Re: IPv6 subnetting primer

From: kelly@cliffhanger.com
Date: Wed Apr 18 2007 - 23:58:54 ART


I need new eyes. You said ipv6.

        lol

Oh well.

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 Impossible Triangle                                                                      
    M. C. Escher 

Quoting Kelly Scroggins <kelly@cliffhanger.com>: 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 _______________________________________________________________________ Subscription information may be found at: http://www.groupstudy.com/list/CCIELab.html _______________________________________________________________________ Subscription information may be found at: http://www.groupstudy.com/list/CCIELab.html _______________________________________________________________________ Subscription information may be found at: http://www.groupstudy.com/list/CCIELab.html



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