Finding ASN from IP address

I want to create a mapping of IP addresses to ASN, for a specific like of IP addresses. Eg: 1.2.3.4 12.34.56.78 etc, gathered from my system logs. What is the best way of doing this? I thought about something along the lines of: install routing software (zebra?) pass software the IP's, get it to spit back a string from which I can grab the ASN Two problems being I don't know which software to install that can do that, or where to get a copy of the current routing table, so that I can feed that to the software. Suggestions appreciated. -- Avleen Vig Systems Administrator Personal: www.silverwraith.com EFnet: irc.mindspring.com