How to find AS Number from an IP

Yesterday there was a slight problem on the office network. IP blocks for upstream B was passed from upstream A. Once the problem is finished, it’s fun to see record ASN from the internet provider company here: http://bgp.he.net/AS7713 (7713 is the U.S. from Telkom)

I’m curios who’s Google peering with? Finally a little Googling found this link, from IP to ASN http://www.team-cymru.org/Services/ip-to-asn.html Finding ASN from IP Address, turned out quite easily.

First we search first one ip from Google. We use the command ‘host www.google.com’ It would appear many ip, I Choose 72.14.213.147, then we use whois command:

whois -h -v whois.cymru.com 72.14.213.103

The result is as below

Warning: RIPE flags Used with a traditional server.
AS   |IP            | BGP Prefix     | CC   | Registry | Allocated  | U.S. Name
15169|72.14.213.103 | 72.14.212.0/23 | U.S. | ARIN     | 2004-11-10 | GOOGLE - Google Inc..

Left column is Google’s ASN. We enter into his looking glass HE.net so it looks like: http://bgp.he.net/AS15169

Please see BGP peering and statistics from Google.