Repeated Blacklisting / IP reputation

Frank Bulk frnkblk at
Sun Sep 13 04:08:16 UTC 2009

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?

-----Original Message-----
From: JC Dill [mailto:jcdill.lists at] 
Sent: Wednesday, September 09, 2009 5:40 PM
To: NANOG list
Subject: Re: Repeated Blacklisting / IP reputation


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. :-)


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.



More information about the NANOG mailing list