Re: [cobalt-users] IP blocks

[Allan Liska <priz@xxxxxxxx>]

David,

Why on earth would you say that sounded like a "Steamy Pile of BS" to you,
if you do not know that much about subnetting?  Your provider is
absolutely correct.  All IP blocks that are routed set aside the first and
the last IP in that block as identifiers.

It is important to make a distinction though between routed and non-routed
IPs.  If your box is sitting in a data center somewhere, and there are no
special VLANs, etc to it then if your provider assigns you 16 IPs you can
use all 16.  Of course, this also means that anyone on that network
segment can sniff traffic to your box and find out all sorts of cool
things ;+}.  If you are running over a DSL line, or some sort of network
connection, then the IPs will have to be subnetted, and you lose the frist
and last IP.  Ditto if you are in a data center and the people you are
hosting with know what they are doing and actually create a VLAN for you.

For more information on CIDR blocks and routing, take a look at the
following RFCs:

http://www.rfc-editor.org/rfc/rfc1519.txt
http://www.rfc-editor.org/rfc/rfc2050.txt

Hope this helps.

allan
--
Allan Liska                          
allan@xxxxxxxx			     	
www.priz.net                          
703-443-6754                          
                                      

On Wed, 28 Jun 2000, David Lynch wrote:

> A little off subject, but perhaps useful to other newbies....
> 
> My provider is telling me that for every IP block
> I purchase (they call a "block" 16 ip addresses)
> I have to keep 2 of them as "non-use" IPs... I asked
> why, and got this response:
> 
> "In order to do subneting you need an IP for Broadcast and an IP for
> Internal Networking. Even if you would purchase an entire `class c'
> you would lose 2 ip addresses.  It is my understanding that every block
> requires this type of procedure. Otherwise, the IP's wont be visable."
> 
> This sounds like a steamy pile of BS to me, but I really don't know...
> is there anyone on this list that can enlighten me?  Thanks so much.
>