Re: IP address allocation

["Scott M. Algatt" <salgatt () turtleshell net>]

This is totally up to the ISP itself.  They may have had the block
previously allocated to something else that they did reverse DNS for.

They may also do reverse DNS for sanity sake.  Lots of ISPs give a
location and other information as to where the IP is allocated.  For
instance, comcast has: 68.82.4.14

This IP resolves back to

pcp01631289pcs.tybout01.de.comcast.net

the de signifies that the IP is in Delaware.  I don't know the rest but it
helps them identify the region that the IP is allocated.


Regards,

Scott M. Algatt

Behold the turtle. He makes progress only when he sticks his neck out.

On Thu, 31 Jul 2003, Terry wrote:

> 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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