How to Find IP Address Ranges Owned by a Company

If you have a firewall, you may want to whitelist and/or blacklist some IPs depending in the origin. Usually it’s easy to find the owner of an IP address, but how can you find the IP address(es) registered by one specific company ?

Let’s say you want to whitelist Technorati bot.

A simple way is to go to http://bgp.he.net/ and enter the company name (e.g. technorati). It will return the IP list as follows:

ResultDescription
AS16936Technorati, Inc.
208.66.66.0/23Technorati, Inc.
208.66.65.0/24Technorati, Inc.
208.66.64.0/24Technorati, Inc.
208.66.64.0/22Technorati, Inc.

I understand the AS entries correspond to the Internet provider, and the IP address ranges can be added to your firewall (I use CloudFlare service)  whitelist.

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