'nic whois warning

>24.in-addr.arpa has never been delegated.

What do you mean? Address space has been assigned by ARIN:

  There is no 24.in-addr.arpa zone. There are specific delegations
  underneith it.

  There are no nameservers for this zone, as demonstrated by your
  nslookup query.

  Also, ARIN records the registrations made by the IANA. This was
  the process as of four months ago, which was up to the point
  that Jon left us. Josh has told me that the IANA still approves
  every 24.in-addr.arpa delegation since this is the range for
  cable deployment and cable is not reserved for the ARIN service
  area. (yes cable does exist in Europe and Asia !)