AS Number Lookup

Cojack · Posted: Tue May 06, 2003 11:23 pm Post subject: AS Number Lookup

I'm trying to find some kind of way to look up an AS number given an IP address. It would be ideal if I didn't have to call out to an external program, but at this point anything is better than nothing.

steveb · Advocate Joined: 18 Sep 2002 Posts: 4564

Cojack · Posted: Wed May 07, 2003 2:05 am Post subject:

Thanks for the reply. As it turns out, I can dig up the AS number for an address by querying WHOIS. I'd looked there before, but never found those values because I was just using the default query (didn't know you could alter the query). By turning on the "all databases" flag, you get a lot more information, which includes the AS number, among other things.

You learn something new every day. :roll:

steveb · Advocate Joined: 18 Sep 2002 Posts: 4564

cool

fragbert · Posted: Wed May 07, 2003 8:17 am Post subject:

If you're messing with BGP4, you might also be interested in using the free services on telnet://route-views.oregon-ix.net. It can be useful to see how the rest of the internet actually sees your AS.

The on-line WWW WHOIS on http://www.arin.net can also be helpful, as can the IRRd entries available on http://www.radb.net (which the ASN is also very likely registered in).

Michael

Cojack · Posted: Fri May 09, 2003 12:21 am Post subject:

Thanks for the replies. I've been working on a project to automatically correlate a hostname/ip with the geographic data provided by these guys:

http://www.caida.org/tools/utilities/netgeo/index.xml

They provide a CGI interface (and a set of java and perl API's) to do a lookup based on hostname, but that takes too long to repeatedly query. Thankfully, they also prodive a flat file with their data, but they index by AS number, hence my looking for a way to discover the AS numbers.

I'm not sure how much faster it'll be to do WHOIS -> ASN -> flat file query, since I've got to hit the network to find the ASN anyways. Something worth exploring, though. Ideally, I'd be able to call a function (or, slightly less ideally, call out to a program) which discovers the ASN directly, without having to download and parse a bunch of text. I noticed that the traceroute program at telnet://route-views.oregon-ix.net provides the AS number in realtime, which leads me to believe they're retrieving the number at a lower level.

I admit that I typically don't delve this low into routing issues, so my knowledge of these things is pretty rude.

fragbert · Posted: Sat May 10, 2003 8:12 am Post subject: