ASN to IP Mapping

Nick Hilliard nick at
Sat Mar 7 21:42:24 UTC 2015

On 07/03/2015 15:37, Andrew Iwamoto wrote:
> Is there a tool or method to determine IP blocks assigned to an
> organization by ASN?  I.e. if I have an organization's ASN number I want
> to know all blocks assigned to that ASN.

ip address blocks are not assigned to ASNs.  IP address blocks and ASNs are
assigned to organisations or people.

If IP address blocks are used on the public internet, there is no guarantee
that the ASN used to announce them is assigned to the same organisation
that was assigned those blocks.

Several people have made suggestions to use various lookup tools:

- IRR databases will often return garbage, and it is unwise to depend on
their output being accurate.

- live lookups up ASN announcements on the public internet will only tell
you who is currently announcing a particular prefix on a particular asn.
This will not give any information

- some RIR databases provide accurate allocation trails.  Probably the RIPE
NCC is most accurate / easy to use in this regard because of the way their
data is presented in their database.  This will only apply to allocations
they've made, though.

Anyway, it's not fully clear what you're asking.  If you need a more
specific answer, you will need to ask a more specific question.


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