About the relation of IP and AS

[Lee Howard]

This probably isn't the best forum for this question.

Obviously there's some relation between the two, but like all relationships,
it changes often.  I'll use 63.10.0.0 as an example.  If you have an IP and 
want to know who owns it, use

	whois -h whois.arin.net 63.10.0.0

You'll find out that UUNET has been allocated that block.  You could then
do "whois -h whois.arin.net UUNET" to try to find our ASN, but you'll get
far more information than you want.  If you're on a Unix machine, you can
grep:

	whois -h whois.arin.net UUNET | grep AS

Unfortunatley, that doesn't give you the information you want, since 
the IP block above has a different name (Alternet.  it's historical).
So if you have an IP and want to know who is routing it, I suggest

	http://nitrous.digex.net
	or
	whois -h whois.ra.net 63.10.0.0

If you have an ASN and want to find out what IPs are being routed by it,
it's a little trickier.  One way is to buy transit from a large carrier,
receive a full routing table, and run the equivalent of Cisco's "show IP
BGP regexp 705".  A cheaper way is to log into a public route server and
use:

	route-views.oregon-ix.net>sh ip bgp regexp 705

Of course, there isn't a one-to-one relationship between IPs and ASNs
(they're not faithful to each other).  The same IP block is often routed
by multiple ASNs (in multihoming, for example).  Certainly most ASNs route
multiple IP blocks.  And of course, people and networks move around a lot,
which is why we use dynamic routing protocols.

Hope this helps.

Lee

On Wed, 11 Jul 2001, huiy wrote:

> Date: Wed, 11 Jul 2001 10:21:56 +0800 (CST)
> From: huiy <huiy at 263.net>
> To: policy at arin.net
> Subject: About the relation of IP and AS
> 
> Hi,
>   Is there some relations between IP address and AS numbers? I want to know an IP belong to which AS and the IPs an AS have. Where can I find it?
> Thanks a lot.
> 
> Challenge.
> 
> _____________________________________________
> IP¿¨¡¢ÉÏÍø¿¨ÈýÕÛÇÀ¹º  http://shopping.263.net/category08.htm
> »¨580ÔªÂòÊýÂëÏà»ú£¬ËÍ100ÔªIP¿¨ http://shopping.263.net/category21.htm
>