Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!usc!wuarchive!zaphod.mps.ohio-state.edu!ub!uhura.cc.rochester.edu!ee.rochester.edu!deke
From: deke@ee.rochester.edu (Dikran Kassabian)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: no inverse mappings
Message-ID: <1990Aug10.152144.17260@ee.rochester.edu>
Date: 10 Aug 90 15:21:44 GMT
Reply-To: deke@ee.rochester.edu (Dikran Kassabian)
Organization: University of Rochester Department of Electrical Engineering
Lines: 27

I see an increasing number of ftp connections to a UNIX box in our domain 
that provides anonymous ftp, and a fair number of telnet connections
from colleagues of the faculty members here.  What's disturbing is that
my log files show a goodly 1/4 of the non-local entries to have no inverse 
mappings... that is to say I see an IP address in the log file rather than 
a FQDN.  I see about 45 such entries from about 20 addresses over the last 
month.  

A brief investigation this morning via nslookup and whois 'net xxx.yyy' tells 
me a bit more; some small percentage of the requests to reverse resolve the
address are timing out or failing to locate the proper server, but the
vast majority are reported as a "Non-existent domain" by nslookup, even though
whois 'net xxx[.yyy[.zzz]]' shows that the non-subnetted network number is
in fact assigned.  In other words, I see lots of what appears to be improperly
handled class C subnets of class B networks -- no inverse mappings, and
perhaps no domain name server at all.

Are others seeing this?  What do you do about it?  Ignore it?  Send mail
to the hostmaster or postmaster of the parent registered net?  How about
refusing such connections altogether when the address doesn't inverse map?
I'm willing to continue ignoring this for now, but I'd like to hear from
others... what is the Right Thing To DO?  I guess I'm hoping someone more 
knowledgeable than I will quote an RFC and make it all better :-\


      ^Deke Kassabian,   deke@ee.rochester.edu   or   ur-valhalla!deke
   Univ of Rochester, Dept of EE, Rochester, NY 14627     (+1 716-275-3106)