zones explained

Kevin Darcy kcd at
Thu Mar 3 00:43:09 UTC 2005

tom wrote:

>i'm trying to setup a DNS server using named (BIND 9.2.3rc2).
>could anyone point me to some info that would explain the concepts of 
>'zones' and how they need to be handled if you don't actually have a 
>domain to manage (eg. soho network)?
Zones are like tables in a big database, that can be defined at any 
juncture in the namespace hierarchy. The contents of a zone consist of 
all records in a particular *domain* (e.g. and everything 
beneath it, e.g., minus the contents of any zones 
that reside beneath (e.g. if is a zone, then the zone would not include any of the records contained in it, 
ditto for any other subdomains which are delegated as zones unto 

If you have no "domain to manage", i.e. if your nameserver is not 
serving any zone content, then really the only zone you absolutely must 
care about is the "root" zone, which is at the top of the namespace 
hierarchy. At startup time, your BIND instance will attempt to determine 
the servers of the root zone, and once it gets that info, as queries 
come in to be resolved, it'll work its way down from there to various 
parts of the namespace hierarchy to resolve them. The ways that BIND 
gets this initial root-zone information is either a) by being 
authoritative (master or slave) for the root zone (this is unlikely to 
be an option for an Internet-resolving nameserver, but is doable in an 
internal-root architecture), b) by forwarding to some other 
nameserver(s), or c) by having a "." (i.e. root) zone of type "hint" 
configured into it, where the "hints" zone file contains only the names 
and addresses of root servers (BIND doesn't take the contents of the 
"hints" file as gospel though: it generates "priming" queries to the 
servers mentioned in the "hints" file to get the most current root-zone 
information, and will generate a warning message if the contents of your 
"hints" file does not match reality).

All of this is covered in the _DNS_and_BIND_ book from O'Reilly, which 
is considered the "bible" on the subject...

                                 - Kevin

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