From: kelly@cliffhanger.com
Date: Wed Apr 18 2007 - 23:42:25 ART
This book may help you. It sort of teaches along
the lines that I understand it. I'm not a math
expert or a subnetting expert, I'm just coping :)
TCP/IP Addressing
Designing and Optimizing your IP Addressing Scheme
by Buck Graham
http://www.amazon.com/Tcp-Ip-Addressing-Designing-Optimizing/dp/0122950216
I found that book after coming to conclusions I
explain below. I haven't read it thoroughly but
as I glance through it, I see what appears to be
the same conceptual view I've come to terms with.
My understanding, or way of thinking about
subnetting ipv4 is summarized in the links below.
I'll try to interpret a little bit (below) as
well.
Take a look at these web pages I created. I refer
to them in the text that follows below.
IP Address Planning
http://home1.gte.net/res0psau/addr-tool-kit-frames.html
Bits, Masks and Hosts
http://home1.gte.net/res0psau/bits-masks-hosts.html
The top table has four rows with represent the
CIDR masks in each octet of the IP address.
i.e.,
one.two.three.four
One | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8
Two | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16
Three | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24
Four | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32
Mask | 128 | 192 | 224 | 240 | 248 | 252 | 254 | 255
Wildcard | 127 | 63 | 31 | 15 | 7 | 3 | 1 | 0
Hosts | 126 | 62 | 30 | 14 | 6 | 2 | 0 | n/a
Bit Value | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
If you have a /25, and change it to a /26, you can
see that the number of hosts in each subnet are
split in half.
Likewise, if you have a /26 and you change it to a
/25, the number of hosts in each subnet double.
If you look closely, you can see this applies to
the number of 'nets' (subnets) as well as the
number of hosts within a subnet.
The last row of the second table (Bit Value),
is a multiple for the incremental increase in
subnets.
For example, if you have a /17, the first subnet
is '0'.
1.1.0.0/17
The next subnet will be '0+128'
1.1.128.0/17
Then the next subnet will be 128+128 which equals
256. But we don't have a '256' subnet. So we
only have two nets.
The same thing applies to ....say, /18. In this
case, the subnets will increment by 64.
1.1.0.0/18 The first subent is 0
1.1.64.0/18 (0+64=64)
1.1.128.0/18 (64+64=128)
1.1.192.0/18 (64+128=192)
The first link in this msg (IP Address Planning)
will deomonstrate what I've explained above. Look
at the table on the right side of the browser
window.
So to summarize, in general ...It's just halving
and doubling. like opening or closing the apeture
(fstop) of a camera lens.
Moving the mask one bit to the right,
from /25 to /26...
splits the network in half,
from 128 hosts to 64 hosts per network
and doubles the number of networks.
... from /26 to /27,
cuts the number of hosts in half,
from 63 to 31 per network
and doubles the number of networks
from 4, to 8.
Moving the mask one bit to the left,
from /17 to /18...
doubles the number of hosts in each network,
from 64 to 128
and splits the number of networks in half,
from 128 to 64.
... from /18 to /19,
spilts the number of hosts in each subnet in
half, from 62 to 30.
And doubles the number of networks
from 4 to 8.
--
___
/\ \
/ \ \
/ \ \
/ /\ \ \
/ / \ \ \
/ / / \ \ \
/ / /___\__\ \
/ / /___________\
\/_______________/
Impossible Triangle
M. C. Escher
Quoting Victor Cappuccio <victor@ccbootcamp.com>:
This this one
http://www.ccbootcamp.com/download/Files-for-NLIs-CCIE-IPV6-Lab-Guide/
thanks,
Victor Cappuccio.-
Network Learning Inc - A Cisco Sponsored Organization (SO) YES! We take
Cisco Learning credits!
victor@ccbootcamp.com
http://www.ccbootcamp.com (Cisco Training and Rental Racks)
http://www.ccbootcamp.com/groupstudy.html (groupstudy member discounts!)
Voice: 702-968-5100
FAX: 702-446-8012
-----Original Message-----
From: nobody@groupstudy.com on behalf of Matt Sherman
Sent: Wed 4/18/2007 13:33
To: ccielab@groupstudy.com
Subject: IPv6 subnetting primer
Hello,
Does anyone out there have a good tutorial on IPv6 subnetting? I've read a
lot of stuff online but the light bulb has not gone off in my head yet.
Thanks,
Matt
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