IPv4 Reverse DNS data

Reverse DNS (RDNS) data lists the domain names for all public IPv4 addresses.

The ANT project first collected RDNS data in 2013, and we are currently in the process of collecting such data. We expect to provide periodic snapshots of the IPv4 RDNS tree.

Some datasets:

Dataset Format

Each file is in Fsdb format, a tab-separated text format with # comments. The schema is:

 #fsdb -F t block hexip ip answer authority
 01000400        01000400 ip1.ip0.ip4.ip0.reverse.bigredgroup.net.au.     -
 01000400        01000401 loop0.brg_mel01_7206.bigredgroup.net.au.        -
  • block is each /24, in hex format, with trailing zeros (this field is redundant with hexip, but useful because many studies are on blocks)
  • hexip is the full IPv4 address in hex format
  • ip is the full IPv4 address in format (this field is redundant)
  • answer is the reverse-DNS name for the IP address, or - if none was returned.
  • authority is the SOA record in the authority section, if there is no answer. (If there is an answer, it is -).
  • rrsig is an additional column we expect to collect that is the DNSSEC signature, if any

Each file is sorted by hexip.

Getting this data

See our datasets request page for details about how to get these datasets.


Our current RDNS crawling software is available.