Looking for good Bulk Reverse Lookup (Whois/Arin)

[CSO <cso-list01 () hypertec ca>]

Hello,

I want to do a bulk IP lookup on a bunch of IP's
And for the ones not resolved, I'd like to try ARIN WHOIS on them.

I whish to be able to export the results into a database.

The keyword here is BULK. 
What tools would you recommend to do that? (preferably freeware)

Thanks All,

Simon