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I haven't cracked open the source code yet, but I was curious which whois service the traceroute program uses to look up ASNs for a given IP.

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up vote 8 down vote accepted

The copy running on my Linux box gets its answers from I was able to tell this by running tcpdump at the same time as running a traceroute.

The PTR records for that IP resolve to, and it happens that and point to the same IP address.

Further examination of the binary (with "strings") reveals that it's actually using the hostname. There's also a pair of (undocumented) environment variables ($RA_SERVER and $RA_SERVICE) which can change the host and port used for these queries.

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How did you determine that? – Noah Campbell Jun 11 '09 at 19:48
I ran tcpdump at the same time as a traceroute. – Alnitak Jun 11 '09 at 20:31

Having not looked at the source code, I would suspect either or or equivalent.

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