Re: [Phpip-support] Understanding CIDR entries and Prefixes

[<php...@li...>]

Hi John,

To answer your question regarding VLSM and CIDR, the difference is that with
VLSM, the recursion is performed on the address space previously assigned to
an organization and is invisible to the global Internet. CIDR, on the other
hand, permits the recursive allocation of an address block by an Internet
Registry to a high-level ISP, to a mid-level ISP, to a low-level ISP, and
finally to a private organization's network
 
They way phpip will use CIDR is to define the address block and then build
the networks within that address block.  You can also apply group based
control over each CIDR block for administration.  CIDR blocks that are less
then /24 will build multiple /24 (256) for easy IP administration. 

Examples;
CIDR block 
10.0.0.0/16 -- Building A
	10.0.1.0/24 1st Floor East
	10.0.2.0/24 1st Floor West
	10.0.3.0/24 2nd Floor East

OR

CIDR block
64.50.56.32/28 -- ISP 1
	64.50.56.32 network
	64.50.56.33 router
	64.50.56.34 host1

To answer you question from below on how to build the following networks.

CIDR block
10.0.0.0/24 (256 ip's) 
 PREFIX => 10.0.0.0/24

CIDR block
10.0.2.0/23  (512 ip's) 
 PREFIX => 10.0.2.0/24
 PREFIX => 10.0.3.0/24

CIDR block
10.0.4.0/22 (1024 ip's) 
 PREFIX => 10.0.4.0/24
 PREFIX => 10.0.5.0/24
 PREFIX => 10.0.6.0/24
 PREFIX => 10.0.7.0/24
 ...

CIDR block
10.0.8.0/21 (2046 ip's) 
 PREFIX => 10.0.8.0/24
 PREFIX => 10.0.9.0/24
 PREFIX => 10.0.10.0/24
 PREFIX => 10.0.11.0/24
 ...

CIDR block
10.0.16.0/20 (4094 ip's') 
 PREFIX => 10.0.16.0/24
 PREFIX => 10.0.17.0/24
 PREFIX => 10.0.18.0/24
 PREFIX => 10.0.19.0/24
 ...

Does this answer your question?

Thanks,

Michael


Michael Earls

http://www.vermeer.org <http://www.vermeer.org/> 
http://www.vermeer.org/pgp
http://www.phpip.net <http://www.phpip.net/> 

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________________________________

From: Dean, John [mailto:joh...@me...] 
Sent: Wednesday, October 25, 2006 1:44 PM
To: php...@li...
Subject: Understanding CIDR entries and Prefixes 



I have some questions about Phpip that are not really addressed in the
documentation. 
Hopefully you can point me in the right direction or to a user forum or
something like that. 

I am having trouble understanding how the CIDR entries and the Prefix
entries relate to each  other.  I wonder if my problem stems from the fact
that our network is really constructed  as VLSM not CIDR and perhaps I do
not understand CIDR well enough...

I know that if I create a CIDR entry for 10.0.0.0/8,  Phpip generates one
Prefix -- 10.0.0 
If I create 10.0.0.0/16 Phpip generate 256 Prefixes -- 10.0.0 through
10.255.0 
If I create 10.0.0.0/24 Phpip generates 65535 Prefixes -- 10.0.0.0 through
10.255.255.0 
As far as I can tell all these entries go into the DB, and as you might
expect some of them they make the prefix related dynamic web pages extremely
LARGE and difficult to deal with.


Let's say the following five sub networks make up the entirety of my network
- how do I get this network described in Phpip?

What CIDR entries must  I create in in order to generate the five (and only
five) correct prefixes and associated ip address pools?

10.0.0.0/24 (256 ip's) 

10.0.2.0/23  (512 ip's) 

10.0.4.0/22 (1024 ip's) 

10.0.8.0/21 (2046 ip's) 

10.0.16.0/20 (4094 ip's') 

This isn't really how my network is constructed, but I think the explanation
of this example will help me understand how this works.

Thanks in advance. 

JD