For decades the only common method for accessing data in all the Regional Internet Registries (RIRs) has been Whois. Unfortunately, as a protocol, Whois does not specify any queries or responses making true interoperability between RIRs very difficult. This situation is even worse for domain registries.
ARIN’s RDAP services are composed of an RDAP version of its WHOIS system, essentially returning ARIN registration data in RDAP format, and an RDAP bootstrap service.
ARIN’s bootstrap service is located at https://rdap.arin.net/bootstrap. A query for IP address 220.127.116.11 would look like this: https://rdap.arin.net/bootstrap/ip/18.104.22.168. That query results in a redirect to APNIC, whereas http://rdap.arin.net/bootstrap/ip/22.214.171.124 results in a redirect to ARIN’s RDAP registry service (located at https://rdap.arin.net/registry). Incidentally, the code for ARIN’s RDAP bootstrap service is open source and available on GitHub.
ARIN has also made available an RDAP command-line client called NicInfo. This is an open source, Ruby program, and most recent versions of Linux and Mac OS can be simply installed with ‘gem install nicinfo’. More information on NicInfo can be found on its GitHub pages.