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Home > Archive > alt.certification.network-plus > January 2004 > VLSM and Supernetting?
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| Author |
VLSM and Supernetting?
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| Adam Leinss 2004-01-18, 11:24 pm |
| Does anyone have any good resources on Variable Length Subnet Masking
(VLSM) or Supernetting, specifically example problems and solutions?
The book for exam 70-291 (Microsoft Network infrastructure for Windows
2003) gives very little material on each. I only found one sample
problem and solution for VLSM on a college class web site via Google.
Thanks,
Adam
| |
|
| Don't sweat too much about it! This is really not a subject for Network+,
more for a Cisco cert.
This is a descent website if you don't want to buy a book.
http://www.learntcpip.com/
AT
"Adam Leinss" <aleinss@toughguy.net> wrote in message
news:Xns9474E0FBCCDB7aleinssto
ughguynet@toughguy.net...
> Does anyone have any good resources on Variable Length Subnet Masking
> (VLSM) or Supernetting, specifically example problems and solutions?
> The book for exam 70-291 (Microsoft Network infrastructure for Windows
> 2003) gives very little material on each. I only found one sample
> problem and solution for VLSM on a college class web site via Google.
>
> Thanks,
> Adam
| |
| Charles M. Kozierok 2004-01-19, 11:25 am |
| Hi Adam,
In article < Xns9474E0FBCCDB7aleinsstoughgu
ynet@toughguy.net>,
Adam Leinss <aleinss@toughguy.net> wrote:
} Does anyone have any good resources on Variable Length Subnet Masking
} (VLSM) or Supernetting, specifically example problems and solutions?
} The book for exam 70-291 (Microsoft Network infrastructure for Windows
} 2003) gives very little material on each. I only found one sample
} problem and solution for VLSM on a college class web site via Google.
There is very little of this sort of material available for free online
-- I know because I have researched it myself.
I have a fairly comprehensive dscripton of both VLSM and CIDR
(supernetting) along with tons more information on IP addressing in my
new TCP/IP Guide. But it's not free, and I only have one example of VLSM
and one of CIDR (with color illustrations).
If you have any specific questions, fire away.
peace,
-*-
Charles M. Kozierok (mailto:ixlu@PCGuide.com)
Author, The TCP/IP Guide - <http://www.TCPIPGuide.com>
A comprehensive, comprehensible guide to TCP/IP protocols and technologies...
| |
| Charles M. Kozierok 2004-01-19, 11:25 am |
| In article <_GJOb.18920$zj7.17375@newsread1.news.pas.earthlink.net>,
AT <torgny@@direcway.com> wrote:
} Don't sweat too much about it! This is really not a subject for Network+,
} more for a Cisco cert.
Perhaps, but it's essential to understand if you want anything
more than just a piece of paper.
peace,
-*-
Charles M. Kozierok (mailto:ixlu@PCGuide.com)
Author, The TCP/IP Guide - <http://www.TCPIPGuide.com>
A comprehensive, comprehensible guide to TCP/IP protocols and technologies...
| |
| Adam Leinss 2004-01-19, 9:25 pm |
| ixlu@PCGuide.com (Charles M. Kozierok) wrote in
news:bugssl$auj$1@reader2.panix.com:
> I have a fairly comprehensive dscripton of both VLSM and CIDR
> (supernetting) along with tons more information on IP addressing
> in my new TCP/IP Guide. But it's not free, and I only have one
> example of VLSM and one of CIDR (with color illustrations).
>
> If you have any specific questions, fire away.
Here's the one from the college web site on VLSM
You have a network id of 202.128.236.0
You need to support these sub-networks:
- 6 networks with 26 hosts
- 3 networks with 10 hosts
- 4 networks with 2 hosts
The solution given:
202.128.236.0/27 this gives 8 sub-networks with 30 hosts each, but we
only need 6 sub-networks
Now we can split the 2 remaining sub-networks:
202.128.236.0/28 gives 4 sub-networks with 14 hosts each, but we only
need 3
Finally, for the last network, we can use a /30:
202.128.236.0/30 gives 4 sub-networks with 2 hosts each.
I get how he computed the 14 & 2 hosts (just the 2^n-2 formula), but
how the heck does he get 4 sub-networks on each answer? The
Microsoft book has a chart that seems to indicate that you get 1
subnet per each bit that you borrow from the host ID and the number
of hosts decreases with each borrow.
Also, he gives 202.128.236.0 for each sub-network, but this cannot be
correct? The second answer should be 202.128.236.180/28 I think.
I also have a Syngress book on TCP/IP and Illustrated TCP/IP by
Naugle. Both touch on VLSM very little.
Thanks,
Adam
| |
| Charles M. Kozierok 2004-01-19, 9:25 pm |
| In article < Xns9475C46BBBACFaleinsstoughgu
ynet@toughguy.net>,
Adam Leinss <aleinss@toughguy.net> wrote:
} Here's the one from the college web site on VLSM
Okay I Googled this up. It is very poorly explained; to be fair, it was
likely written by someone for whom English was a second (or later)
language. Still, it is very hard to understand, and confused me a great
deal at first.
} You have a network id of 202.128.236.0
The example is a Class C network, so this is really 202.128.236.0/24.
That's important.
} You need to support these sub-networks:
}
} - 6 networks with 26 hosts
} - 3 networks with 10 hosts
} - 4 networks with 2 hosts
}
} The solution given:
}
} 202.128.236.0/27 this gives 8 sub-networks with 30 hosts each, but we
} only need 6 sub-networks
Taking 3 bits from the host ID yields 8 different /27 networks:
202.128.236.0/27
202.128.236.32/27
202.128.236.64/27
202.128.236.96/27
202.128.236.128/27
202.128.236.160/27
202.128.236.192/27
202.128.236.224/27
He is keeping 6 for the nets with 26 hosts, and further dividing two of
them. You are quite right that only one of these is 202.128.236.0/27.
} Now we can split the 2 remaining sub-networks:
}
} 202.128.236.0/28 gives 4 sub-networks with 14 hosts each, but we only
} need 3
}
} Finally, for the last network, we can use a /30:
}
} 202.128.236.0/30 gives 4 sub-networks with 2 hosts each.
This isn't what he means, though I can see why you think this is what he
is saying. Here's how the example works.
Split the /24 (class C) into 8 /27's. Each can have 32 hosts, so save the
last 6 for the 26-host subnets.
Take the 1st /27, 202.128.136.0/27, and take one extra bit to
split it into two /28s: 202.128.136.0/28 and 202.128.136.16/28. Reserve
these for 2 of the 3 10-host subnets.
Take the 2nd /27, 202.128.136.32/27, and split it into two /28s:
202.128.136.32/28 and 202.128.136.48/28. Take the first of these to
satisfy the requirement for the 3rd 10-host network.
Then, take the last /28, 202.128.136.48/28 and take 2 bits to make four /30s:
202.128.136.48/30
202.128.136.52/30
202.128.136.56/30
202.128.136.60/30
Each of these can support 2 hosts.
I excerpted and posted the VLSM explanation from my Guide for your
convenience. I think you'll find it more than a bit easier to
understand. There is also a full (14-page) description of CIDR in the
Guide.
http://www.tcpipguide.com/tcpip_vlsm.pdf
I won't likely be leaving that up indefinitely BTW. 
peace,
-*-
Charles M. Kozierok (mailto:ixlu@PCGuide.com)
Author, The TCP/IP Guide - <http://www.TCPIPGuide.com>
A comprehensive, comprehensible guide to TCP/IP protocols and technologies...
| |
| Tom MacIntyre 2004-01-25, 2:26 pm |
|
In article < Xns9475C46BBBACFaleinsstoughgu
ynet@toughguy.net>,
Adam Leinss <aleinss@toughguy.net> wrote:
} Here's the one from the college web site on VLSM
I always thought this was pretty good, and I see they've updated it
since I last read it, with some IPv6 stuff.
http://www.3com.com/other/pdfs/infr...n_US/501302.pdf
Tom
| |
| Adam Leinss 2004-01-26, 10:26 pm |
| Tom MacIntyre <tom__macintyre@hotmail.com> wrote in
news:df0810djch7v0qor5201umd2u
onqoljiig@4ax.com:
>
> In article < Xns9475C46BBBACFaleinsstoughgu
ynet@toughguy.net>,
> Adam Leinss <aleinss@toughguy.net> wrote:
> } Here's the one from the college web site on VLSM
>
> I always thought this was pretty good, and I see they've updated it
> since I last read it, with some IPv6 stuff.
>
> http://www.3com.com/other/pdfs/infr...n_US/501302.pdf
>
> Tom
Tom, you are most excellent! This is a great guide. Very easy to
follow.
Thanks again!
Adam
| |
| Adam Leinss 2004-01-26, 10:26 pm |
| ixlu@PCGuide.com (Charles M. Kozierok) wrote in
news:bui1p1$nbg$1@reader2.panix.com:
> http://www.tcpipguide.com/tcpip_vlsm.pdf
>
> I won't likely be leaving that up indefinitely BTW.
Crap, I just read this message, is there any possiblity of still
getting the file?
Thanks,
Adam
| |
| Charles M. Kozierok 2004-01-27, 9:26 am |
| In article < Xns947CC6DED6167aleinsstoughgu
ynet@toughguy.net>,
Adam Leinss <aleinss@toughguy.net> wrote:
} ixlu@PCGuide.com (Charles M. Kozierok) wrote in
} news:bui1p1$nbg$1@reader2.panix.com:
}
} > http://www.tcpipguide.com/tcpip_vlsm.pdf
} >
} > I won't likely be leaving that up indefinitely BTW.
}
} Crap, I just read this message, is there any possiblity of still
} getting the file?
I just re-enabled it for you, Adam.
peace,
-*-
Charles M. Kozierok (mailto:ixlu@PCGuide.com)
Author, The TCP/IP Guide - <http://www.TCPIPGuide.com>
A comprehensive, comprehensible guide to TCP/IP protocols and technologies...
| |
| Tom MacIntyre 2004-01-27, 5:25 pm |
| On Tue, 27 Jan 2004 01:34:01 GMT, Adam Leinss <aleinss@toughguy.net>
wrote:
>Tom MacIntyre <tom__macintyre@hotmail.com> wrote in
> news:df0810djch7v0qor5201umd2u
onqoljiig@4ax.com:
>
>
>Tom, you are most excellent! This is a great guide. Very easy to
>follow.
>
>Thanks again!
>Adam
Hey, I didn't write it, I just was lucky enough to remember the name
to be able to Google it. :-)
Tom
| |
| Adam Leinss 2004-01-27, 11:25 pm |
| ixlu@PCGuide.com (Charles M. Kozierok) wrote in news:bv5pd3$8gl$1
@reader2.panix.com:
>
> I just re-enabled it for you, Adam.
>
> peace,
Thank you Charles, I got the file. The example looks very nice!
Thanks a lot for posting this for me. I try to track responses by
Google Groups, but for some reason your postings don't show up, thus my
delay in a response.
Adam
| |
| Charles M. Kozierok 2004-01-28, 1:25 pm |
| In article < Xns947DDEC4A3723aleinsstoughgu
ynet@toughguy.net>,
Adam Leinss <aleinss@toughguy.net> wrote:
} Thank you Charles, I got the file. The example looks very nice!
} Thanks a lot for posting this for me. I try to track responses by
} Google Groups, but for some reason your postings don't show up, thus my
} delay in a response.
Glad you found it helpful, Adam. There's tons more info on IP addressing
and other subjects in the full Guide. 
peace,
-*-
Charles M. Kozierok (mailto:ixlu@PCGuide.com)
Author, The TCP/IP Guide - <http://www.TCPIPGuide.com>
A comprehensive, comprehensible guide to TCP/IP protocols and technologies...
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