The CNAME Trick for Fractional In-addr.arpa Delegation


Assume the customer domain name is sampledomain.com, and that they have control over (are primary for) sampledomain.com. Also assume that the customer has been assigned 204.71.1.0/27 as their fractional class C network.

The fractional class C template would be:

[in-addr-cname.template.960313]
                            action: N
             network/prefix-length: 204.71.1.0/27
                domain name suffix: sampledomain.com
                        billing ID: 12345678
                       description: Set up records for 204.71.1.0/27
              primary contact name: Jane Smith
     primary contact email address: jsmith@sampledomain.com
      primary contact phone number: (123) 456-7890 x 101
            alternate contact name: John Doe
   alternate contact email address: jdoe@sampledomain.com
    alternate contact phone number: (123) 456-7890 x 102
 
  comments:  Thanks!
[EOF]


The records that will be added to the SKY Internet name server are:

0.1.71.204.in-addr.arpa.    IN      CNAME     204.71.1.0.sampledomain.com.
1.1.71.204.in-addr.arpa.    IN      CNAME     204.71.1.1.sampledomain.com.
[...]
31.1.71.204.in-addr.arpa.   IN      CNAME     204.71.1.31.sampledomain.com.


In the primary name server for sampledomain.com you would add PTR records, such as:

204.71.1.0.sampledomain.com.     IN      PTR     hostname.sampledomain.com.

You would substitute the actual host names of the systems instead of hostname.sampledomain.com above.


A sample query would then look like:

host -t ptr 1.1.71.204.in-addr.arpa
1.1.71.204.in-addr.arpa            CNAME    204.71.1.1.sampledomain.com
204.71.1.1.sampledomain.com        PTR      hostname1.sampledomain.com