RE: IP address allocation

["Brad Hill - Quonic" <brad () quonic com>]

It may depend on the kind of ISP you're dealing with. DSL/Cable
providers seem to assigning generic DNS entries such as
host01.client.com, host02.client.com, etc for every IP address in a
block. I believe most ISP's offering leased lines will do the same
however they will usually change the DNS entries if requested. The
alternative would be to manage your own DNS.

To answer your question more directly: Yes, most ISP's will assign
generic DNS entries for all IP's in a block regardless of whether or not
they are currently in use.

__
Brad Hill
brad () quonic com



> -----Original Message-----
> From: Terry [mailto:tech () futurecourse com]
> Sent: Thursday, July 31, 2003 5:41 AM
> 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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