I was trying to find a way to check whether an IP address is used by some host without actually probing it. DNS sounds like a good way to go, but I'v heard that domain "IN-ARPA.ADDR" is not well maintained and updated.

Is that true? If so, how un-dependable it could be?

Thanks a lot

Yixin Jin UCLA, Computer Science Dept.

the rumors of poorly maintained in-addr zones are just that. the data suggest that the forward tree was better maintained in, roughly 1993-1996/7. Since then there has been higher noise injection in the forward tree and the inverse tree has more accurate data. Rough numbers indicate that regardless of the database in question (whois, rwhois, DNS forward, DNS inverse, any of the iRR databases (ripe, RA, MCI, ANS and some of the newer ones like arin and apnic)) the data, as a whole, has about 40% inaccurate data. the reasons why are many but can be boiled down to at least two points: - centralized repositories "distance" people from the resources they have been delegated to manage. - there are few operational requirements for maintaining the accuracy of the data. YMMV. --bill