With scarcity of IPv4 addresses, organizations are more desperate than ever to receive an allocation. If anything, there's more of a disincentive than ever before for ARIN to spend time on netblock sanitization. I do think that ARIN should inform the new netblock owner if it was previously owned or not. But if ARIN tried to start cleaning up a netblock before releasing it, there would be no end to it. How could they check against the probably hundreds of thousands private blocklist? Frank -----Original Message----- From: JC Dill [mailto:jcdill.lists@gmail.com] Sent: Wednesday, September 09, 2009 5:40 PM To: NANOG list Subject: Re: Repeated Blacklisting / IP reputation <snip> They can (and IMHO should) determine the state it is in before they reallocate it. What happens next is obviously unpredictable but in reality an IP that isn't being blocked today and isn't being used (by anyone) is highly unlikely to be widely blocked between today and the day ARIN releases it for allocation to a new entity. They can hold IPs that are not suitable for re-allocation, or at least make the status of the IPs known to the new entity before asking the entity to take on the IP block, and perhaps offering a fee discount for "tainted" addresses. (Some users may not care if the IPs are "tainted", if, for instance they plan to use the IPs for a DUL pool. I have a friend who gets $5 off his cell phone bill because he has a phone number that starts with 666 - a number that many people prefer to avoid but which works fine for his purposes and he's quite happy to get the discount. :-) <snip> ARIN shouldn't allocate previously allocated IPs until they know the IPs are not widely blocked. Or to *at the very least* ARIN should disclose what they know about the IP space before they make it someone else's problem, and give the requesting entity an option to request a new/clean/unused/unblocked IP block instead. <snip> jc