Normal domain name mapping maps the domain name to an IP address. For example example.com to the IP address 10.0.0.1. There are times though when we need to know what domain has a certain IP address and this is what a reverse zone provides. In normal DNS mapping you specify the domain name and IP address. Reverse DNS is IP address to domain name mapping - the opposite of forward (normal) DNS which maps domain names to IP addresses.

Every normal DNS record should have a reverse zone as well. It is mostly used by humans for such things as tracking where a web-site visitor came from, or where an e-mail message originated etc... Many e-mail servers on the Internet (including AOL's) are configured to reject incoming e-mails from any IP address which does not have reverse DNS.

In order to perform Reverse Mapping and to support normal recursive and Iterative (non-recursive) queries the DNS designers defined a special (reserved) Domain Name called IN-ADDR.ARPA. This domain allows for all supported Internet IPv4 addresses (and now IPv6).

Creating a New DNS Reverse Zone

1. Log into NetDirector and select the Bind DNS service from the Service Bar.
2. Once the Server Tree has automatically filtered itself to show only the DNS servers you have access to manage select the server or servers you wish to create the new zone on.
3. Select the Create New Master Zone option.
   
4. On the next page enter the information about the new zone.  There are several fields to be filled out to create the master zone.
• Zone Type - choose whether you are creating either a Forward or Reverse Zone. In this case choose the Reverse Zone option.
• Domain Name or Network - Enter the network of the zone you are creating. For example we entered "192.168.1"
• Records File - choose whether to have NetDirector automatcally create the appropiate zone file or define your own. In most cases you should leave this at "Automatic".
• Master Server - define the master nameserver for this domain. you can add additional nameservers for this domain later in the zone options for this domain. The Add NS record for master server? option will allow NetDirector to automatically create a nameserver record for this domain.
• Email address - enter the email address where someone responsible for this domain can be reached. 
• Timers - The timer options allow you to override the defualt timers with your own.
Typical values are:
Refresh time: 10800
Transfer retry time: 3600
Expiry time: 604800
Default time-to-live: 38400
5. Save your edits now by clicking the Create button. The changes will be processed and you now have the decision to either apply the change now or later. Or optionally you can continue to edit the DNS settings.
6. Once you are happy with the changes for DNS select either the Apply Now or Apply Changes Later. If making the change to several servers at once this may take a few seconds to complete.

Note: If you are going to schedule the changes to occur later you will need to select the calander icon to choose the date and time you want your change to happen.