The Internet address space allocation is managed by a number of different organizations. These registries provide IP allocation information through their whois servers.

To find the allocation information for a specific IP address, query it first using the ARIN whois server. If the IP address is allocated through any of the other registries this information will be reported by ARIN. More lookups will be required to locate the actual data.

When large IP blocks are allocated to a large organization, there may be other whois servers internal to the organization. This means even more lookups.

WhoisView is a free Windows software tool that makes looking up IP addresses very simple. It will retrieve the ownership information by digging through various whois servers automatically. It will find information all other similar tools are unable to or don't bother to locate.

Organizations responsible for IP allocations

American Region

The Internet numbering resources for North America is managed by American Registry for Internet Numbers (ARIN).

Web Site: www.arin.net
Whois Server: whois.arin.net

Asia/Oceania Region

Asia Pacific Network Information Centre (APNIC) serves the Asia Pacific region, comprising the countries in Asia and Australia.

Web Site: www.apnic.net
Whois Server: whois.apnic.net

Europe & Middle East

The RIPE Network Coordination Centre (RIPE NCC) manages the IP allocation in Europe, The Middle East, The North of Africa and parts of Asia.

Web Site: www.ripe.net
Whois Server: whois.ripe.net

Latin American & Caribbean Region

The Latin American and Caribbean IP address Regional Registry (LACNIC), is the emerging organization that will administer the Latin American and Caribbean Region IP address space.

Web Site: www.lacnic.org
Whois Server: whois.lacnic.net

African Region

The African Network Information Center (AfriNIC), is the emerging organization that will administer IP allocation for Africa.

Web Site: www.afrinic.org