or the "go-to guy") for any zone.

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