Finding ASN from IP address

Fri Oct 10 08:51:27 UTC 2003

Avleen,

> I want to create a mapping of IP addresses to ASN, for a specific like
> of IP addresses. Eg:
>   1.2.3.4
>   12.34.56.78
>
> etc, gathered from my system logs.
>
> What is the best way of doing this?
>
> I thought about something along the lines of:
>   install routing software (zebra?)
>   pass software the IP's, get it to spit back a string from which I can
>     grab the ASN

Starting from the routing table is indeed the best approach.  We recently
studied this problem and found that an approach based on whois queries to
an IRR only returns the correct result in ~80% of the cases, whereas using
routing tables returns the correct result in ~99% of the cases. See:

http://www.ripe.net/ripe/meetings/ripe-46/presentations/ripe46-tt-as-traceroutes.pdf

for more details. We're expanding the software used for this study into a
public service right now and hope to announce this to the public shortly.

Henk

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That problem that we weren't having yesterday, is it better? (Big ISP NOC)