RE: IP address allocation

["David Gillett" <gillettdavid () fhda edu>]

  For a while it was common for some servers to reject connections 
from IP addresses that didn't resolve via reverse DNS(*).  Since 
delegating reverse DNS along other than Class C boundaries is a 
real pain (not impossible, but all 3 ways to do it count as 
kludges...), an ISP that does it for any of its space might as 
well do it for all.
  (*) I don't recall the exact rationale, and it has been a while
since I've seen any discussion of it.

David Gillett


> -----Original Message-----
> From: Terry [mailto:tech () futurecourse com]
> Sent: July 31, 2003 02:41
> To: security-basics () securityfocus com
> Subject: IP address allocation
>
>
> Hi,
>
> I've googled but haven't really come across anything that answers my
> questions.  Is it common practice for ISPs to allocate a block of
> addresses to a customer and put in DNS records for ones that are
> unused?
>
> For example, xxx.8-xxx.15 is assigned to the customer.  Customer uses
> xxx.9 for the router and xxx.10 for web server.  xxx.11-14 are unused.
> I would expect to see DNS records for xxx.9 and xxx.10 but not for the
> rest of the block.  Am I wrong?  If there are DNS records for the rest
> of the IPs, why is that?  Is there some security reason for doing
> this?
>
> -- 
> Regards,
> Terry
>
>
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