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I would like to create "simple" tool for IP->AS mapping based on riswhois data.

i do not believe whois data have anything about as numbers

RISwhois is a whois interface to the RIS data, intended to provide a quick look at the collected BGP data. Format is compatible with routing registries so folk who have tools build on whois queries to IRR, can switch to RIS transparently. Useful for IP->AS mappings, but also for a first peek at BGP tables before diving deeper with other RIS tools (looking glass, prefix query etc.) See http://www.ripe.net/ripe/meetings/ripe-47/presentations/ripe47-eof-riswhois.... As for the question:

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Are there any good reasons to keep riswhois reporting default routes?

I think riswhois server should not do any filtering on the RIS data If someone feeds RIS a default route, it should pop up in the RRC looking glass, the RIS database and RISwhois. It's up to the application to use it or ignore it. If you don't want the currently present default route to appear in ever riswhois query, use the -M flag: whois -h riswhois.ripe.net -M <ip-number> will only return you the longest matching prefix. -- Rene