[isalist] Re: Isa 2004 and CIDR?
- From: "Troy Radtke" <TRadtke@xxxxxxxxxxxx>
- To: <isalist@xxxxxxxxxxxxx>
- Date: Wed, 12 Jul 2006 08:59:49 -0500
http://www.ISAserver.org
-------------------------------------------------------
You can break a block down to 4 address if you like (1 wire, 2 host, 1
broadcast) with a /30 notation. A /29 only has 6 useable address if you
respect the wire and broadcast IP's (some people don't). A /28 will get
you up to 14, a /27 up to 32.
Common ones I use:
CIDR Block Prefix # Equivalent Class C # of Host Addresses
/27 1/8th of a Class C 32 hosts
/26 1/4th of a Class C 64 hosts
/25 1/2 of a Class C 128
hosts
/24 1 Class C 256
hosts
/23 2 Class C 512
hosts
/22 4 Class C 1,024
hosts
/21 8 Class C 2,048
hosts
/20 16 Class C 4,096
hosts
/19 32 Class C 8,192
hosts
/18 64 Class C 16,384
hosts
/17 128 Class C 32,768
hosts
/16 256 Class C 65,536
hosts (= 1 Class B)
/15 512 Class C 131,072
hosts
/14 1,024 Class C 262,144 hosts
/13 2,048 Class C 524,288 hosts
A full table can be found at:
http://64.233.167.104/search?q=cache:cOHigva_Je8J:doc.m0n0.ch/quickstart
wrap/+CIDR+numbers&hl=en&gl=us&ct=clnk&cd=7&client=firefox-a
I'd point you to more references, but we all know how well Cisco based
information is accepted here... =?P
-----Original Message-----
From: isalist-bounce@xxxxxxxxxxxxx [mailto:isalist-bounce@xxxxxxxxxxxxx]
On Behalf Of Ball, Dan
Sent: Wednesday, July 12, 2006 6:26 AM
To: isalist@xxxxxxxxxxxxx
Subject: [isalist] Re: Isa 2004 and CIDR?
http://www.ISAserver.org
-------------------------------------------------------
Yes, you should be able to do that with no problem. Per RFC 1918
(http://tools.ietf.org/html/1918), the 192.168.x.x subnet is a group of
256 "contiguous" class C address blocks. Using a subnet mask in this
situation would allow you to use those "contiguous" subnets as one.
Since they are "contiguous", it is the equivalent of a Class B block in
the Class C section.
-----Original Message-----
From: isalist-bounce@xxxxxxxxxxxxx [mailto:isalist-bounce@xxxxxxxxxxxxx]
On Behalf Of Taps
Sent: Tuesday, July 11, 2006 9:48 PM
To: isalist@xxxxxxxxxxxxx
Subject: [isalist] Isa 2004 and CIDR?
http://www.ISAserver.org
-------------------------------------------------------
I know this is going to sound like a silly question, but I cant find any
information confirming or denying this:
We are currently using a 192.168.140.0/24 subnet in our internal
network. Recently, we have started using VMWare to do support of some
of our customers. We like to have duplicate setups of their servers in
our virtual environment. At the extreme, our customers have 7 separate
servers per site which we duplicate. We have recently acquired many new
customers and about half our what we term "multi-site". So there is a
possiblity of 14 or 21 servers. Each of which needing a static IP
address (because of the stupid way the software is written).
With the addition of these, plus the rest of our network, we are running
out of IP Addresses. I am thinking of dropping the subnet mask back to
a /23 or /22. To give me a usable range of
192.168.140.1-192.168.143.254.
I realizing because of CIDR, the theory of 192.x.x.x needing to be a
classC isnt an absolute anymore. But before I go through and make any
changes, I was wondering if anyone could confirm or deny that ISA will
handle this without any major issues.
Before you ask, yes, I plan on testing this before I roll it out. But
that wont be for a while. I figured if anyone had tried something
similar they could clue me in on any issues that they might have had.
If someone has tried it and it just wont work, then I will find another
alternative.
And yes, switching to a 10.x.x.x address was considered. But again,
with the way some of the software was written, the IP addresses would
need to stay the same.
--
Taps@xxxxxxxxxxxx
http://Taps.Iniquity.Org
- "What spirit is so empty and blind, that it cannot recognize the fact
that the foot is more noble than the shoe, and skin more beautiful than
the garment with which it is clothed?"
-- Michaelangelo
- "Build a man a fire, and he'll be warm for a day. Set a man on fire,
and he'll be warm for the rest of his life."
-- Terry Pratchett
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