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A frequent question that faces network administrators or application developers consists in identifying who is using a specific public IP address. This information can be utilised for instance to perform user localisation and enable location-based services or user access control. In this context, a main technical challenge is to associate the IP address with its corresponding Autonomous System (AS).
Limitations of the whois information
A typical method to identify the AS that announces a specific IP address is to use the whois protocol. A whois command is available on main OSes and enables to query the databases of regional registries such as ARIN, RIPE, LACNINC, … A very interesting [article][1] provides tips for using the whois command. Here is a simple example that queries the whois.ripe.net server database in order to find the origin AS of the 148.60.0.0/16.
<pre class=“brush:shell”>$ whois -h whois.ripe.net 148.60.0.0/16 | grep origin origin: AS2200 </pre>
One way to do this is by querying the whois server of a routing registry such as RADB or RIPE, and looking for the origin attribute of a route object. However, not all networks properly register their route objects, so the information might not be available or may be outdated. Another method is by looking at the actual BGP route table for the origin AS of a prefix. You could do this on your own BGP speaking routers or on a public route server with the “show ip bgp” command (or equivalent), or by using one of the public looking glasses on the web. However, this method is cumbersome, especially if you want to quickly look up something or if you have a large number of addresses that you want to analyze with a script. Team Cymru (known for its bogon prefix list) has made a whois server available which provides the announcing AS number and name for any given IP address. The information in its database is based on 17 BGP feeds and is updated twice per hour. If your operating system has a command-line whois client, simply type “whois -h whois.cymru.com” followed on the same line by the IP address you would like to look up. In addition to simple lookups as described above, the server also supports comments and multiple addresses per query. Both of these features are especially useful if you have a script to analyze a large number of IP addresses from a script. For more information about these features, see the server's web page or type “whois -h whois.cymru.com help”. Update: A similar service was announced by the RIPE RIS project. Their whois server can be queried using “whois -h riswhois.ripe.net”, and returns results in RPSL like format (as used by the RIPE whois database itself). The data is gathered from route collector boxes in various locations. For more information about this service, see this web page.
Using BGP information
<pre class=“brush:shell”>simurgh$ whois -h riswhois.ripe.net 217.70.180.132 % This is RIPE NCC's Routing Information Service % whois gateway to collected BGP Routing Tables % IPv4 or IPv6 address to origin prefix match % % For more information visit http://www.ripe.net/ris/riswhois.html
route: 192.0.0.0/3 origin: AS3303 descr: SWISSCOM Swisscom (Switzerland) Ltd lastupd-frst: 2013-11-09 23:48Z 192.65.185.140@rrc04 lastupd-last: 2013-11-09 23:48Z 192.65.185.243@rrc04 seen-at: rrc04 num-rispeers: 2 source: RISWHOIS
route: 217.0.0.0/8 origin: AS3303 descr: SWISSCOM Swisscom (Switzerland) Ltd lastupd-frst: 2013-09-24 09:23Z 217.29.66.120@rrc10 lastupd-last: 2013-11-09 23:48Z 192.65.185.243@rrc04 seen-at: rrc04,rrc10 num-rispeers: 3 source: RISWHOIS
route: 217.70.176.0/20 origin: AS29169 descr: GANDI-AS Gandi SAS lastupd-frst: 2013-07-04 02:06Z 198.32.176.24@rrc14 lastupd-last: 2013-11-11 15:53Z 195.69.146.99@rrc03 seen-at: rrc00,rrc01,rrc03,rrc04,rrc05,rrc06,rrc07,rrc10,rrc11,rrc12,rrc13,rrc14,rrc15 num-rispeers: 114 source: RISWHOIS </pre>
## A Do-It-Yourself BGP query service
[1]: http://answers.oreilly.com/topic/408-how-to-use-and-understand-whois-in-its-many-forms/