Origin ASN seen vs Origin ASN in Whois Records Report?

Stephen Sprunk stephen at sprunk.org
Mon Nov 24 02:17:32 UTC 2008

Joe Abley wrote:
> On 19 Nov 2008, at 19:16, Heather Schiller wrote:
>> ARIN makes available a list of prefixes with OriginAS.  I don't know 
>> if other RIR's do.
> How is that list generated?
> I'm not aware of any tight coupling between address assignment and AS 
> assignment that binds anybody to advertise particular routes with 
> particular origins, at least at the time that either is 
> assigned/allocated by an RIR/LIR.

Presumably it's from the "Origin AS" field in WHOIS:


Template: ARIN-NET-MOD-4.1
**  As of February 2007
**  Detailed instructions are located below the template.

01. Registration Action (M or R): 
02. IP Address and Prefix or Range:
03. Network Name:
04. Origin AS:


04. List all AS numbers from which the network may originate.
    You can list as many AS numbers as necessary. You must 
    separate multiple AS numbers with a comma. You may not list 
    AS number ranges; only list individual AS numbers.

Interesting is how accurate the field actually is.  Slide 6 at:


says that 91% of the routes they checked had a correct Origin AS in 
WHOIS, compared to 64% in the ARIN IRR database.

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